Le 5 nov. 2012 à 09:08, Eli Friedman <[email protected]> a écrit :
> On Sun, Nov 4, 2012 at 3:10 PM, Andy Gibbs <[email protected]> wrote: >> Hi, >> >> Please could someone review the attached patch for me before I commit it. >> >> This patch fixes the rules surrounding the removal of a leading comma where >> a __VA_ARGS__ expansion is empty. >> >> GCC has the extension, implemented already in clang for... >> >> #define M(...) call(a, ## __VA_ARGS__) >> >> This will expand to "call(a)" for "M()", removing the comma. However, under >> -std=c99, this behaviour changes so that the comma is not removed. The >> attached patch follows this behaviour when in c99 mode in clang. In gnu99 >> mode, it behaves as before, and similarly for pre-c99 dialects and for c++ >> (all checked against gcc's behaviour). > > Why do we need to change the behavior in C99 mode? As far as I can > tell, it's impossible to construct a strictly conforming program for > which the C99 standard specifies behavior different from the gcc > extension. It's going to break a lot of code. clang defaults to C99 (as does Xcode projects) and a lot of code rely on this behavior. -- Jean-Daniel _______________________________________________ cfe-commits mailing list [email protected] http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
