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Re: [PATCH 03/14] Define SNPRINTF_SIZE_CORR=1 for Microsoft Visual C++

From
Johannes Sixt <j6t@kdbg.org>
Date
Aug 21, 2009, 21:41 UTC
Message-ID
<200908212341.37531.j6t@kdbg.org>
In-Reply-To
<7vr5v4dgz0.fsf@alter.siamese.dyndns.org>
On Freitag, 21. August 2009, Junio C Hamano wrote:
Show 14 quoted lines
> Marius Storm-Olsen <mstormo@gmail.com> writes:
> > From: Frank Li <lznuaa@gmail.com>
> >
> > The Microsoft C runtime's vsnprintf function does not add NUL at
> > the end of the buffer.
>
> This contradicts the way I read the comment in compat/snprintf.c from
> f4626df (Add target architecture MinGW., 2007-12-01).
>
> As far as I can see, the correction is about the meaning of the size
> parameter to the function, namely, that a broken implementation may
> mistakenly think that it was told the maximum length of the meat of the
> string to write, and it is allowed to append a NUL beyond the limit, when
> the caller actually is telling it the size of the buffer.

Not quite. The parameter *is* the size of the buffer and vsnprintf does not write beyond the buffer. However, it has the awkward behavior that if the buffer is too short by exactly one byte, i.e. there is room for the complete string, but not for the terminating NUL, then vsnprintf does not report an error!

Therefore, we tell vsnprintf that the buffer is shorter by one byte and always write NUL in the last position so that we get a correctly terminated string even in this case.

-- Hannes
Previous: Johan 't HartNext: Junio C Hamano
Message 38 of 49 in “Build git with MSVC”
  1. 00/14 Build git with MSVCMarius Storm-Olsen, Aug 21, 2009
  2. 01/14 Fix non-constant array creationMarius Storm-Olsen, Aug 21, 2009
  3. 02/14 Avoid declaration after statementMarius Storm-Olsen, Aug 21, 2009
  4. 03/14 Define SNPRINTF_SIZE_CORR=1 for Microsoft Visual C++Marius Storm-Olsen, Aug 21, 2009
  5. 04/14 Add define guards to compat/win32.hMarius Storm-Olsen, Aug 21, 2009
  6. 05/14 Change regerror() declaration from K&R style to ANSI C (C89)Marius Storm-Olsen, Aug 21, 2009
  7. 06/14 mingw.c: Use the O_BINARY flag to open filesMarius Storm-Olsen, Aug 21, 2009
  8. 07/14 Fix __stdcall/WINAPI placement and function prototypeMarius Storm-Olsen, Aug 21, 2009
  9. 08/14 Test for WIN32 instead of __MINGW32_Marius Storm-Olsen, Aug 21, 2009
  10. 09/14 Avoid including windows.h in winansi.c for MSVC buildMarius Storm-Olsen, Aug 21, 2009
  11. 10/14 Add empty header files for MSVC portMarius Storm-Olsen, Aug 21, 2009
  12. 11/14 Add MinGW header files to build git with MSVCMarius Storm-Olsen, Aug 21, 2009
  13. 12/14 Add platform files for MSVC portingMarius Storm-Olsen, Aug 21, 2009
  14. 13/14 Add MSVC project filesMarius Storm-Olsen, Aug 21, 2009
  15. 14/14 Add README and gitignore file for MSVC buildMarius Storm-Olsen, Aug 21, 2009
  16. Thiago FarinaAug 23, 2009
  17. Reece DunnAug 23, 2009
  18. Marius Storm-OlsenAug 23, 2009
  19. Thiago FarinaAug 23, 2009
  20. Marius Storm-OlsenAug 24, 2009
  21. Frank LiAug 25, 2009
  22. Thiago FarinaAug 25, 2009
  23. Frank LiAug 27, 2009
  24. Thiago FarinaAug 27, 2009
  25. Erik Faye-LundSep 7, 2009
  26. Junio C HamanoAug 21, 2009
  27. Reece DunnAug 21, 2009
  28. Marius Storm-OlsenAug 22, 2009
  29. Paolo BonziniAug 28, 2009
  30. Johannes SixtAug 21, 2009
  31. Marius Storm-OlsenAug 21, 2009
  32. Frank LiAug 21, 2009
  33. 05/14 Change regerror() definition from K&R style to ANSI C (C89)Marius Storm-Olsen, Aug 21, 2009
  34. Frank LiAug 22, 2009
  35. Erik Faye-LundAug 24, 2009
  36. Junio C HamanoAug 21, 2009
  37. Johan 't HartAug 21, 2009
  38. Johannes SixtAug 21, 2009
  39. Junio C HamanoAug 21, 2009
  40. Marius Storm-OlsenAug 22, 2009
  41. Marius Storm-OlsenAug 22, 2009
  42. Erik Faye-LundAug 21, 2009
  43. Marius Storm-OlsenAug 21, 2009
  44. Janos LaubeAug 21, 2009
  45. Marius Storm-OlsenAug 21, 2009
  46. Johan 't HartAug 21, 2009
  47. Erik Faye-LundAug 22, 2009
  48. Junio C HamanoAug 21, 2009
  49. Junio C HamanoAug 21, 2009

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