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

[via libc-commits]

https://github.com/saturn691 updated https://github.com/llvm/llvm-project/pull/143703

>From 5616dad33b76a7eb0ca5dcaa9d1eca5e14a2f6b2 Mon Sep 17 00:00:00 2001
From: William Huynh <William.Huynh at arm.com>
Date: Wed, 11 Jun 2025 14:35:11 +0100
Subject: [PATCH 1/2] Change default behaviour of baremetal/printf to use
 stdout

---
 libc/src/stdio/baremetal/printf.cpp  | 8 ++++----
 libc/src/stdio/baremetal/putchar.cpp | 2 +-
 libc/src/stdio/baremetal/puts.cpp    | 4 ++--
 libc/src/stdio/baremetal/vprintf.cpp | 8 ++++----
 4 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/libc/src/stdio/baremetal/printf.cpp b/libc/src/stdio/baremetal/printf.cpp
index c94698ec02953..9814edb556faf 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 raw_write_stdout_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, &raw_write_stdout_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..4fa1ae00dd61c 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 raw_write_stdout_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, &raw_write_stdout_hook, nullptr);
   printf_core::Writer<printf_core::WriteMode::FLUSH_TO_STREAM> writer(wb);
 
   int retval = printf_core::printf_main(&writer, format, args);

>From cde8ed1e0ae27ef55d1752acaeef6beab4847432 Mon Sep 17 00:00:00 2001
From: William Huynh <William.Huynh at arm.com>
Date: Wed, 11 Jun 2025 20:22:27 +0100
Subject: [PATCH 2/2] fixup! Change default behaviour of baremetal/printf to
 use stdout

---
 libc/src/stdio/baremetal/printf.cpp  | 4 ++--
 libc/src/stdio/baremetal/vprintf.cpp | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/libc/src/stdio/baremetal/printf.cpp b/libc/src/stdio/baremetal/printf.cpp
index 9814edb556faf..7253c6549a4e4 100644
--- a/libc/src/stdio/baremetal/printf.cpp
+++ b/libc/src/stdio/baremetal/printf.cpp
@@ -21,7 +21,7 @@ namespace LIBC_NAMESPACE_DECL {
 
 namespace {
 
-LIBC_INLINE int raw_write_stdout_hook(cpp::string_view new_str, void *) {
+LIBC_INLINE int stdout_write_hook(cpp::string_view new_str, void *) {
   write_to_stdout(new_str);
   return printf_core::WRITE_OK;
 }
@@ -39,7 +39,7 @@ LLVM_LIBC_FUNCTION(int, printf, (const char *__restrict format, ...)) {
   char buffer[BUFF_SIZE];
 
   printf_core::WriteBuffer<printf_core::WriteMode::FLUSH_TO_STREAM> wb(
-      buffer, BUFF_SIZE, &raw_write_stdout_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/vprintf.cpp b/libc/src/stdio/baremetal/vprintf.cpp
index 4fa1ae00dd61c..ab02533f14911 100644
--- a/libc/src/stdio/baremetal/vprintf.cpp
+++ b/libc/src/stdio/baremetal/vprintf.cpp
@@ -21,7 +21,7 @@ namespace LIBC_NAMESPACE_DECL {
 
 namespace {
 
-LIBC_INLINE int raw_write_stdout_hook(cpp::string_view new_str, void *) {
+LIBC_INLINE int stdout_write_hook(cpp::string_view new_str, void *) {
   write_to_stdout(new_str);
   return printf_core::WRITE_OK;
 }
@@ -37,7 +37,7 @@ LLVM_LIBC_FUNCTION(int, vprintf,
   char buffer[BUFF_SIZE];
 
   printf_core::WriteBuffer<printf_core::WriteMode::FLUSH_TO_STREAM> wb(
-      buffer, BUFF_SIZE, &raw_write_stdout_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);