[libc-commits] [libc] [libc] Implement perror (PR #143624)

[Michael Jones via libc-commits]

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@@ -0,0 +1,87 @@
+//===-- Implementation of perror ------------------------------------------===//
+//
+// 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 "src/stdio/perror.h"
+#include "src/__support/CPP/string_view.h"
+#include "src/__support/File/file.h"
+#include "src/__support/StringUtil/error_to_string.h"
+#include "src/__support/macros/config.h"
+#include "src/errno/libc_errno.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+namespace {
+
+// TODO: this is copied from `puts`, it should be moved to a shared utility.
+//  Simple helper to unlock the file once destroyed.
+struct ScopedLock {
+  ScopedLock(LIBC_NAMESPACE::File *stream) : stream(stream) { stream->lock(); }
+  ~ScopedLock() { stream->unlock(); }
+
+private:
+  LIBC_NAMESPACE::File *stream;
+};
+
+int write_out(cpp::string_view str_view, File *f) {
+  if (str_view.size() > 0) {
+    auto result = f->write_unlocked(str_view.data(), str_view.size());
+    if (result.has_error())
+      return result.error;
+  }
+  return 0;
+}
+
+} // namespace
+
+// TODO: this seems like there should be some sort of queue system to
+// deduplicate this code.
+LLVM_LIBC_FUNCTION(void, perror, (const char *str)) {
+  const char empty_str[1] = {'\0'};
+  if (str == nullptr)
+    str = empty_str;
+  cpp::string_view str_view(str);
+
+  auto err_str = get_error_string(libc_errno);
+
+  // We need to lock the stream to ensure the newline is always appended.
+  ScopedLock lock(LIBC_NAMESPACE::stderr);
----------------
michaelrj-google wrote:

Is this better?

https://github.com/llvm/llvm-project/pull/143624