[libc-commits] [libc] 402c376 - [libc] Change default behaviour of baremetal/printf to use stdout (#143703)

[via libc-commits]

Author: William Huynh
Date: 2025-06-16T12:22:58-07:00
New Revision: 402c376daa659c0c3a477ad038a415079ffa0a48

URL: https://github.com/llvm/llvm-project/commit/402c376daa659c0c3a477ad038a415079ffa0a48
DIFF: https://github.com/llvm/llvm-project/commit/402c376daa659c0c3a477ad038a415079ffa0a48.diff

LOG: [libc] Change default behaviour of baremetal/printf to use stdout (#143703)

In #94078, `write_to_stdout` had not been fully implemented. However,
now that it has been implemented, to conform with the C standard
(7.23.6.3. The printf function, specifically point 2), we use `stdout`.
This issue is tracked in #94685.

- Also prefer `static constexpr`
- Made it explicit that we are writing to `stdout`

Added: 
    

Modified: 
    libc/src/stdio/baremetal/printf.cpp
    libc/src/stdio/baremetal/putchar.cpp
    libc/src/stdio/baremetal/puts.cpp
    libc/src/stdio/baremetal/vprintf.cpp

Removed: 
    


################################################################################
diff  --git a/libc/src/stdio/baremetal/printf.cpp b/libc/src/stdio/baremetal/printf.cpp
index c94698ec02953..7253c6549a4e4 100644
--- a/libc/src/stdio/baremetal/printf.cpp
+++ b/libc/src/stdio/baremetal/printf.cpp
@@ -21,8 +21,8 @@ namespace LIBC_NAMESPACE_DECL {
 
 namespace {
 
-LIBC_INLINE int raw_write_hook(cpp::string_view new_str, void *) {
-  write_to_stderr(new_str);
+LIBC_INLINE int stdout_write_hook(cpp::string_view new_str, void *) {
+  write_to_stdout(new_str);
   return printf_core::WRITE_OK;
 }
 
@@ -35,11 +35,11 @@ LLVM_LIBC_FUNCTION(int, printf, (const char *__restrict format, ...)) {
                                  // and pointer semantics, as well as handling
                                  // destruction automatically.
   va_end(vlist);
-  constexpr size_t BUFF_SIZE = 1024;
+  static constexpr size_t BUFF_SIZE = 1024;
   char buffer[BUFF_SIZE];
 
   printf_core::WriteBuffer<printf_core::WriteMode::FLUSH_TO_STREAM> wb(
-      buffer, BUFF_SIZE, &raw_write_hook, nullptr);
+      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);

diff  --git a/libc/src/stdio/baremetal/putchar.cpp b/libc/src/stdio/baremetal/putchar.cpp
index 0ba46a5ade6c9..ac21e6e783b01 100644
--- a/libc/src/stdio/baremetal/putchar.cpp
+++ b/libc/src/stdio/baremetal/putchar.cpp
@@ -16,7 +16,7 @@ namespace LIBC_NAMESPACE_DECL {
 LLVM_LIBC_FUNCTION(int, putchar, (int c)) {
   char uc = static_cast<char>(c);
 
-  write_to_stderr(cpp::string_view(&uc, 1));
+  write_to_stdout(cpp::string_view(&uc, 1));
 
   return 0;
 }

diff  --git a/libc/src/stdio/baremetal/puts.cpp b/libc/src/stdio/baremetal/puts.cpp
index 5062efda1c0dc..fcd3aa086b2bf 100644
--- a/libc/src/stdio/baremetal/puts.cpp
+++ b/libc/src/stdio/baremetal/puts.cpp
@@ -17,8 +17,8 @@ LLVM_LIBC_FUNCTION(int, puts, (const char *__restrict str)) {
   cpp::string_view str_view(str);
 
   // TODO: Can we combine these to avoid needing two writes?
-  write_to_stderr(str_view);
-  write_to_stderr("\n");
+  write_to_stdout(str_view);
+  write_to_stdout("\n");
 
   return 0;
 }

diff  --git a/libc/src/stdio/baremetal/vprintf.cpp b/libc/src/stdio/baremetal/vprintf.cpp
index 3e8631abd90d9..ab02533f14911 100644
--- a/libc/src/stdio/baremetal/vprintf.cpp
+++ b/libc/src/stdio/baremetal/vprintf.cpp
@@ -21,8 +21,8 @@ namespace LIBC_NAMESPACE_DECL {
 
 namespace {
 
-LIBC_INLINE int raw_write_hook(cpp::string_view new_str, void *) {
-  write_to_stderr(new_str);
+LIBC_INLINE int stdout_write_hook(cpp::string_view new_str, void *) {
+  write_to_stdout(new_str);
   return printf_core::WRITE_OK;
 }
 
@@ -33,11 +33,11 @@ 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.
-  constexpr size_t BUFF_SIZE = 1024;
+  static constexpr size_t BUFF_SIZE = 1024;
   char buffer[BUFF_SIZE];
 
   printf_core::WriteBuffer<printf_core::WriteMode::FLUSH_TO_STREAM> wb(
-      buffer, BUFF_SIZE, &raw_write_hook, nullptr);
+      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);