[flac-dev] vsnprintf_s and vsnprintf

[lvqcl]

Erik de Castro Lopo wrote:

>> Oops. It seems that vsnprintf_s isn't always available on MinGW platform:
>> MinGW declares this function only if MINGW_HAS_SECURE_API macro is defined.
>> That's because WinXP version of msvcrt.dll doesn't contain secure functions
>> like vsnprintf_s.
>>
>> Maybe it's better to revert vsnprintf_s to vsprintf or to use vnsprintf?
>
> Ok, we need to drop vsnprintf_s to support WinXP. I'd prefer vsnprintf
> over vsprintf but have no way of testing any of these options.


I wrote a small program that fills a buffer[] with "abcdefghijklmnopqrstuvwxyz\0"
pattern and then tries to write "0123456789" string into it.
It calls either
	ret = vsnprintf_s(buffer, buf_size, _TRUNCATE, fmt, va);
or
	ret = vsnprintf(buffer, buf_size, fmt, va);

  The results are:
  ---------------------------------------------------------------------------
  vsnprintf_s (MSVC, MinGW):

  buf_size = 8;        ret = -1;        buffer = "0123456"
  buf_size = 9;        ret = -1;        buffer = "01234567"
  buf_size = 10;       ret = -1;        buffer = "012345678"
  buf_size = 11;       ret = 10;        buffer = "0123456789"
  buf_size = 12;       ret = 10;        buffer = "0123456789"
  ---------------------------------------------------------------------------

  vsnprintf (MSVC, MinGW):

  buf_size = 8;        ret = -1;        buffer = "01234567ijklmnopqrstuvwxyz"
  buf_size = 9;        ret = -1;        buffer = "012345678jklmnopqrstuvwxyz"
  buf_size = 10;       ret = 10;        buffer = "0123456789klmnopqrstuvwxyz"
  buf_size = 11;       ret = 10;        buffer = "0123456789"
  buf_size = 12;       ret = 10;        buffer = "0123456789"
  ---------------------------------------------------------------------------

  vsnprintf (MinGW with "#define __USE_MINGW_ANSI_STDIO 1"):

  buf_size = 8;        ret = 10;        buffer = "0123456"
  buf_size = 9;        ret = 10;        buffer = "01234567"
  buf_size = 10;       ret = 10;        buffer = "012345678"
  buf_size = 11;       ret = 10;        buffer = "0123456789"
  buf_size = 12;       ret = 10;        buffer = "0123456789"
  ---------------------------------------------------------------------------


By the way... according to MSDN page for CreateProcess() function
<http://msdn.microsoft.com/en-us/library/windows/desktop/ms682425(v=vs.85).aspx>:
"The maximum length of [the command line] is 32,768 characters, including the Unicode terminating null character".

UTF-8 uses up to 4 bytes for a character, so the maximum length of
a temporary buffer for a call like

	flac_fprintf(stderr, "%s: ERROR: couldn't get block from chain\n", filename);

should in theory exceed 4*32768 = 131072 bytes (plus some space for
the rest of the message).

Currently *printf_utf8() functions allocate 32768 bytes buffer.