Re: use of %n in genmodes.c causes trouble on Vista

[Olivier Hainque <hainque at adacore dot com>]

Ian Lance Taylor wrote:
> What is the security issue here?  I'm not seeing it.  Are they
> concerned that attackers will modify the print control string somehow?

 I don't know. We simply have observed bootstrap problems during
 preliminary experiments on Vista, found them to be caused by
 uninitialized values of "count_" in genmodes and traced this to
 the %n issue.

 We have been using a patch almost identical to what Paolo posted, and
 and I raised the question on gcc@ to see whether this approach was
 considered correct before performing a formal test-cycle and submission
 to gcc-patches.

[...]

> This deficiency is presumably only going to arise for a mingw hosted
> gcc.  Would it be possible for the mingw startup file to call
> _set_printf_count_output?  Perhaps under the control of a command line
> option at link time?

 Maybe, I don't know either. The printf-return-value solution just looked
 straightforward, so that's the first option which came to mind, moderated
 by the potential portability question.
 
> The return value of printf is portable (unlike the return value of
> sprintf).
 
 OK, I see Paolo has committed a change along those lines already.

 Thanks much for your feedback,

 Olivier