[libc-commits] [libc] [libc] Refactor strftime internals to handle size_t return values (PR #166901)

[Marcell Leleszi via libc-commits]

https://github.com/mleleszi updated https://github.com/llvm/llvm-project/pull/166901

>From 9c4f8fd5db7a752abcf446a3242910aa669b012c Mon Sep 17 00:00:00 2001
From: Marcell Leleszi <mleleszi at google.com>
Date: Fri, 7 Nov 2025 06:37:42 +0000
Subject: [PATCH 1/2] Refactor strftime_main to return ErrorOr<size_t>

---
 libc/src/time/strftime.cpp                  |  5 +++--
 libc/src/time/strftime_core/strftime_main.h | 10 +++++-----
 libc/src/time/strftime_l.cpp                |  4 ++--
 3 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/libc/src/time/strftime.cpp b/libc/src/time/strftime.cpp
index 89b7d9bb7c1b9..1f7f55a40249e 100644
--- a/libc/src/time/strftime.cpp
+++ b/libc/src/time/strftime.cpp
@@ -23,10 +23,11 @@ LLVM_LIBC_FUNCTION(size_t, strftime,
       printf_core::WriteMode::FILL_BUFF_AND_DROP_OVERFLOW>::value>
       wb(buffer, (buffsz > 0 ? buffsz - 1 : 0));
   printf_core::Writer writer(wb);
-  int ret = strftime_core::strftime_main(&writer, format, timeptr);
+  auto ret = strftime_core::strftime_main(&writer, format, timeptr);
   if (buffsz > 0) // if the buffsz is 0 the buffer may be a null pointer.
     wb.buff[wb.buff_cur] = '\0';
-  return (ret < 0 || static_cast<size_t>(ret) >= buffsz) ? 0 : ret;
+  return (!ret.has_value() || ret.value() >= buffsz) ? 0 : ret.value();
+  ;
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/time/strftime_core/strftime_main.h b/libc/src/time/strftime_core/strftime_main.h
index 2b136d83234cd..855a44107914c 100644
--- a/libc/src/time/strftime_core/strftime_main.h
+++ b/libc/src/time/strftime_core/strftime_main.h
@@ -10,6 +10,7 @@
 #define LLVM_LIBC_SRC_STDIO_STRFTIME_CORE_STRFTIME_MAIN_H
 
 #include "hdr/types/struct_tm.h"
+#include "src/__support/error_or.h"
 #include "src/__support/macros/config.h"
 #include "src/stdio/printf_core/writer.h"
 #include "src/time/strftime_core/converter.h"
@@ -20,8 +21,8 @@ namespace LIBC_NAMESPACE_DECL {
 namespace strftime_core {
 
 template <printf_core::WriteMode write_mode>
-int strftime_main(printf_core::Writer<write_mode> *writer,
-                  const char *__restrict str, const tm *timeptr) {
+ErrorOr<size_t> strftime_main(printf_core::Writer<write_mode> *writer,
+                              const char *__restrict str, const tm *timeptr) {
   Parser parser(str);
   int result = 0;
   for (strftime_core::FormatSection cur_section = parser.get_next_section();
@@ -33,11 +34,10 @@ int strftime_main(printf_core::Writer<write_mode> *writer,
       result = writer->write(cur_section.raw_string);
 
     if (result < 0)
-      return result;
+      return Error(-result);
   }
 
-  // TODO: Use ErrorOr<size_t>
-  return static_cast<int>(writer->get_chars_written());
+  return writer->get_chars_written();
 }
 
 } // namespace strftime_core
diff --git a/libc/src/time/strftime_l.cpp b/libc/src/time/strftime_l.cpp
index 409f8683b7289..2ec90634ea347 100644
--- a/libc/src/time/strftime_l.cpp
+++ b/libc/src/time/strftime_l.cpp
@@ -26,10 +26,10 @@ LLVM_LIBC_FUNCTION(size_t, strftime_l,
       printf_core::WriteMode::FILL_BUFF_AND_DROP_OVERFLOW>::value>
       wb(buffer, (buffsz > 0 ? buffsz - 1 : 0));
   printf_core::Writer writer(wb);
-  int ret = strftime_core::strftime_main(&writer, format, timeptr);
+  auto ret = strftime_core::strftime_main(&writer, format, timeptr);
   if (buffsz > 0) // if the buffsz is 0 the buffer may be a null pointer.
     wb.buff[wb.buff_cur] = '\0';
-  return (ret < 0 || static_cast<size_t>(ret) >= buffsz) ? 0 : ret;
+  return (!ret.has_value() || ret.value() >= buffsz) ? 0 : ret.value();
 }
 
 } // namespace LIBC_NAMESPACE_DECL

>From 60edf2fe28b603298be687ab60603776b7a60829 Mon Sep 17 00:00:00 2001
From: Marcell Leleszi <mleleszi at google.com>
Date: Fri, 7 Nov 2025 07:04:41 +0000
Subject: [PATCH 2/2] Add deps to cmake

---
 libc/src/time/strftime_core/CMakeLists.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/libc/src/time/strftime_core/CMakeLists.txt b/libc/src/time/strftime_core/CMakeLists.txt
index 3ffd283ead7fe..a9aa573cc9a63 100644
--- a/libc/src/time/strftime_core/CMakeLists.txt
+++ b/libc/src/time/strftime_core/CMakeLists.txt
@@ -43,6 +43,7 @@ add_header_library(
     .core_structs
     .parser
     .converter
+    libc.src.__support.error_or
     libc.src.stdio.printf_core.writer
     libc.hdr.types.struct_tm
 )