[libc-commits] [libc] [libc] Add printf error handling (PR #162876)
Marcell Leleszi via libc-commits
libc-commits at lists.llvm.org
Fri Oct 10 09:06:57 PDT 2025
https://github.com/mleleszi updated https://github.com/llvm/llvm-project/pull/162876
>From 25c7d79a96f2ee0db4c49ee4854c3ae986394dda Mon Sep 17 00:00:00 2001
From: Marcell Leleszi <mleleszi at google.com>
Date: Tue, 7 Oct 2025 06:16:51 +0000
Subject: [PATCH 01/13] Change writer to store chars written as size_t
---
libc/src/stdio/printf_core/printf_main.h | 3 ++-
libc/src/stdio/printf_core/write_int_converter.h | 4 ++--
libc/src/stdio/printf_core/writer.h | 8 ++++----
libc/src/stdlib/strfromd.cpp | 3 ++-
libc/src/stdlib/strfromf.cpp | 3 ++-
libc/src/stdlib/strfroml.cpp | 3 ++-
6 files changed, 14 insertions(+), 10 deletions(-)
diff --git a/libc/src/stdio/printf_core/printf_main.h b/libc/src/stdio/printf_core/printf_main.h
index 57f29858d5298..c654571d1dffd 100644
--- a/libc/src/stdio/printf_core/printf_main.h
+++ b/libc/src/stdio/printf_core/printf_main.h
@@ -38,7 +38,8 @@ int printf_main(Writer<write_mode> *writer, const char *__restrict str,
return result;
}
- return writer->get_chars_written();
+ // TODO overflow
+ return static_cast<int>(writer->get_chars_written());
}
} // namespace printf_core
diff --git a/libc/src/stdio/printf_core/write_int_converter.h b/libc/src/stdio/printf_core/write_int_converter.h
index efcff278bd284..04b2bef05bc7b 100644
--- a/libc/src/stdio/printf_core/write_int_converter.h
+++ b/libc/src/stdio/printf_core/write_int_converter.h
@@ -29,11 +29,11 @@ LIBC_INLINE int convert_write_int(Writer<write_mode> *writer,
return NULLPTR_WRITE_ERROR;
#endif // LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
- int written = writer->get_chars_written();
+ size_t written = writer->get_chars_written();
switch (to_conv.length_modifier) {
case LengthModifier::none:
- *reinterpret_cast<int *>(to_conv.conv_val_ptr) = written;
+ *reinterpret_cast<int *>(to_conv.conv_val_ptr) = static_cast<int>(written);
break;
case LengthModifier::l:
*reinterpret_cast<long *>(to_conv.conv_val_ptr) = written;
diff --git a/libc/src/stdio/printf_core/writer.h b/libc/src/stdio/printf_core/writer.h
index 1d4734a51b9b8..9de108ece510f 100644
--- a/libc/src/stdio/printf_core/writer.h
+++ b/libc/src/stdio/printf_core/writer.h
@@ -127,7 +127,7 @@ template <WriteMode write_mode> struct WriteBuffer {
template <WriteMode write_mode> class Writer final {
WriteBuffer<write_mode> &wb;
- int chars_written = 0;
+ size_t chars_written = 0;
LIBC_INLINE int pad(char new_char, size_t length) {
// First, fill as much of the buffer as possible with the padding char.
@@ -161,7 +161,7 @@ template <WriteMode write_mode> class Writer final {
// Takes a string, copies it into the buffer if there is space, else passes it
// to the overflow mechanism to be handled separately.
LIBC_INLINE int write(cpp::string_view new_string) {
- chars_written += static_cast<int>(new_string.size());
+ chars_written += new_string.size();
if (LIBC_LIKELY(wb.buff_cur + new_string.size() <= wb.buff_len)) {
inline_memcpy(wb.buff + wb.buff_cur, new_string.data(),
new_string.size());
@@ -175,7 +175,7 @@ template <WriteMode write_mode> class Writer final {
// if there is space, else calls pad which will loop and call the overflow
// mechanism on a secondary buffer.
LIBC_INLINE int write(char new_char, size_t length) {
- chars_written += static_cast<int>(length);
+ chars_written += length;
if (LIBC_LIKELY(wb.buff_cur + length <= wb.buff_len)) {
inline_memset(wb.buff + wb.buff_cur, static_cast<unsigned char>(new_char),
@@ -199,7 +199,7 @@ template <WriteMode write_mode> class Writer final {
return wb.overflow_write(char_string_view);
}
- LIBC_INLINE int get_chars_written() { return chars_written; }
+ LIBC_INLINE size_t get_chars_written() { return chars_written; }
};
// Class-template auto deduction helpers.
diff --git a/libc/src/stdlib/strfromd.cpp b/libc/src/stdlib/strfromd.cpp
index f51e6d4c7f1df..c0989f1a97dca 100644
--- a/libc/src/stdlib/strfromd.cpp
+++ b/libc/src/stdlib/strfromd.cpp
@@ -36,7 +36,8 @@ LLVM_LIBC_FUNCTION(int, strfromd,
if (n > 0)
wb.buff[wb.buff_cur] = '\0';
- return writer.get_chars_written();
+ // TODO overflow
+ return static_cast<int>(writer.get_chars_written());
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdlib/strfromf.cpp b/libc/src/stdlib/strfromf.cpp
index 14dbfdb25bab6..01090c997af1b 100644
--- a/libc/src/stdlib/strfromf.cpp
+++ b/libc/src/stdlib/strfromf.cpp
@@ -36,7 +36,8 @@ LLVM_LIBC_FUNCTION(int, strfromf,
if (n > 0)
wb.buff[wb.buff_cur] = '\0';
- return writer.get_chars_written();
+ // TODO overflow
+ return static_cast<int>(writer.get_chars_written());
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdlib/strfroml.cpp b/libc/src/stdlib/strfroml.cpp
index 12f22a8a2fb65..436243d1e1c38 100644
--- a/libc/src/stdlib/strfroml.cpp
+++ b/libc/src/stdlib/strfroml.cpp
@@ -41,7 +41,8 @@ LLVM_LIBC_FUNCTION(int, strfroml,
if (n > 0)
wb.buff[wb.buff_cur] = '\0';
- return writer.get_chars_written();
+ // TODO overflow
+ return static_cast<int>(writer.get_chars_written());
}
} // namespace LIBC_NAMESPACE_DECL
>From 362c00e1c89faafbff7605233bb752447491a7be Mon Sep 17 00:00:00 2001
From: Marcell Leleszi <mleleszi at google.com>
Date: Tue, 7 Oct 2025 06:34:43 +0000
Subject: [PATCH 02/13] Prinf internals: use -errno as return values rather
than custrom error values
---
libc/src/stdio/printf_core/core_structs.h | 12 ++++++------
libc/src/stdio/printf_core/fixed_converter.h | 3 ++-
libc/src/stdio/printf_core/int_converter.h | 3 ++-
libc/src/stdio/printf_core/vasprintf_internal.h | 5 +++--
libc/src/stdio/printf_core/vfprintf_internal.h | 3 ++-
libc/src/stdio/printf_core/write_int_converter.h | 3 ++-
6 files changed, 17 insertions(+), 12 deletions(-)
diff --git a/libc/src/stdio/printf_core/core_structs.h b/libc/src/stdio/printf_core/core_structs.h
index e27f77b6b594a..83e251a3b1da5 100644
--- a/libc/src/stdio/printf_core/core_structs.h
+++ b/libc/src/stdio/printf_core/core_structs.h
@@ -134,12 +134,12 @@ template <typename T> LIBC_INLINE constexpr TypeDesc type_desc_from_type() {
constexpr int WRITE_OK = 0;
// These are the printf return values for when an error has occurred. They are
// all negative, and should be distinct.
-constexpr int FILE_WRITE_ERROR = -1;
-constexpr int FILE_STATUS_ERROR = -2;
-constexpr int NULLPTR_WRITE_ERROR = -3;
-constexpr int INT_CONVERSION_ERROR = -4;
-constexpr int FIXED_POINT_CONVERSION_ERROR = -5;
-constexpr int ALLOCATION_ERROR = -6;
+// constexpr int FILE_WRITE_ERROR = -1;
+// constexpr int FILE_STATUS_ERROR = -2;
+// constexpr int NULLPTR_WRITE_ERROR = -3;
+// constexpr int INT_CONVERSION_ERROR = -4;
+// constexpr int FIXED_POINT_CONVERSION_ERROR = -5;
+// constexpr int ALLOCATION_ERROR = -6;
} // namespace printf_core
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/printf_core/fixed_converter.h b/libc/src/stdio/printf_core/fixed_converter.h
index e8a3314967562..a7185dcb11d8a 100644
--- a/libc/src/stdio/printf_core/fixed_converter.h
+++ b/libc/src/stdio/printf_core/fixed_converter.h
@@ -20,6 +20,7 @@
#include "src/stdio/printf_core/converter_utils.h"
#include "src/stdio/printf_core/core_structs.h"
#include "src/stdio/printf_core/writer.h"
+#include "hdr/errno_macros.h"
#include <inttypes.h>
#include <stddef.h>
@@ -59,7 +60,7 @@ LIBC_INLINE constexpr uint32_t const_ten_exp(uint32_t exponent) {
READ_FX_BITS(unsigned LENGTH_MODIFIER accum); \
} else { \
LIBC_ASSERT(false && "Invalid conversion name passed to convert_fixed"); \
- return FIXED_POINT_CONVERSION_ERROR; \
+ return -EINVAL; \
} \
} while (false)
diff --git a/libc/src/stdio/printf_core/int_converter.h b/libc/src/stdio/printf_core/int_converter.h
index 11234c32ce997..08e27e1a60447 100644
--- a/libc/src/stdio/printf_core/int_converter.h
+++ b/libc/src/stdio/printf_core/int_converter.h
@@ -17,6 +17,7 @@
#include "src/stdio/printf_core/converter_utils.h"
#include "src/stdio/printf_core/core_structs.h"
#include "src/stdio/printf_core/writer.h"
+#include "hdr/errno_macros.h"
#include <inttypes.h>
#include <stddef.h>
@@ -91,7 +92,7 @@ LIBC_INLINE int convert_int(Writer<write_mode> *writer,
cpp::array<char, details::num_buf_size()> buf;
auto str = details::num_to_strview(num, buf, to_conv.conv_name);
if (!str)
- return INT_CONVERSION_ERROR;
+ return -ERANGE;
size_t digits_written = str->size();
diff --git a/libc/src/stdio/printf_core/vasprintf_internal.h b/libc/src/stdio/printf_core/vasprintf_internal.h
index 283d8df2810fb..4e868edca1a1e 100644
--- a/libc/src/stdio/printf_core/vasprintf_internal.h
+++ b/libc/src/stdio/printf_core/vasprintf_internal.h
@@ -6,6 +6,7 @@
//
//===----------------------------------------------------------------------===//
+#include "hdr/errno_macros.h"
#include "hdr/func/free.h"
#include "hdr/func/malloc.h"
#include "hdr/func/realloc.h"
@@ -29,7 +30,7 @@ LIBC_INLINE int resize_overflow_hook(cpp::string_view new_str, void *target) {
if (new_buff == nullptr) {
if (wb->buff != wb->init_buff)
free(wb->buff);
- return printf_core::ALLOCATION_ERROR;
+ return -ENOMEM;
}
if (isBuffOnStack)
inline_memcpy(new_buff, wb->buff, wb->buff_cur);
@@ -57,7 +58,7 @@ LIBC_INLINE int vasprintf_internal(char **ret, const char *__restrict format,
if (wb.buff == init_buff_on_stack) {
*ret = static_cast<char *>(malloc(ret_val + 1));
if (ret == nullptr)
- return printf_core::ALLOCATION_ERROR;
+ return -ENOMEM;
inline_memcpy(*ret, wb.buff, ret_val);
} else {
*ret = wb.buff;
diff --git a/libc/src/stdio/printf_core/vfprintf_internal.h b/libc/src/stdio/printf_core/vfprintf_internal.h
index 630de9d9d43dd..552f2a2f5e34d 100644
--- a/libc/src/stdio/printf_core/vfprintf_internal.h
+++ b/libc/src/stdio/printf_core/vfprintf_internal.h
@@ -9,6 +9,7 @@
#ifndef LLVM_LIBC_SRC_STDIO_PRINTF_CORE_VFPRINTF_INTERNAL_H
#define LLVM_LIBC_SRC_STDIO_PRINTF_CORE_VFPRINTF_INTERNAL_H
+#include "hdr/errno_macros.h"
#include "src/__support/File/file.h"
#include "src/__support/arg_list.h"
#include "src/__support/macros/attributes.h" // For LIBC_INLINE
@@ -63,7 +64,7 @@ LIBC_INLINE int file_write_hook(cpp::string_view new_str, void *fp) {
size_t written = internal::fwrite_unlocked(new_str.data(), sizeof(char),
new_str.size(), target_file);
if (written != new_str.size() || internal::ferror_unlocked(target_file))
- return FILE_WRITE_ERROR;
+ return -EIO;
return WRITE_OK;
}
diff --git a/libc/src/stdio/printf_core/write_int_converter.h b/libc/src/stdio/printf_core/write_int_converter.h
index 04b2bef05bc7b..15c32d9ac272a 100644
--- a/libc/src/stdio/printf_core/write_int_converter.h
+++ b/libc/src/stdio/printf_core/write_int_converter.h
@@ -12,6 +12,7 @@
#include "src/__support/macros/config.h"
#include "src/stdio/printf_core/core_structs.h"
#include "src/stdio/printf_core/writer.h"
+#include "hdr/errno_macros.h"
#include <inttypes.h>
#include <stddef.h>
@@ -26,7 +27,7 @@ LIBC_INLINE int convert_write_int(Writer<write_mode> *writer,
#ifndef LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
// This is an additional check added by LLVM-libc.
if (to_conv.conv_val_ptr == nullptr)
- return NULLPTR_WRITE_ERROR;
+ return -EINVAL;
#endif // LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
size_t written = writer->get_chars_written();
>From f8c75692e43cbb7de691188a8b52f9392b096cf0 Mon Sep 17 00:00:00 2001
From: Marcell Leleszi <mleleszi at google.com>
Date: Tue, 7 Oct 2025 07:07:25 +0000
Subject: [PATCH 03/13] Refactor printf family functions to use PrintfResult
---
libc/src/stdio/asprintf.cpp | 13 +++++++++++--
libc/src/stdio/generic/fprintf.cpp | 13 +++++++++++--
libc/src/stdio/generic/printf.cpp | 13 +++++++++++--
libc/src/stdio/generic/vfprintf.cpp | 13 +++++++++++--
libc/src/stdio/generic/vprintf.cpp | 13 +++++++++++--
libc/src/stdio/printf_core/core_structs.h | 12 ++++++++++++
libc/src/stdio/printf_core/printf_main.h | 9 ++++-----
libc/src/stdio/printf_core/vasprintf_internal.h | 12 ++++++------
libc/src/stdio/printf_core/vfprintf_internal.h | 6 +++---
libc/src/stdio/snprintf.cpp | 14 ++++++++++++--
libc/src/stdio/sprintf.cpp | 14 ++++++++++++--
libc/src/stdio/vasprintf.cpp | 11 ++++++++++-
libc/src/stdio/vsnprintf.cpp | 14 ++++++++++++--
libc/src/stdio/vsprintf.cpp | 13 +++++++++++--
14 files changed, 137 insertions(+), 33 deletions(-)
diff --git a/libc/src/stdio/asprintf.cpp b/libc/src/stdio/asprintf.cpp
index f8cfb74ce48ea..d392c658b898c 100644
--- a/libc/src/stdio/asprintf.cpp
+++ b/libc/src/stdio/asprintf.cpp
@@ -22,8 +22,17 @@ LLVM_LIBC_FUNCTION(int, asprintf,
// and pointer semantics, as well as handling
// destruction automatically.
va_end(vlist);
- int ret = printf_core::vasprintf_internal(buffer, format, args);
- return ret;
+ auto ret_val = printf_core::vasprintf_internal(buffer, format, args);
+ if (ret_val.has_error()) {
+ libc_errno = ret_val.error;
+ return -1;
+ }
+ if (ret_val.value > cpp::numeric_limits<int>::max()) {
+ libc_errno = EOVERFLOW;
+ return -1;
+ }
+
+ return static_cast<int>(ret_val.value);
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/generic/fprintf.cpp b/libc/src/stdio/generic/fprintf.cpp
index 087aeadfc52c5..64d6694770e4e 100644
--- a/libc/src/stdio/generic/fprintf.cpp
+++ b/libc/src/stdio/generic/fprintf.cpp
@@ -27,8 +27,17 @@ LLVM_LIBC_FUNCTION(int, fprintf,
// and pointer semantics, as well as handling
// destruction automatically.
va_end(vlist);
- int ret_val = printf_core::vfprintf_internal(stream, format, args);
- return ret_val;
+ auto ret_val = printf_core::vfprintf_internal(stream, format, args);
+ if (ret_val.has_error()) {
+ libc_errno = ret_val.error;
+ return -1;
+ }
+ if (ret_val.value > cpp::numeric_limits<int>::max()) {
+ libc_errno = EOVERFLOW;
+ return -1;
+ }
+
+ return static_cast<int>(ret_val.value);
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/generic/printf.cpp b/libc/src/stdio/generic/printf.cpp
index bb7c7c86f843f..0020cce2359e8 100644
--- a/libc/src/stdio/generic/printf.cpp
+++ b/libc/src/stdio/generic/printf.cpp
@@ -31,9 +31,18 @@ LLVM_LIBC_FUNCTION(int, printf, (const char *__restrict format, ...)) {
// and pointer semantics, as well as handling
// destruction automatically.
va_end(vlist);
- int ret_val = printf_core::vfprintf_internal(
+ auto ret_val = printf_core::vfprintf_internal(
reinterpret_cast<::FILE *>(PRINTF_STDOUT), format, args);
- return ret_val;
+ if (ret_val.has_error()) {
+ libc_errno = ret_val.error;
+ return -1;
+ }
+ if (ret_val.value > cpp::numeric_limits<int>::max()) {
+ libc_errno = EOVERFLOW;
+ return -1;
+ }
+
+ return static_cast<int>(ret_val.value);
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/generic/vfprintf.cpp b/libc/src/stdio/generic/vfprintf.cpp
index 01f4265f118a6..6311318862bd6 100644
--- a/libc/src/stdio/generic/vfprintf.cpp
+++ b/libc/src/stdio/generic/vfprintf.cpp
@@ -24,8 +24,17 @@ LLVM_LIBC_FUNCTION(int, vfprintf,
internal::ArgList args(vlist); // This holder class allows for easier copying
// and pointer semantics, as well as handling
// destruction automatically.
- int ret_val = printf_core::vfprintf_internal(stream, format, args);
- return ret_val;
+ auto ret_val = printf_core::vfprintf_internal(stream, format, args);
+ if (ret_val.has_error()) {
+ libc_errno = ret_val.error;
+ return -1;
+ }
+ if (ret_val.value > cpp::numeric_limits<int>::max()) {
+ libc_errno = EOVERFLOW;
+ return -1;
+ }
+
+ return static_cast<int>(ret_val.value);
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/generic/vprintf.cpp b/libc/src/stdio/generic/vprintf.cpp
index 08d71515646ed..73b9701ee2eda 100644
--- a/libc/src/stdio/generic/vprintf.cpp
+++ b/libc/src/stdio/generic/vprintf.cpp
@@ -29,9 +29,18 @@ LLVM_LIBC_FUNCTION(int, vprintf,
internal::ArgList args(vlist); // This holder class allows for easier copying
// and pointer semantics, as well as handling
// destruction automatically.
- int ret_val = printf_core::vfprintf_internal(
+ auto ret_val = printf_core::vfprintf_internal(
reinterpret_cast<::FILE *>(PRINTF_STDOUT), format, args);
- return ret_val;
+ if (ret_val.has_error()) {
+ libc_errno = ret_val.error;
+ return -1;
+ }
+ if (ret_val.value > cpp::numeric_limits<int>::max()) {
+ libc_errno = EOVERFLOW;
+ return -1;
+ }
+
+ return static_cast<int>(ret_val.value);
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/printf_core/core_structs.h b/libc/src/stdio/printf_core/core_structs.h
index 83e251a3b1da5..e397e4a5b3abe 100644
--- a/libc/src/stdio/printf_core/core_structs.h
+++ b/libc/src/stdio/printf_core/core_structs.h
@@ -22,6 +22,18 @@
namespace LIBC_NAMESPACE_DECL {
namespace printf_core {
+struct PrintfResult {
+ size_t value;
+ int error;
+
+ constexpr PrintfResult(size_t val) : value(val), error(0) {}
+ constexpr PrintfResult(size_t val, int error) : value(val), error(error) {}
+
+ constexpr bool has_error() { return error != 0; }
+
+ constexpr operator size_t() { return value; }
+};
+
// These length modifiers match the length modifiers in the format string, which
// is why they are formatted differently from the rest of the file.
enum class LengthModifier { hh, h, l, ll, j, z, t, L, w, wf, none };
diff --git a/libc/src/stdio/printf_core/printf_main.h b/libc/src/stdio/printf_core/printf_main.h
index c654571d1dffd..6a9c9a00265d1 100644
--- a/libc/src/stdio/printf_core/printf_main.h
+++ b/libc/src/stdio/printf_core/printf_main.h
@@ -22,7 +22,7 @@ namespace LIBC_NAMESPACE_DECL {
namespace printf_core {
template <WriteMode write_mode>
-int printf_main(Writer<write_mode> *writer, const char *__restrict str,
+PrintfResult printf_main(Writer<write_mode> *writer, const char *__restrict str,
internal::ArgList &args) {
Parser<internal::ArgList> parser(str, args);
int result = 0;
@@ -35,11 +35,10 @@ int printf_main(Writer<write_mode> *writer, const char *__restrict str,
result = writer->write(cur_section.raw_string);
if (result < 0)
- return result;
+ return {0, -result};
}
-
- // TODO overflow
- return static_cast<int>(writer->get_chars_written());
+
+ return writer->get_chars_written();
}
} // namespace printf_core
diff --git a/libc/src/stdio/printf_core/vasprintf_internal.h b/libc/src/stdio/printf_core/vasprintf_internal.h
index 4e868edca1a1e..bfc02fedf5244 100644
--- a/libc/src/stdio/printf_core/vasprintf_internal.h
+++ b/libc/src/stdio/printf_core/vasprintf_internal.h
@@ -43,7 +43,7 @@ LIBC_INLINE int resize_overflow_hook(cpp::string_view new_str, void *target) {
constexpr size_t DEFAULT_BUFFER_SIZE = 200;
-LIBC_INLINE int vasprintf_internal(char **ret, const char *__restrict format,
+LIBC_INLINE PrintfResult vasprintf_internal(char **ret, const char *__restrict format,
internal::ArgList args) {
char init_buff_on_stack[DEFAULT_BUFFER_SIZE];
printf_core::WriteBuffer<Mode<WriteMode::RESIZE_AND_FILL_BUFF>::value> wb(
@@ -51,19 +51,19 @@ LIBC_INLINE int vasprintf_internal(char **ret, const char *__restrict format,
printf_core::Writer writer(wb);
auto ret_val = printf_core::printf_main(&writer, format, args);
- if (ret_val < 0) {
+ if (ret_val.has_error()) {
*ret = nullptr;
- return -1;
+ return ret_val;
}
if (wb.buff == init_buff_on_stack) {
- *ret = static_cast<char *>(malloc(ret_val + 1));
+ *ret = static_cast<char *>(malloc(ret_val.value + 1));
if (ret == nullptr)
return -ENOMEM;
- inline_memcpy(*ret, wb.buff, ret_val);
+ inline_memcpy(*ret, wb.buff, ret_val.value);
} else {
*ret = wb.buff;
}
- (*ret)[ret_val] = '\0';
+ (*ret)[ret_val.value] = '\0'; // TODO OK HERE or overflow
return ret_val;
}
} // namespace printf_core
diff --git a/libc/src/stdio/printf_core/vfprintf_internal.h b/libc/src/stdio/printf_core/vfprintf_internal.h
index 552f2a2f5e34d..71a85077e92b8 100644
--- a/libc/src/stdio/printf_core/vfprintf_internal.h
+++ b/libc/src/stdio/printf_core/vfprintf_internal.h
@@ -68,7 +68,7 @@ LIBC_INLINE int file_write_hook(cpp::string_view new_str, void *fp) {
return WRITE_OK;
}
-LIBC_INLINE int vfprintf_internal(::FILE *__restrict stream,
+LIBC_INLINE PrintfResult vfprintf_internal(::FILE *__restrict stream,
const char *__restrict format,
internal::ArgList &args) {
constexpr size_t BUFF_SIZE = 1024;
@@ -77,10 +77,10 @@ LIBC_INLINE int vfprintf_internal(::FILE *__restrict stream,
buffer, BUFF_SIZE, &file_write_hook, reinterpret_cast<void *>(stream));
Writer writer(wb);
internal::flockfile(stream);
- int retval = printf_main(&writer, format, args);
+ auto retval = printf_main(&writer, format, args);
int flushval = wb.overflow_write("");
if (flushval != WRITE_OK)
- retval = flushval;
+ retval.error = -flushval;
internal::funlockfile(stream);
return retval;
}
diff --git a/libc/src/stdio/snprintf.cpp b/libc/src/stdio/snprintf.cpp
index c8940862f711f..8c22935b849a0 100644
--- a/libc/src/stdio/snprintf.cpp
+++ b/libc/src/stdio/snprintf.cpp
@@ -32,10 +32,20 @@ LLVM_LIBC_FUNCTION(int, snprintf,
wb(buffer, (buffsz > 0 ? buffsz - 1 : 0));
printf_core::Writer writer(wb);
- int ret_val = printf_core::printf_main(&writer, format, args);
+ auto ret_val = printf_core::printf_main(&writer, format, args);
+ if (ret_val.has_error()) {
+ libc_errno = ret_val.error;
+ return -1;
+ }
if (buffsz > 0) // if the buffsz is 0 the buffer may be a null pointer.
wb.buff[wb.buff_cur] = '\0';
- return ret_val;
+
+ if (ret_val.value > cpp::numeric_limits<int>::max()) {
+ libc_errno = EOVERFLOW;
+ return -1;
+ }
+
+ return static_cast<int>(ret_val.value);
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/sprintf.cpp b/libc/src/stdio/sprintf.cpp
index 7be97d3591aaf..2557197894bec 100644
--- a/libc/src/stdio/sprintf.cpp
+++ b/libc/src/stdio/sprintf.cpp
@@ -33,9 +33,19 @@ LLVM_LIBC_FUNCTION(int, sprintf,
wb(buffer, cpp::numeric_limits<size_t>::max());
printf_core::Writer writer(wb);
- int ret_val = printf_core::printf_main(&writer, format, args);
+ auto ret_val = printf_core::printf_main(&writer, format, args);
+ if (ret_val.has_error()) {
+ libc_errno = ret_val.error;
+ return -1;
+ }
wb.buff[wb.buff_cur] = '\0';
- return ret_val;
+
+ if (ret_val.value > cpp::numeric_limits<int>::max()) {
+ libc_errno = EOVERFLOW;
+ return -1;
+ }
+
+ return static_cast<int>(ret_val.value);
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/vasprintf.cpp b/libc/src/stdio/vasprintf.cpp
index 4a44d4a0f8842..d8ed3a36c7ecf 100644
--- a/libc/src/stdio/vasprintf.cpp
+++ b/libc/src/stdio/vasprintf.cpp
@@ -18,7 +18,16 @@ LLVM_LIBC_FUNCTION(int, vasprintf,
internal::ArgList args(vlist); // This holder class allows for easier copying
// and pointer semantics, as well as handling
// destruction automatically.
- return printf_core::vasprintf_internal(ret, format, args);
+ auto ret_val = printf_core::vasprintf_internal(ret, format, args);
+ if (ret_val.has_error()) {
+ libc_errno = ret_val.error;
+ return -1;
+ }
+ if (ret_val.value > cpp::numeric_limits<int>::max()) {
+ libc_errno = EOVERFLOW;
+ return -1;
+ }
+ return static_cast<int>(ret_val.value);
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/vsnprintf.cpp b/libc/src/stdio/vsnprintf.cpp
index b07a2499a0dd3..f39051cdd4d75 100644
--- a/libc/src/stdio/vsnprintf.cpp
+++ b/libc/src/stdio/vsnprintf.cpp
@@ -29,10 +29,20 @@ LLVM_LIBC_FUNCTION(int, vsnprintf,
wb(buffer, (buffsz > 0 ? buffsz - 1 : 0));
printf_core::Writer writer(wb);
- int ret_val = printf_core::printf_main(&writer, format, args);
+ auto ret_val = printf_core::printf_main(&writer, format, args);
+ if (ret_val.has_error()) {
+ libc_errno = ret_val.error;
+ return -1;
+ }
if (buffsz > 0) // if the buffsz is 0 the buffer may be a null pointer.
wb.buff[wb.buff_cur] = '\0';
- return ret_val;
+
+ if (ret_val.value > cpp::numeric_limits<int>::max()) {
+ libc_errno = EOVERFLOW;
+ return -1;
+ }
+
+ return static_cast<int>(ret_val.value);
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/vsprintf.cpp b/libc/src/stdio/vsprintf.cpp
index 26d497be42125..4c4a3eefaa7b4 100644
--- a/libc/src/stdio/vsprintf.cpp
+++ b/libc/src/stdio/vsprintf.cpp
@@ -30,9 +30,18 @@ LLVM_LIBC_FUNCTION(int, vsprintf,
wb(buffer, cpp::numeric_limits<size_t>::max());
printf_core::Writer writer(wb);
- int ret_val = printf_core::printf_main(&writer, format, args);
+ auto ret_val = printf_core::printf_main(&writer, format, args);
+ if (ret_val.has_error()) {
+ libc_errno = ret_val.error;
+ return -1;
+ }
wb.buff[wb.buff_cur] = '\0';
- return ret_val;
+
+ if (ret_val.value > cpp::numeric_limits<int>::max()) {
+ libc_errno = EOVERFLOW;
+ return -1;
+ }
+ return static_cast<int>(ret_val.value);
}
} // namespace LIBC_NAMESPACE_DECL
>From f8f35538b6dae5d99d58f46e1bc0b7c9055dc916 Mon Sep 17 00:00:00 2001
From: Marcell Leleszi <mleleszi at google.com>
Date: Tue, 7 Oct 2025 07:07:45 +0000
Subject: [PATCH 04/13] Formatting
---
libc/src/stdio/asprintf.cpp | 4 ++--
libc/src/stdio/generic/fprintf.cpp | 4 ++--
libc/src/stdio/generic/printf.cpp | 4 ++--
libc/src/stdio/generic/vfprintf.cpp | 4 ++--
libc/src/stdio/generic/vprintf.cpp | 4 ++--
libc/src/stdio/printf_core/printf_main.h | 4 ++--
libc/src/stdio/printf_core/vasprintf_internal.h | 5 +++--
libc/src/stdio/printf_core/vfprintf_internal.h | 4 ++--
libc/src/stdio/snprintf.cpp | 8 ++++----
libc/src/stdio/sprintf.cpp | 6 +++---
libc/src/stdio/vasprintf.cpp | 2 +-
libc/src/stdio/vsnprintf.cpp | 8 ++++----
libc/src/stdio/vsprintf.cpp | 4 ++--
13 files changed, 31 insertions(+), 30 deletions(-)
diff --git a/libc/src/stdio/asprintf.cpp b/libc/src/stdio/asprintf.cpp
index d392c658b898c..13c1ee68ef0f2 100644
--- a/libc/src/stdio/asprintf.cpp
+++ b/libc/src/stdio/asprintf.cpp
@@ -30,9 +30,9 @@ LLVM_LIBC_FUNCTION(int, asprintf,
if (ret_val.value > cpp::numeric_limits<int>::max()) {
libc_errno = EOVERFLOW;
return -1;
- }
+ }
- return static_cast<int>(ret_val.value);
+ return static_cast<int>(ret_val.value);
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/generic/fprintf.cpp b/libc/src/stdio/generic/fprintf.cpp
index 64d6694770e4e..632264f944f44 100644
--- a/libc/src/stdio/generic/fprintf.cpp
+++ b/libc/src/stdio/generic/fprintf.cpp
@@ -35,9 +35,9 @@ LLVM_LIBC_FUNCTION(int, fprintf,
if (ret_val.value > cpp::numeric_limits<int>::max()) {
libc_errno = EOVERFLOW;
return -1;
- }
+ }
- return static_cast<int>(ret_val.value);
+ return static_cast<int>(ret_val.value);
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/generic/printf.cpp b/libc/src/stdio/generic/printf.cpp
index 0020cce2359e8..482a65cd5a2fa 100644
--- a/libc/src/stdio/generic/printf.cpp
+++ b/libc/src/stdio/generic/printf.cpp
@@ -40,9 +40,9 @@ LLVM_LIBC_FUNCTION(int, printf, (const char *__restrict format, ...)) {
if (ret_val.value > cpp::numeric_limits<int>::max()) {
libc_errno = EOVERFLOW;
return -1;
- }
+ }
- return static_cast<int>(ret_val.value);
+ return static_cast<int>(ret_val.value);
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/generic/vfprintf.cpp b/libc/src/stdio/generic/vfprintf.cpp
index 6311318862bd6..6b39011123084 100644
--- a/libc/src/stdio/generic/vfprintf.cpp
+++ b/libc/src/stdio/generic/vfprintf.cpp
@@ -32,9 +32,9 @@ LLVM_LIBC_FUNCTION(int, vfprintf,
if (ret_val.value > cpp::numeric_limits<int>::max()) {
libc_errno = EOVERFLOW;
return -1;
- }
+ }
- return static_cast<int>(ret_val.value);
+ return static_cast<int>(ret_val.value);
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/generic/vprintf.cpp b/libc/src/stdio/generic/vprintf.cpp
index 73b9701ee2eda..09ba2ce0d32a9 100644
--- a/libc/src/stdio/generic/vprintf.cpp
+++ b/libc/src/stdio/generic/vprintf.cpp
@@ -38,9 +38,9 @@ LLVM_LIBC_FUNCTION(int, vprintf,
if (ret_val.value > cpp::numeric_limits<int>::max()) {
libc_errno = EOVERFLOW;
return -1;
- }
+ }
- return static_cast<int>(ret_val.value);
+ return static_cast<int>(ret_val.value);
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/printf_core/printf_main.h b/libc/src/stdio/printf_core/printf_main.h
index 6a9c9a00265d1..05488ff97f526 100644
--- a/libc/src/stdio/printf_core/printf_main.h
+++ b/libc/src/stdio/printf_core/printf_main.h
@@ -23,7 +23,7 @@ namespace printf_core {
template <WriteMode write_mode>
PrintfResult printf_main(Writer<write_mode> *writer, const char *__restrict str,
- internal::ArgList &args) {
+ internal::ArgList &args) {
Parser<internal::ArgList> parser(str, args);
int result = 0;
for (FormatSection cur_section = parser.get_next_section();
@@ -37,7 +37,7 @@ PrintfResult printf_main(Writer<write_mode> *writer, const char *__restrict str,
if (result < 0)
return {0, -result};
}
-
+
return writer->get_chars_written();
}
diff --git a/libc/src/stdio/printf_core/vasprintf_internal.h b/libc/src/stdio/printf_core/vasprintf_internal.h
index bfc02fedf5244..b96e1afa0b467 100644
--- a/libc/src/stdio/printf_core/vasprintf_internal.h
+++ b/libc/src/stdio/printf_core/vasprintf_internal.h
@@ -43,8 +43,9 @@ LIBC_INLINE int resize_overflow_hook(cpp::string_view new_str, void *target) {
constexpr size_t DEFAULT_BUFFER_SIZE = 200;
-LIBC_INLINE PrintfResult vasprintf_internal(char **ret, const char *__restrict format,
- internal::ArgList args) {
+LIBC_INLINE PrintfResult vasprintf_internal(char **ret,
+ const char *__restrict format,
+ internal::ArgList args) {
char init_buff_on_stack[DEFAULT_BUFFER_SIZE];
printf_core::WriteBuffer<Mode<WriteMode::RESIZE_AND_FILL_BUFF>::value> wb(
init_buff_on_stack, DEFAULT_BUFFER_SIZE, resize_overflow_hook);
diff --git a/libc/src/stdio/printf_core/vfprintf_internal.h b/libc/src/stdio/printf_core/vfprintf_internal.h
index 71a85077e92b8..53a9762606295 100644
--- a/libc/src/stdio/printf_core/vfprintf_internal.h
+++ b/libc/src/stdio/printf_core/vfprintf_internal.h
@@ -69,8 +69,8 @@ LIBC_INLINE int file_write_hook(cpp::string_view new_str, void *fp) {
}
LIBC_INLINE PrintfResult vfprintf_internal(::FILE *__restrict stream,
- const char *__restrict format,
- internal::ArgList &args) {
+ const char *__restrict format,
+ internal::ArgList &args) {
constexpr size_t BUFF_SIZE = 1024;
char buffer[BUFF_SIZE];
printf_core::WriteBuffer<Mode<WriteMode::FLUSH_TO_STREAM>::value> wb(
diff --git a/libc/src/stdio/snprintf.cpp b/libc/src/stdio/snprintf.cpp
index 8c22935b849a0..6691da1debb5a 100644
--- a/libc/src/stdio/snprintf.cpp
+++ b/libc/src/stdio/snprintf.cpp
@@ -39,13 +39,13 @@ LLVM_LIBC_FUNCTION(int, snprintf,
}
if (buffsz > 0) // if the buffsz is 0 the buffer may be a null pointer.
wb.buff[wb.buff_cur] = '\0';
-
+
if (ret_val.value > cpp::numeric_limits<int>::max()) {
libc_errno = EOVERFLOW;
return -1;
- }
-
- return static_cast<int>(ret_val.value);
+ }
+
+ return static_cast<int>(ret_val.value);
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/sprintf.cpp b/libc/src/stdio/sprintf.cpp
index 2557197894bec..10db9feb80121 100644
--- a/libc/src/stdio/sprintf.cpp
+++ b/libc/src/stdio/sprintf.cpp
@@ -43,9 +43,9 @@ LLVM_LIBC_FUNCTION(int, sprintf,
if (ret_val.value > cpp::numeric_limits<int>::max()) {
libc_errno = EOVERFLOW;
return -1;
- }
-
- return static_cast<int>(ret_val.value);
+ }
+
+ return static_cast<int>(ret_val.value);
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/vasprintf.cpp b/libc/src/stdio/vasprintf.cpp
index d8ed3a36c7ecf..11174727e5d64 100644
--- a/libc/src/stdio/vasprintf.cpp
+++ b/libc/src/stdio/vasprintf.cpp
@@ -26,7 +26,7 @@ LLVM_LIBC_FUNCTION(int, vasprintf,
if (ret_val.value > cpp::numeric_limits<int>::max()) {
libc_errno = EOVERFLOW;
return -1;
- }
+ }
return static_cast<int>(ret_val.value);
}
diff --git a/libc/src/stdio/vsnprintf.cpp b/libc/src/stdio/vsnprintf.cpp
index f39051cdd4d75..25e6165897674 100644
--- a/libc/src/stdio/vsnprintf.cpp
+++ b/libc/src/stdio/vsnprintf.cpp
@@ -36,13 +36,13 @@ LLVM_LIBC_FUNCTION(int, vsnprintf,
}
if (buffsz > 0) // if the buffsz is 0 the buffer may be a null pointer.
wb.buff[wb.buff_cur] = '\0';
-
+
if (ret_val.value > cpp::numeric_limits<int>::max()) {
libc_errno = EOVERFLOW;
return -1;
- }
-
- return static_cast<int>(ret_val.value);
+ }
+
+ return static_cast<int>(ret_val.value);
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/vsprintf.cpp b/libc/src/stdio/vsprintf.cpp
index 4c4a3eefaa7b4..6dda2db250d50 100644
--- a/libc/src/stdio/vsprintf.cpp
+++ b/libc/src/stdio/vsprintf.cpp
@@ -40,8 +40,8 @@ LLVM_LIBC_FUNCTION(int, vsprintf,
if (ret_val.value > cpp::numeric_limits<int>::max()) {
libc_errno = EOVERFLOW;
return -1;
- }
- return static_cast<int>(ret_val.value);
+ }
+ return static_cast<int>(ret_val.value);
}
} // namespace LIBC_NAMESPACE_DECL
>From 4761e9a68d279739b4e932331ec3307bdbd4c81f Mon Sep 17 00:00:00 2001
From: Marcell Leleszi <mleleszi at google.com>
Date: Tue, 7 Oct 2025 15:39:17 +0000
Subject: [PATCH 05/13] Fix tests
---
libc/src/stdlib/strfromd.cpp | 2 +-
.../src/stdio/printf_core/converter_test.cpp | 30 ++++++++---------
.../src/stdio/printf_core/writer_test.cpp | 32 +++++++++----------
3 files changed, 32 insertions(+), 32 deletions(-)
diff --git a/libc/src/stdlib/strfromd.cpp b/libc/src/stdlib/strfromd.cpp
index c0989f1a97dca..b35e476086691 100644
--- a/libc/src/stdlib/strfromd.cpp
+++ b/libc/src/stdlib/strfromd.cpp
@@ -28,7 +28,7 @@ LLVM_LIBC_FUNCTION(int, strfromd,
if (section.has_conv)
result = internal::strfromfloat_convert<double>(&writer, section);
else
- result = writer.write(section.raw_string);
+ result = writer.write(section.raw_string); // TODO everywhere where writer is used, set errno and ret -1
if (result < 0)
return result;
diff --git a/libc/test/src/stdio/printf_core/converter_test.cpp b/libc/test/src/stdio/printf_core/converter_test.cpp
index bf088937e4104..2dae2a22c864c 100644
--- a/libc/test/src/stdio/printf_core/converter_test.cpp
+++ b/libc/test/src/stdio/printf_core/converter_test.cpp
@@ -38,7 +38,7 @@ TEST_F(LlvmLibcPrintfConverterTest, SimpleRawConversion) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ(str, "abc");
- ASSERT_EQ(writer.get_chars_written(), 3);
+ ASSERT_EQ(writer.get_chars_written(), size_t{3});
}
TEST_F(LlvmLibcPrintfConverterTest, PercentConversion) {
@@ -52,7 +52,7 @@ TEST_F(LlvmLibcPrintfConverterTest, PercentConversion) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ(str, "%");
- ASSERT_EQ(writer.get_chars_written(), 1);
+ ASSERT_EQ(writer.get_chars_written(), size_t{1});
}
TEST_F(LlvmLibcPrintfConverterTest, CharConversionSimple) {
@@ -70,7 +70,7 @@ TEST_F(LlvmLibcPrintfConverterTest, CharConversionSimple) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ(str, "D");
- ASSERT_EQ(writer.get_chars_written(), 1);
+ ASSERT_EQ(writer.get_chars_written(), size_t{1});
}
TEST_F(LlvmLibcPrintfConverterTest, CharConversionRightJustified) {
@@ -85,7 +85,7 @@ TEST_F(LlvmLibcPrintfConverterTest, CharConversionRightJustified) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ(str, " E");
- ASSERT_EQ(writer.get_chars_written(), 4);
+ ASSERT_EQ(writer.get_chars_written(), size_t{4});
}
TEST_F(LlvmLibcPrintfConverterTest, CharConversionLeftJustified) {
@@ -102,7 +102,7 @@ TEST_F(LlvmLibcPrintfConverterTest, CharConversionLeftJustified) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ(str, "F ");
- ASSERT_EQ(writer.get_chars_written(), 4);
+ ASSERT_EQ(writer.get_chars_written(), size_t{4});
}
TEST_F(LlvmLibcPrintfConverterTest, StringConversionSimple) {
@@ -118,7 +118,7 @@ TEST_F(LlvmLibcPrintfConverterTest, StringConversionSimple) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ(str, "DEF");
- ASSERT_EQ(writer.get_chars_written(), 3);
+ ASSERT_EQ(writer.get_chars_written(), size_t{3});
}
TEST_F(LlvmLibcPrintfConverterTest, StringConversionPrecisionHigh) {
@@ -133,7 +133,7 @@ TEST_F(LlvmLibcPrintfConverterTest, StringConversionPrecisionHigh) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ(str, "456");
- ASSERT_EQ(writer.get_chars_written(), 3);
+ ASSERT_EQ(writer.get_chars_written(), size_t{3});
}
TEST_F(LlvmLibcPrintfConverterTest, StringConversionPrecisionLow) {
@@ -148,7 +148,7 @@ TEST_F(LlvmLibcPrintfConverterTest, StringConversionPrecisionLow) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ(str, "xy");
- ASSERT_EQ(writer.get_chars_written(), 2);
+ ASSERT_EQ(writer.get_chars_written(), size_t{2});
}
TEST_F(LlvmLibcPrintfConverterTest, StringConversionRightJustified) {
@@ -163,7 +163,7 @@ TEST_F(LlvmLibcPrintfConverterTest, StringConversionRightJustified) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ(str, " 789");
- ASSERT_EQ(writer.get_chars_written(), 4);
+ ASSERT_EQ(writer.get_chars_written(), size_t{4});
}
TEST_F(LlvmLibcPrintfConverterTest, StringConversionLeftJustified) {
@@ -180,7 +180,7 @@ TEST_F(LlvmLibcPrintfConverterTest, StringConversionLeftJustified) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ(str, "ghi ");
- ASSERT_EQ(writer.get_chars_written(), 4);
+ ASSERT_EQ(writer.get_chars_written(), size_t{4});
}
TEST_F(LlvmLibcPrintfConverterTest, IntConversionSimple) {
@@ -194,7 +194,7 @@ TEST_F(LlvmLibcPrintfConverterTest, IntConversionSimple) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ(str, "12345");
- ASSERT_EQ(writer.get_chars_written(), 5);
+ ASSERT_EQ(writer.get_chars_written(), size_t{5});
}
TEST_F(LlvmLibcPrintfConverterTest, HexConversion) {
@@ -211,7 +211,7 @@ TEST_F(LlvmLibcPrintfConverterTest, HexConversion) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ(str, "0x00000000123456ab");
- ASSERT_EQ(writer.get_chars_written(), 18);
+ ASSERT_EQ(writer.get_chars_written(), size_t{18});
}
TEST_F(LlvmLibcPrintfConverterTest, BinaryConversion) {
@@ -225,7 +225,7 @@ TEST_F(LlvmLibcPrintfConverterTest, BinaryConversion) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ(str, "101010");
- ASSERT_EQ(writer.get_chars_written(), 6);
+ ASSERT_EQ(writer.get_chars_written(), size_t{6});
}
TEST_F(LlvmLibcPrintfConverterTest, PointerConversion) {
@@ -239,7 +239,7 @@ TEST_F(LlvmLibcPrintfConverterTest, PointerConversion) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ(str, "0x123456ab");
- ASSERT_EQ(writer.get_chars_written(), 10);
+ ASSERT_EQ(writer.get_chars_written(), size_t{10});
}
TEST_F(LlvmLibcPrintfConverterTest, OctConversion) {
@@ -253,5 +253,5 @@ TEST_F(LlvmLibcPrintfConverterTest, OctConversion) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ(str, "1234");
- ASSERT_EQ(writer.get_chars_written(), 4);
+ ASSERT_EQ(writer.get_chars_written(), size_t{4});
}
diff --git a/libc/test/src/stdio/printf_core/writer_test.cpp b/libc/test/src/stdio/printf_core/writer_test.cpp
index d036341be7981..d263cf55aa474 100644
--- a/libc/test/src/stdio/printf_core/writer_test.cpp
+++ b/libc/test/src/stdio/printf_core/writer_test.cpp
@@ -39,7 +39,7 @@ TEST(LlvmLibcPrintfWriterTest, Write) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ("abc", str);
- ASSERT_EQ(writer.get_chars_written(), 3);
+ ASSERT_EQ(writer.get_chars_written(), size_t{3});
}
TEST(LlvmLibcPrintfWriterTest, WriteMultipleTimes) {
@@ -53,7 +53,7 @@ TEST(LlvmLibcPrintfWriterTest, WriteMultipleTimes) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ("abcDEF123", str);
- ASSERT_EQ(writer.get_chars_written(), 9);
+ ASSERT_EQ(writer.get_chars_written(), size_t{9});
}
TEST(LlvmLibcPrintfWriterTest, WriteChars) {
@@ -66,7 +66,7 @@ TEST(LlvmLibcPrintfWriterTest, WriteChars) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ("aaa", str);
- ASSERT_EQ(writer.get_chars_written(), 3);
+ ASSERT_EQ(writer.get_chars_written(), size_t{3});
}
TEST(LlvmLibcPrintfWriterTest, WriteCharsMultipleTimes) {
@@ -80,7 +80,7 @@ TEST(LlvmLibcPrintfWriterTest, WriteCharsMultipleTimes) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ("aaaDDD111", str);
- ASSERT_EQ(writer.get_chars_written(), 9);
+ ASSERT_EQ(writer.get_chars_written(), size_t{9});
}
TEST(LlvmLibcPrintfWriterTest, WriteManyChars) {
@@ -102,7 +102,7 @@ TEST(LlvmLibcPrintfWriterTest, WriteManyChars) {
"ZZZZZZZZZZ"
"ZZZZZZZZZ",
str);
- ASSERT_EQ(writer.get_chars_written(), 99);
+ ASSERT_EQ(writer.get_chars_written(), size_t{99});
}
TEST(LlvmLibcPrintfWriterTest, MixedWrites) {
@@ -117,7 +117,7 @@ TEST(LlvmLibcPrintfWriterTest, MixedWrites) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ("aaaDEF111456", str);
- ASSERT_EQ(writer.get_chars_written(), 12);
+ ASSERT_EQ(writer.get_chars_written(), size_t{12});
}
TEST(LlvmLibcPrintfWriterTest, WriteWithMaxLength) {
@@ -129,7 +129,7 @@ TEST(LlvmLibcPrintfWriterTest, WriteWithMaxLength) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ("abcDEF1234", str);
- ASSERT_EQ(writer.get_chars_written(), 12);
+ ASSERT_EQ(writer.get_chars_written(), size_t{12});
}
TEST(LlvmLibcPrintfWriterTest, WriteCharsWithMaxLength) {
@@ -141,7 +141,7 @@ TEST(LlvmLibcPrintfWriterTest, WriteCharsWithMaxLength) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ("1111111111", str);
- ASSERT_EQ(writer.get_chars_written(), 15);
+ ASSERT_EQ(writer.get_chars_written(), size_t{15});
}
TEST(LlvmLibcPrintfWriterTest, MixedWriteWithMaxLength) {
@@ -157,7 +157,7 @@ TEST(LlvmLibcPrintfWriterTest, MixedWriteWithMaxLength) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ("aaaDEF1114", str);
- ASSERT_EQ(writer.get_chars_written(), 12);
+ ASSERT_EQ(writer.get_chars_written(), size_t{12});
}
TEST(LlvmLibcPrintfWriterTest, StringWithMaxLengthOne) {
@@ -175,7 +175,7 @@ TEST(LlvmLibcPrintfWriterTest, StringWithMaxLengthOne) {
wb.buff[wb.buff_cur] = '\0';
ASSERT_STREQ("", str);
- ASSERT_EQ(writer.get_chars_written(), 12);
+ ASSERT_EQ(writer.get_chars_written(), size_t{12});
}
TEST(LlvmLibcPrintfWriterTest, NullStringWithZeroMaxLength) {
@@ -187,7 +187,7 @@ TEST(LlvmLibcPrintfWriterTest, NullStringWithZeroMaxLength) {
writer.write('1', 3);
writer.write({"456", 3});
- ASSERT_EQ(writer.get_chars_written(), 12);
+ ASSERT_EQ(writer.get_chars_written(), size_t{12});
}
struct OutBuff {
@@ -226,7 +226,7 @@ TEST(LlvmLibcPrintfWriterTest, WriteWithMaxLengthWithCallback) {
str[out_buff.cur_pos] = '\0';
ASSERT_STREQ("abcDEF123456", str);
- ASSERT_EQ(writer.get_chars_written(), 12);
+ ASSERT_EQ(writer.get_chars_written(), size_t{12});
}
TEST(LlvmLibcPrintfWriterTest, WriteCharsWithMaxLengthWithCallback) {
@@ -246,7 +246,7 @@ TEST(LlvmLibcPrintfWriterTest, WriteCharsWithMaxLengthWithCallback) {
str[out_buff.cur_pos] = '\0';
ASSERT_STREQ("111111111111111", str);
- ASSERT_EQ(writer.get_chars_written(), 15);
+ ASSERT_EQ(writer.get_chars_written(), size_t{15});
}
TEST(LlvmLibcPrintfWriterTest, MixedWriteWithMaxLengthWithCallback) {
@@ -269,7 +269,7 @@ TEST(LlvmLibcPrintfWriterTest, MixedWriteWithMaxLengthWithCallback) {
str[out_buff.cur_pos] = '\0';
ASSERT_STREQ("aaaDEF111456", str);
- ASSERT_EQ(writer.get_chars_written(), 12);
+ ASSERT_EQ(writer.get_chars_written(), size_t{12});
}
TEST(LlvmLibcPrintfWriterTest, ZeroLengthBufferWithCallback) {
@@ -292,7 +292,7 @@ TEST(LlvmLibcPrintfWriterTest, ZeroLengthBufferWithCallback) {
str[out_buff.cur_pos] = '\0';
ASSERT_STREQ("aaaDEF111456", str);
- ASSERT_EQ(writer.get_chars_written(), 12);
+ ASSERT_EQ(writer.get_chars_written(), size_t{12});
}
TEST(LlvmLibcPrintfWriterTest, NullStringWithZeroMaxLengthWithCallback) {
@@ -312,7 +312,7 @@ TEST(LlvmLibcPrintfWriterTest, NullStringWithZeroMaxLengthWithCallback) {
wb.overflow_write("");
str[out_buff.cur_pos] = '\0';
- ASSERT_EQ(writer.get_chars_written(), 12);
+ ASSERT_EQ(writer.get_chars_written(), size_t{12});
ASSERT_STREQ("aaaDEF111456", str);
}
>From 1dd65af1dae8b5a55305b1881f3dbc30163c0724 Mon Sep 17 00:00:00 2001
From: Marcell Leleszi <mleleszi at google.com>
Date: Tue, 7 Oct 2025 16:28:29 +0000
Subject: [PATCH 06/13] Add IO error test cases for file variants
---
libc/src/stdio/printf_core/vasprintf_internal.h | 4 ++--
libc/test/src/stdio/CMakeLists.txt | 2 ++
libc/test/src/stdio/fprintf_test.cpp | 5 +++++
libc/test/src/stdio/vfprintf_test.cpp | 5 +++++
4 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/libc/src/stdio/printf_core/vasprintf_internal.h b/libc/src/stdio/printf_core/vasprintf_internal.h
index b96e1afa0b467..f84f60bec2fc6 100644
--- a/libc/src/stdio/printf_core/vasprintf_internal.h
+++ b/libc/src/stdio/printf_core/vasprintf_internal.h
@@ -59,12 +59,12 @@ LIBC_INLINE PrintfResult vasprintf_internal(char **ret,
if (wb.buff == init_buff_on_stack) {
*ret = static_cast<char *>(malloc(ret_val.value + 1));
if (ret == nullptr)
- return -ENOMEM;
+ return {0, ENOMEM};
inline_memcpy(*ret, wb.buff, ret_val.value);
} else {
*ret = wb.buff;
}
- (*ret)[ret_val.value] = '\0'; // TODO OK HERE or overflow
+ (*ret)[ret_val.value] = '\0';
return ret_val;
}
} // namespace printf_core
diff --git a/libc/test/src/stdio/CMakeLists.txt b/libc/test/src/stdio/CMakeLists.txt
index eec108bc12ca5..d71f1dff11943 100644
--- a/libc/test/src/stdio/CMakeLists.txt
+++ b/libc/test/src/stdio/CMakeLists.txt
@@ -186,6 +186,8 @@ add_libc_test(
fprintf_test.cpp
DEPENDS
libc.src.stdio.fprintf
+ libc.test.UnitTest.ErrnoCheckingTest
+ libc.test.UnitTest.ErrnoSetterMatcher
${fprintf_test_deps}
COMPILE_OPTIONS
${use_system_file}
diff --git a/libc/test/src/stdio/fprintf_test.cpp b/libc/test/src/stdio/fprintf_test.cpp
index 6799323cc6ad9..3a764e102dc71 100644
--- a/libc/test/src/stdio/fprintf_test.cpp
+++ b/libc/test/src/stdio/fprintf_test.cpp
@@ -16,6 +16,8 @@
#include "src/stdio/fprintf.h"
#include "test/UnitTest/Test.h"
+#include "test/UnitTest/ErrnoCheckingTest.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
namespace printf_test {
#ifndef LIBC_COPT_STDIO_USE_SYSTEM_FILE
@@ -31,6 +33,8 @@ using ::fread;
#endif // LIBC_COPT_STDIO_USE_SYSTEM_FILE
} // namespace printf_test
+using LlvmLibcFPrintfTest = LIBC_NAMESPACE::testing::ErrnoCheckingTest;
+
TEST(LlvmLibcFPrintfTest, WriteToFile) {
const char *FILENAME = APPEND_LIBC_TEST("fprintf_output.test");
auto FILE_PATH = libc_make_test_file_path(FILENAME);
@@ -78,6 +82,7 @@ TEST(LlvmLibcFPrintfTest, WriteToFile) {
written =
LIBC_NAMESPACE::fprintf(file, "Writing to a read only file should fail.");
EXPECT_LT(written, 0);
+ ASSERT_ERRNO_EQ(EIO);
ASSERT_EQ(printf_test::fclose(file), 0);
}
diff --git a/libc/test/src/stdio/vfprintf_test.cpp b/libc/test/src/stdio/vfprintf_test.cpp
index f50565a0f68ca..43240ce13cc96 100644
--- a/libc/test/src/stdio/vfprintf_test.cpp
+++ b/libc/test/src/stdio/vfprintf_test.cpp
@@ -20,6 +20,8 @@
#include "src/stdio/vfprintf.h"
#include "test/UnitTest/Test.h"
+#include "test/UnitTest/ErrnoCheckingTest.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
namespace printf_test {
#ifndef LIBC_COPT_STDIO_USE_SYSTEM_FILE
@@ -44,6 +46,8 @@ int call_vfprintf(::FILE *__restrict stream, const char *__restrict format,
return ret;
}
+using LlvmLibcVFPrintfTest = LIBC_NAMESPACE::testing::ErrnoCheckingTest;
+
TEST(LlvmLibcVFPrintfTest, WriteToFile) {
const char *FILENAME = APPEND_LIBC_TEST("vfprintf_output.test");
auto FILE_PATH = libc_make_test_file_path(FILENAME);
@@ -90,6 +94,7 @@ TEST(LlvmLibcVFPrintfTest, WriteToFile) {
written = call_vfprintf(file, "Writing to a read only file should fail.");
EXPECT_LT(written, 0);
+ ASSERT_ERRNO_EQ(EIO);
ASSERT_EQ(printf_test::fclose(file), 0);
}
>From ef55545a80b33bbd2947514f4a081b993b389c0e Mon Sep 17 00:00:00 2001
From: Marcell Leleszi <mleleszi at google.com>
Date: Tue, 7 Oct 2025 17:17:50 +0000
Subject: [PATCH 07/13] Add overflow test for fprintf
---
libc/test/src/stdio/CMakeLists.txt | 1 +
libc/test/src/stdio/fprintf_test.cpp | 28 +++++++++++++++++++++++++++-
2 files changed, 28 insertions(+), 1 deletion(-)
diff --git a/libc/test/src/stdio/CMakeLists.txt b/libc/test/src/stdio/CMakeLists.txt
index d71f1dff11943..b513007cdf7c6 100644
--- a/libc/test/src/stdio/CMakeLists.txt
+++ b/libc/test/src/stdio/CMakeLists.txt
@@ -169,6 +169,7 @@ if(LLVM_LIBC_FULL_BUILD)
libc.src.stdio.ferror
libc.src.stdio.fopen
libc.src.stdio.fread
+ libc.src.stdio.fopencookie
)
# This is to be used for tests which write to libc's platform streams
# under full build but write to system-lib's streams otherwise.
diff --git a/libc/test/src/stdio/fprintf_test.cpp b/libc/test/src/stdio/fprintf_test.cpp
index 3a764e102dc71..6d52611ae98b1 100644
--- a/libc/test/src/stdio/fprintf_test.cpp
+++ b/libc/test/src/stdio/fprintf_test.cpp
@@ -10,25 +10,29 @@
#include "src/stdio/fclose.h"
#include "src/stdio/ferror.h"
#include "src/stdio/fopen.h"
+#include "src/stdio/fopencookie.h"
#include "src/stdio/fread.h"
#endif // LIBC_COPT_STDIO_USE_SYSTEM_FILE
#include "src/stdio/fprintf.h"
-#include "test/UnitTest/Test.h"
+#include "src/__support/CPP/limits.h"
#include "test/UnitTest/ErrnoCheckingTest.h"
#include "test/UnitTest/ErrnoSetterMatcher.h"
+#include "test/UnitTest/Test.h"
namespace printf_test {
#ifndef LIBC_COPT_STDIO_USE_SYSTEM_FILE
using LIBC_NAMESPACE::fclose;
using LIBC_NAMESPACE::ferror;
using LIBC_NAMESPACE::fopen;
+using LIBC_NAMESPACE::fopencookie;
using LIBC_NAMESPACE::fread;
#else // defined(LIBC_COPT_STDIO_USE_SYSTEM_FILE)
using ::fclose;
using ::ferror;
using ::fopen;
+using ::fopencookie;
using ::fread;
#endif // LIBC_COPT_STDIO_USE_SYSTEM_FILE
} // namespace printf_test
@@ -86,3 +90,25 @@ TEST(LlvmLibcFPrintfTest, WriteToFile) {
ASSERT_EQ(printf_test::fclose(file), 0);
}
+
+struct NoopStream {};
+
+static ssize_t noop_write(void *, const char *, size_t size) { return size; }
+
+TEST(LlvmLibcFPrintfTest, CharsWrittenOverflow) {
+ NoopStream stream;
+ cookie_io_functions_t funcs = {nullptr, &noop_write, nullptr, nullptr};
+ ::FILE *file = printf_test::fopencookie(&stream, "w", funcs);
+ ASSERT_NE(file, nullptr);
+
+ // Trigger an overflow in the return value of fprintf by writing more than
+ // INT_MAX bytes. We do this by printing a string with precision INT_MAX, and
+ // then one more character.
+ int max_int = LIBC_NAMESPACE::cpp::numeric_limits<int>::max();
+ int result = LIBC_NAMESPACE::fprintf(file, "%*sA", max_int, "");
+
+ EXPECT_LT(result, 0);
+ ASSERT_ERRNO_EQ(EOVERFLOW);
+
+ EXPECT_EQ(printf_test::fclose(file), 0);
+}
\ No newline at end of file
>From 63c710b793e4bcfe1b6401aeb5c0843e45ae9150 Mon Sep 17 00:00:00 2001
From: Marcell Leleszi <mleleszi at google.com>
Date: Tue, 7 Oct 2025 18:19:56 +0000
Subject: [PATCH 08/13] Cleanup
---
libc/src/stdio/baremetal/printf.cpp | 2 +-
libc/src/stdio/baremetal/vprintf.cpp | 4 ++--
libc/src/stdio/printf_core/core_structs.h | 2 +-
libc/src/stdio/printf_core/printf_main.h | 4 ++--
libc/src/time/strftime_core/strftime_main.h | 2 +-
libc/test/src/stdio/fprintf_test.cpp | 11 ++++++-----
6 files changed, 13 insertions(+), 12 deletions(-)
diff --git a/libc/src/stdio/baremetal/printf.cpp b/libc/src/stdio/baremetal/printf.cpp
index 7253c6549a4e4..6f4ebb35d4004 100644
--- a/libc/src/stdio/baremetal/printf.cpp
+++ b/libc/src/stdio/baremetal/printf.cpp
@@ -47,7 +47,7 @@ LLVM_LIBC_FUNCTION(int, printf, (const char *__restrict format, ...)) {
int flushval = wb.overflow_write("");
if (flushval != printf_core::WRITE_OK)
retval = flushval;
-
+
return retval;
}
diff --git a/libc/src/stdio/baremetal/vprintf.cpp b/libc/src/stdio/baremetal/vprintf.cpp
index ab02533f14911..4401ddbe8690e 100644
--- a/libc/src/stdio/baremetal/vprintf.cpp
+++ b/libc/src/stdio/baremetal/vprintf.cpp
@@ -22,7 +22,7 @@ namespace LIBC_NAMESPACE_DECL {
namespace {
LIBC_INLINE int stdout_write_hook(cpp::string_view new_str, void *) {
- write_to_stdout(new_str);
+ write_to_stdout(new_str);
return printf_core::WRITE_OK;
}
@@ -40,7 +40,7 @@ LLVM_LIBC_FUNCTION(int, vprintf,
buffer, BUFF_SIZE, &stdout_write_hook, nullptr);
printf_core::Writer<printf_core::WriteMode::FLUSH_TO_STREAM> writer(wb);
- int retval = printf_core::printf_main(&writer, format, args);
+ int retval = printf_core::printf_main(&writer, format, args); // TODO baremetal stuff
int flushval = wb.overflow_write("");
if (flushval != printf_core::WRITE_OK)
diff --git a/libc/src/stdio/printf_core/core_structs.h b/libc/src/stdio/printf_core/core_structs.h
index e397e4a5b3abe..22b674da789a5 100644
--- a/libc/src/stdio/printf_core/core_structs.h
+++ b/libc/src/stdio/printf_core/core_structs.h
@@ -31,7 +31,7 @@ struct PrintfResult {
constexpr bool has_error() { return error != 0; }
- constexpr operator size_t() { return value; }
+ // constexpr operator size_t() { return value; }
};
// These length modifiers match the length modifiers in the format string, which
diff --git a/libc/src/stdio/printf_core/printf_main.h b/libc/src/stdio/printf_core/printf_main.h
index 05488ff97f526..7bb5b3f3d1cf5 100644
--- a/libc/src/stdio/printf_core/printf_main.h
+++ b/libc/src/stdio/printf_core/printf_main.h
@@ -30,9 +30,9 @@ PrintfResult printf_main(Writer<write_mode> *writer, const char *__restrict str,
!cur_section.raw_string.empty();
cur_section = parser.get_next_section()) {
if (cur_section.has_conv)
- result = convert(writer, cur_section);
+ result = convert(writer, cur_section); // look at usages
else
- result = writer->write(cur_section.raw_string);
+ result = writer->write(cur_section.raw_string); // look at usages
if (result < 0)
return {0, -result};
diff --git a/libc/src/time/strftime_core/strftime_main.h b/libc/src/time/strftime_core/strftime_main.h
index c7e590627094a..a97e00dfd9b64 100644
--- a/libc/src/time/strftime_core/strftime_main.h
+++ b/libc/src/time/strftime_core/strftime_main.h
@@ -36,7 +36,7 @@ int strftime_main(printf_core::Writer<write_mode> *writer,
return result;
}
- return writer->get_chars_written();
+ return static_cast<int>(writer->get_chars_written());
}
} // namespace strftime_core
diff --git a/libc/test/src/stdio/fprintf_test.cpp b/libc/test/src/stdio/fprintf_test.cpp
index 6d52611ae98b1..53d056da1f36d 100644
--- a/libc/test/src/stdio/fprintf_test.cpp
+++ b/libc/test/src/stdio/fprintf_test.cpp
@@ -91,13 +91,14 @@ TEST(LlvmLibcFPrintfTest, WriteToFile) {
ASSERT_EQ(printf_test::fclose(file), 0);
}
-struct NoopStream {};
-
-static ssize_t noop_write(void *, const char *, size_t size) { return size; }
-
TEST(LlvmLibcFPrintfTest, CharsWrittenOverflow) {
+ struct NoopStream {};
+ auto noop_write = [](void *cookie, const char *buf, size_t size) -> ssize_t {
+ return size;
+ };
+
NoopStream stream;
- cookie_io_functions_t funcs = {nullptr, &noop_write, nullptr, nullptr};
+ cookie_io_functions_t funcs = {nullptr, +noop_write, nullptr, nullptr};
::FILE *file = printf_test::fopencookie(&stream, "w", funcs);
ASSERT_NE(file, nullptr);
>From e035a15cb26c61de8ee052a8e8758856a4ebb56d Mon Sep 17 00:00:00 2001
From: Marcell Leleszi <mleleszi at google.com>
Date: Wed, 8 Oct 2025 16:03:09 +0000
Subject: [PATCH 09/13] Add overflow test for vfprintf
---
libc/test/src/stdio/vfprintf_test.cpp | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/libc/test/src/stdio/vfprintf_test.cpp b/libc/test/src/stdio/vfprintf_test.cpp
index 43240ce13cc96..6664d500f2816 100644
--- a/libc/test/src/stdio/vfprintf_test.cpp
+++ b/libc/test/src/stdio/vfprintf_test.cpp
@@ -15,6 +15,7 @@
#include "src/stdio/ferror.h"
#include "src/stdio/fopen.h"
#include "src/stdio/fread.h"
+#include "src/stdio/fopencookie.h"
#endif // LIBC_COPT_STDIO_USE_SYSTEM_FILE
#include "src/stdio/vfprintf.h"
@@ -29,11 +30,13 @@ using LIBC_NAMESPACE::fclose;
using LIBC_NAMESPACE::ferror;
using LIBC_NAMESPACE::fopen;
using LIBC_NAMESPACE::fread;
+using LIBC_NAMESPACE::fopencookie;
#else // defined(LIBC_COPT_STDIO_USE_SYSTEM_FILE)
using ::fclose;
using ::ferror;
using ::fopen;
using ::fread;
+using ::fopencookie;
#endif // LIBC_COPT_STDIO_USE_SYSTEM_FILE
} // namespace printf_test
@@ -98,3 +101,26 @@ TEST(LlvmLibcVFPrintfTest, WriteToFile) {
ASSERT_EQ(printf_test::fclose(file), 0);
}
+
+TEST(LlvmLibcVFPrintfTest, CharsWrittenOverflow) {
+ struct NoopStream {};
+ auto noop_write = [](void *cookie, const char *buf, size_t size) -> ssize_t {
+ return size;
+ };
+
+ NoopStream stream;
+ cookie_io_functions_t funcs = {nullptr, +noop_write, nullptr, nullptr};
+ ::FILE *file = printf_test::fopencookie(&stream, "w", funcs);
+ ASSERT_NE(file, nullptr);
+
+ // Trigger an overflow in the return value of vfprintf by writing more than
+ // INT_MAX bytes. We do this by printing a string with precision INT_MAX, and
+ // then one more character.
+ int max_int = LIBC_NAMESPACE::cpp::numeric_limits<int>::max();
+ int result = call_vfprintf(file, "%*sA", max_int, "");
+
+ EXPECT_LT(result, 0);
+ ASSERT_ERRNO_EQ(EOVERFLOW);
+
+ EXPECT_EQ(printf_test::fclose(file), 0);
+}
>From 56d69681324d3d49f1c156ed8341b3a68e447b1e Mon Sep 17 00:00:00 2001
From: Marcell Leleszi <mleleszi at google.com>
Date: Wed, 8 Oct 2025 16:25:14 +0000
Subject: [PATCH 10/13] Baremetal stuff
---
libc/src/stdio/baremetal/printf.cpp | 21 ++++++++++++++-----
libc/src/stdio/baremetal/vprintf.cpp | 20 ++++++++++++++----
.../src/stdio/printf_core/vfprintf_internal.h | 4 ++++
3 files changed, 36 insertions(+), 9 deletions(-)
diff --git a/libc/src/stdio/baremetal/printf.cpp b/libc/src/stdio/baremetal/printf.cpp
index 6f4ebb35d4004..58ff12ba125ea 100644
--- a/libc/src/stdio/baremetal/printf.cpp
+++ b/libc/src/stdio/baremetal/printf.cpp
@@ -42,13 +42,24 @@ LLVM_LIBC_FUNCTION(int, printf, (const char *__restrict format, ...)) {
buffer, BUFF_SIZE, &stdout_write_hook, nullptr);
printf_core::Writer<printf_core::WriteMode::FLUSH_TO_STREAM> writer(wb);
- int retval = printf_core::printf_main(&writer, format, args);
+ auto retval = printf_core::printf_main(&writer, format, args);
+ if (retval.has_error()) {
+ libc_errno = retval.error;
+ return -1;
+ }
int flushval = wb.overflow_write("");
- if (flushval != printf_core::WRITE_OK)
- retval = flushval;
-
- return retval;
+ if (flushval != printf_core::WRITE_OK) {
+ libc_errno = -flushval;
+ return -1;
+ }
+
+ if (retval.value >= cpp::numeric_limits<int>::max()) {
+ libc_errno = EOVERFLOW;
+ return -1;
+ }
+
+ return static_cast<int>(retval.value);
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/baremetal/vprintf.cpp b/libc/src/stdio/baremetal/vprintf.cpp
index 4401ddbe8690e..7dcf01280685f 100644
--- a/libc/src/stdio/baremetal/vprintf.cpp
+++ b/libc/src/stdio/baremetal/vprintf.cpp
@@ -40,13 +40,25 @@ LLVM_LIBC_FUNCTION(int, vprintf,
buffer, BUFF_SIZE, &stdout_write_hook, nullptr);
printf_core::Writer<printf_core::WriteMode::FLUSH_TO_STREAM> writer(wb);
- int retval = printf_core::printf_main(&writer, format, args); // TODO baremetal stuff
+ auto retval = printf_core::printf_main(&writer, format, args);
+ if (retval.has_error()) {
+ libc_errno = retval.error;
+ return -1;
+ }
int flushval = wb.overflow_write("");
- if (flushval != printf_core::WRITE_OK)
- retval = flushval;
+ if (flushval != printf_core::WRITE_OK) {
+ libc_errno = -flushval;
+ return -1;
+
+ }
- return retval;
+ if (retval.value >= cpp::numeric_limits<int>::max()) {
+ libc_errno = EOVERFLOW;
+ return -1;
+ }
+
+ return static_cast<int>(retval.value);
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/printf_core/vfprintf_internal.h b/libc/src/stdio/printf_core/vfprintf_internal.h
index 53a9762606295..c50cacf2709a7 100644
--- a/libc/src/stdio/printf_core/vfprintf_internal.h
+++ b/libc/src/stdio/printf_core/vfprintf_internal.h
@@ -78,6 +78,10 @@ LIBC_INLINE PrintfResult vfprintf_internal(::FILE *__restrict stream,
Writer writer(wb);
internal::flockfile(stream);
auto retval = printf_main(&writer, format, args);
+ if (retval.has_error()) {
+ internal::funlockfile(stream);
+ return retval;
+ }
int flushval = wb.overflow_write("");
if (flushval != WRITE_OK)
retval.error = -flushval;
>From 995bb08795001429bdd18f784ca005684805a076 Mon Sep 17 00:00:00 2001
From: Marcell Leleszi <mleleszi at google.com>
Date: Wed, 8 Oct 2025 16:42:05 +0000
Subject: [PATCH 11/13] Add test for nullptr write error
---
libc/src/stdio/printf_core/core_structs.h | 8 --------
libc/test/src/stdio/fprintf_test.cpp | 18 +++++++++++++++++-
2 files changed, 17 insertions(+), 9 deletions(-)
diff --git a/libc/src/stdio/printf_core/core_structs.h b/libc/src/stdio/printf_core/core_structs.h
index 22b674da789a5..ab6c9228fd76f 100644
--- a/libc/src/stdio/printf_core/core_structs.h
+++ b/libc/src/stdio/printf_core/core_structs.h
@@ -144,14 +144,6 @@ template <typename T> LIBC_INLINE constexpr TypeDesc type_desc_from_type() {
// This is the value to be returned by conversions when no error has occurred.
constexpr int WRITE_OK = 0;
-// These are the printf return values for when an error has occurred. They are
-// all negative, and should be distinct.
-// constexpr int FILE_WRITE_ERROR = -1;
-// constexpr int FILE_STATUS_ERROR = -2;
-// constexpr int NULLPTR_WRITE_ERROR = -3;
-// constexpr int INT_CONVERSION_ERROR = -4;
-// constexpr int FIXED_POINT_CONVERSION_ERROR = -5;
-// constexpr int ALLOCATION_ERROR = -6;
} // namespace printf_core
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/test/src/stdio/fprintf_test.cpp b/libc/test/src/stdio/fprintf_test.cpp
index 53d056da1f36d..f80077fd0885d 100644
--- a/libc/test/src/stdio/fprintf_test.cpp
+++ b/libc/test/src/stdio/fprintf_test.cpp
@@ -112,4 +112,20 @@ TEST(LlvmLibcFPrintfTest, CharsWrittenOverflow) {
ASSERT_ERRNO_EQ(EOVERFLOW);
EXPECT_EQ(printf_test::fclose(file), 0);
-}
\ No newline at end of file
+}
+
+#ifndef LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
+TEST(LlvmLibcFPrintfTest, NullPtrCheck) {
+ const char *FILENAME = APPEND_LIBC_TEST("fprintf_nullptr.test");
+ auto FILE_PATH = libc_make_test_file_path(FILENAME);
+
+ ::FILE *file = printf_test::fopen(FILE_PATH, "w");
+ ASSERT_FALSE(file == nullptr);
+
+ int ret = LIBC_NAMESPACE::fprintf(file, "hello %n", (int *)nullptr);
+ EXPECT_LT(ret, 0);
+ ASSERT_ERRNO_EQ(EINVAL);
+
+ ASSERT_EQ(printf_test::fclose(file), 0);
+}
+#endif // LIBC_COPT_PRINTF_NO_NULLPTR_CHECKS
>From eedbad9782d5f9368334be8064e3a1d34847686b Mon Sep 17 00:00:00 2001
From: Marcell Leleszi <mleleszi at google.com>
Date: Wed, 8 Oct 2025 18:44:12 +0000
Subject: [PATCH 12/13] Add overflow handling to strfrom functions
---
libc/src/stdlib/strfromd.cpp | 5 ++++-
libc/src/stdlib/strfromf.cpp | 5 ++++-
libc/src/stdlib/strfroml.cpp | 5 ++++-
libc/src/time/strftime_core/strftime_main.h | 1 +
libc/test/src/stdlib/StrfromTest.h | 20 ++++++++++++++++++--
5 files changed, 31 insertions(+), 5 deletions(-)
diff --git a/libc/src/stdlib/strfromd.cpp b/libc/src/stdlib/strfromd.cpp
index b35e476086691..2ef8d7e7bdd64 100644
--- a/libc/src/stdlib/strfromd.cpp
+++ b/libc/src/stdlib/strfromd.cpp
@@ -36,7 +36,10 @@ LLVM_LIBC_FUNCTION(int, strfromd,
if (n > 0)
wb.buff[wb.buff_cur] = '\0';
- // TODO overflow
+ if (writer.get_chars_written() > cpp::numeric_limits<int>::max()) {
+ libc_errno = EOVERFLOW;
+ return -1;
+ }
return static_cast<int>(writer.get_chars_written());
}
diff --git a/libc/src/stdlib/strfromf.cpp b/libc/src/stdlib/strfromf.cpp
index 01090c997af1b..5c3e95f4146f2 100644
--- a/libc/src/stdlib/strfromf.cpp
+++ b/libc/src/stdlib/strfromf.cpp
@@ -36,7 +36,10 @@ LLVM_LIBC_FUNCTION(int, strfromf,
if (n > 0)
wb.buff[wb.buff_cur] = '\0';
- // TODO overflow
+ if (writer.get_chars_written() > cpp::numeric_limits<int>::max()) {
+ libc_errno = EOVERFLOW;
+ return -1;
+ }
return static_cast<int>(writer.get_chars_written());
}
diff --git a/libc/src/stdlib/strfroml.cpp b/libc/src/stdlib/strfroml.cpp
index 436243d1e1c38..1605e8ab7c18f 100644
--- a/libc/src/stdlib/strfroml.cpp
+++ b/libc/src/stdlib/strfroml.cpp
@@ -41,7 +41,10 @@ LLVM_LIBC_FUNCTION(int, strfroml,
if (n > 0)
wb.buff[wb.buff_cur] = '\0';
- // TODO overflow
+ if (writer.get_chars_written() > cpp::numeric_limits<int>::max()) {
+ libc_errno = EOVERFLOW;
+ return -1;
+ }
return static_cast<int>(writer.get_chars_written());
}
diff --git a/libc/src/time/strftime_core/strftime_main.h b/libc/src/time/strftime_core/strftime_main.h
index a97e00dfd9b64..865433b8b54c9 100644
--- a/libc/src/time/strftime_core/strftime_main.h
+++ b/libc/src/time/strftime_core/strftime_main.h
@@ -36,6 +36,7 @@ int strftime_main(printf_core::Writer<write_mode> *writer,
return result;
}
+ // TODO could work similar to printf, retval is size_t in libc outer func
return static_cast<int>(writer->get_chars_written());
}
diff --git a/libc/test/src/stdlib/StrfromTest.h b/libc/test/src/stdlib/StrfromTest.h
index e82c94499aa11..f24178b2366c9 100644
--- a/libc/test/src/stdlib/StrfromTest.h
+++ b/libc/test/src/stdlib/StrfromTest.h
@@ -6,16 +6,19 @@
//
//===----------------------------------------------------------------------===//
+#include "src/__support/CPP/limits.h"
#include "src/__support/CPP/type_traits.h"
#include "src/__support/FPUtil/FPBits.h"
#include "test/UnitTest/Test.h"
+#include "test/UnitTest/ErrnoCheckingTest.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
#define ASSERT_STREQ_LEN(actual_written, actual_str, expected_str) \
EXPECT_EQ(actual_written, static_cast<int>(sizeof(expected_str) - 1)); \
EXPECT_STREQ(actual_str, expected_str);
template <typename InputT>
-class StrfromTest : public LIBC_NAMESPACE::testing::Test {
+class StrfromTest : public LIBC_NAMESPACE::testing::ErrnoCheckingTest {
static constexpr bool is_single_prec =
LIBC_NAMESPACE::cpp::is_same<InputT, float>::value;
@@ -481,6 +484,16 @@ class StrfromTest : public LIBC_NAMESPACE::testing::Test {
written = func(buff, 10, "%A", -ld_nan);
ASSERT_STREQ_LEN(written, buff, "-NAN");
}
+
+ void charsWrittenOverflow(FunctionT func) {
+ char buff[100];
+ // Trigger an overflow in the return value of strfrom by writing more than
+ // INT_MAX bytes.
+ int result = func(buff, sizeof(buff), "%.2147483647f", 1.0f);
+
+ EXPECT_LT(result, 0);
+ ASSERT_ERRNO_EQ(EOVERFLOW);
+ }
};
#define STRFROM_TEST(InputType, name, func) \
@@ -501,4 +514,7 @@ class StrfromTest : public LIBC_NAMESPACE::testing::Test {
TEST_F(LlvmLibc##name##Test, InsufficientBufferSize) { \
insufficentBufsize(func); \
} \
- TEST_F(LlvmLibc##name##Test, InfAndNanValues) { infNanValues(func); }
+ TEST_F(LlvmLibc##name##Test, InfAndNanValues) { infNanValues(func); } \
+ TEST_F(LlvmLibc##name##Test, CharsWrittenOverflow) { \
+ charsWrittenOverflow(func); \
+ }
>From 242b75ced96c1263654e4261509aadc6f6c340be Mon Sep 17 00:00:00 2001
From: Marcell Leleszi <mleleszi at google.com>
Date: Fri, 10 Oct 2025 16:00:28 +0000
Subject: [PATCH 13/13] Cleanup
---
libc/src/stdio/baremetal/printf.cpp | 2 +-
libc/src/stdio/baremetal/vprintf.cpp | 4 ++--
libc/src/stdio/printf_core/core_structs.h | 2 +-
libc/src/stdio/printf_core/printf_main.h | 5 ++---
4 files changed, 6 insertions(+), 7 deletions(-)
diff --git a/libc/src/stdio/baremetal/printf.cpp b/libc/src/stdio/baremetal/printf.cpp
index 58ff12ba125ea..e100f946ae9d7 100644
--- a/libc/src/stdio/baremetal/printf.cpp
+++ b/libc/src/stdio/baremetal/printf.cpp
@@ -54,7 +54,7 @@ LLVM_LIBC_FUNCTION(int, printf, (const char *__restrict format, ...)) {
return -1;
}
- if (retval.value >= cpp::numeric_limits<int>::max()) {
+ if (retval.value > cpp::numeric_limits<int>::max()) {
libc_errno = EOVERFLOW;
return -1;
}
diff --git a/libc/src/stdio/baremetal/vprintf.cpp b/libc/src/stdio/baremetal/vprintf.cpp
index 7dcf01280685f..992618d062b0d 100644
--- a/libc/src/stdio/baremetal/vprintf.cpp
+++ b/libc/src/stdio/baremetal/vprintf.cpp
@@ -22,7 +22,7 @@ namespace LIBC_NAMESPACE_DECL {
namespace {
LIBC_INLINE int stdout_write_hook(cpp::string_view new_str, void *) {
- write_to_stdout(new_str);
+ write_to_stdout(new_str);
return printf_core::WRITE_OK;
}
@@ -53,7 +53,7 @@ LLVM_LIBC_FUNCTION(int, vprintf,
}
- if (retval.value >= cpp::numeric_limits<int>::max()) {
+ if (retval.value > cpp::numeric_limits<int>::max()) {
libc_errno = EOVERFLOW;
return -1;
}
diff --git a/libc/src/stdio/printf_core/core_structs.h b/libc/src/stdio/printf_core/core_structs.h
index ab6c9228fd76f..3cb76ed32776f 100644
--- a/libc/src/stdio/printf_core/core_structs.h
+++ b/libc/src/stdio/printf_core/core_structs.h
@@ -31,7 +31,7 @@ struct PrintfResult {
constexpr bool has_error() { return error != 0; }
- // constexpr operator size_t() { return value; }
+ constexpr operator size_t() { return value; }
};
// These length modifiers match the length modifiers in the format string, which
diff --git a/libc/src/stdio/printf_core/printf_main.h b/libc/src/stdio/printf_core/printf_main.h
index 7bb5b3f3d1cf5..f187b43a9cd8f 100644
--- a/libc/src/stdio/printf_core/printf_main.h
+++ b/libc/src/stdio/printf_core/printf_main.h
@@ -30,10 +30,9 @@ PrintfResult printf_main(Writer<write_mode> *writer, const char *__restrict str,
!cur_section.raw_string.empty();
cur_section = parser.get_next_section()) {
if (cur_section.has_conv)
- result = convert(writer, cur_section); // look at usages
+ result = convert(writer, cur_section);
else
- result = writer->write(cur_section.raw_string); // look at usages
-
+ result = writer->write(cur_section.raw_string);
if (result < 0)
return {0, -result};
}
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