A simple question on expression

[dewar@gnat.com]

<<why
a = 0?0:a++;
not be expanded to
>>

It could be, but there is no requirement for it to be so expanded. You 
are writing code whose meaning is defined neither by K&R nor by the
ANSI standard, so asking questions about how it is compiled is a waste
of time. This is a C issue, not a GCC issue, so you should take it to
an appropriate newsgroup at this stage if you are still confused on the
C rules.