[libc-commits] [libc] [libc] Add putc, fputc, and fprintf to stdio/baremetal (PR #144567)

[Michael Jones via libc-commits]

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@@ -0,0 +1,48 @@
+//===-- Baremetal helper functions for writing to stdout/stderr -*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "hdr/stdio_macros.h" // For stdout/err
+#include "hdr/types/FILE.h"
+#include "src/__support/CPP/string_view.h"
+#include "src/__support/OSUtil/io.h"
+#include "src/__support/macros/config.h"
+#include "src/stdio/printf_core/core_structs.h" // For printf_core::WRITE_OK
+
+#include <stddef.h>
+
+namespace LIBC_NAMESPACE_DECL {
+namespace {
+
+LIBC_INLINE int stdout_write_hook(cpp::string_view new_str, void *) {
+  write_to_stdout(new_str);
+  return printf_core::WRITE_OK;
+}
+
+LIBC_INLINE int stderr_write_hook(cpp::string_view new_str, void *) {
+  write_to_stderr(new_str);
+  return printf_core::WRITE_OK;
+}
+
+LIBC_INLINE void write(::FILE *f, cpp::string_view new_str) {
+  if (f == stdout) {
+    write_to_stdout(new_str);
+  } else {
+    write_to_stderr(new_str);
+  }
+}
+
+LIBC_INLINE decltype(&stdout_write_hook) get_write_hook(::FILE *f) {
----------------
michaelrj-google wrote:

instead of having a decltype here, use something like
```
  using StreamWriter = int (*)(cpp::string_view, void *);
```

https://github.com/llvm/llvm-project/pull/144567