http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49679
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution| |INVALID
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-07-08
17:57:09 UTC ---
The code has undefined behaviour because there are no sequence points between
the increments, see http://c-faq.com/expr/seqpoints.html
GCC even warns you:
seq.cc: In function 'int main(int, char**)':
seq.cc:19:15: warning: operation on 'a' may be undefined [-Wsequence-point]
seq.cc:19:15: warning: operation on 'a' may be undefined [-Wsequence-point]
seq.cc:20:15: warning: operation on 'b' may be undefined [-Wsequence-point]
seq.cc:20:15: warning: operation on 'b' may be undefined [-Wsequence-point]
You should use -Wall if the compiler seems to be doing something you don't
understand, it might explain why.
