On Sun, Jul 10, 2011 at 5:47 AM, Paul Eggert <egg...@cs.ucla.edu> wrote: > On 07/09/11 15:32, James Youngman wrote: >> Is there a way of eliminating this false positive which doesn't force >> me to give up -Wvla? > > You can use a pragma in the module that you've audited. > The pragma would tell GCC, "don't waste my time warning > about VLAs in this module".
I can't see a way of making this strategy conveniently work, since there the VLA is in gettext.h, which will be included by a number of source files. Adding #pragma GCC ignored -Wvla to gettexzt.h would result in VLA warnings being suppressed for any module which uses gettext.h, which is one of the things I was trying to avoid. While I could balance this by remembering to put #pragma GCC warning -Wvla in my source files after all the includes, it seems to me I'm no more likely to remember to do that than to avoid using VLAs in the first place. This would also take away from the user the configure-time control they currently have over what warning flags are turned on or off. Something I haven't tried yet it a configure.ac change; if we discover in configure that -Wvla is in CFLAGS and the compiler is GCC, we could add this: #pragma GCC diagnostic error "-Wvla" ... presumably if done correctly this would cause configure to set _LIBGETTEXT_HAVE_VARIABLE_SIZE_ARRAYS to 0. This method seems suboptimal to me though, since as I mentioned earlier in the thread, the ideal thing would be to allow VLAs in parts of the code which are protected by something like _LIBGETTEXT_HAVE_VARIABLE_SIZE_ARRAYS. A function-level pragma would probably be ideal here, but unfortunately they can only be used to tweak optimisation and function attributes. James.
