base/allocator/partition_allocator/src/partition_alloc/partition_alloc_base/strings/stringprintf.cc

// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "partition_alloc/partition_alloc_base/strings/stringprintf.h"

#include "partition_alloc/partition_alloc_base/compiler_specific.h"
#include "partition_alloc/partition_alloc_base/scoped_clear_last_error.h"

#include <stdarg.h>
#include <stdio.h>

namespace partition_alloc::internal::base {

std::string PA_PRINTF_FORMAT(1, 2)
    TruncatingStringPrintf(const char* format, ...) {
  base::ScopedClearLastError last_error;
  char stack_buf[kMaxLengthOfTruncatingStringPrintfResult + 1];
  va_list arguments;
  va_start(arguments, format);
#if BUILDFLAG(IS_WIN)
  int result = vsnprintf_s(stack_buf, std::size(stack_buf), _TRUNCATE, format,
                           arguments);
#else
  int result = vsnprintf(stack_buf, std::size(stack_buf), format, arguments);
#endif
  va_end(arguments);
#if BUILDFLAG(IS_WIN)
  // If an output error is encountered or data is larger than count,
  // a negative value is returned. So to see whether an output error is really
  // encountered or not, need to see errno. If errno == EINVAL or
  // errno == ERANGE, an output error is encountered. If not, an output is
  // just truncated.
  if (result < 0 && (errno == EINVAL || errno == ERANGE)) {
    return std::string();
  }
#else
  // If an output error is encountered, a negative value is returned.
  // In the case, return an empty string.
  if (result < 0) {
    return std::string();
  }
#endif
  // If result is equal or larger than std::size(stack_buf), the output was
  // truncated. ::base::StringPrintf doesn't truncate output.
  return std::string(stack_buf);
}

}  // namespace partition_alloc::internal::base