Re: Enforcing order of execution for function arguments

[Andrew Haley <aph at redhat dot com>]

Chris Jefferson writes:

 > One thing which comes up regularly in various C and C++
 > messageboards is that statements like "f() + g()" and "a(f(), g())"
 > do not declare which order f() and g() will be executed in.
 > 
 > How hard would it be to fix the order of execution in gcc/g++?
 > Could someone point me to the piece of code which must change, or
 > if it is only a very small change, the actual change required? I
 > would very much like to be able to benchmark this, as I can find no
 > previous case where someone has tried fixing the order of execution
 > to see if it actually makes any measureable difference.

The easiest way is during gimplification: you'd walk over the arglist
from left to right, calling

        gimplify_expr (&arg, pre_p, post_p,
		       is_gimple_formal_tmp_var, fb_rvalue);

on each arg.

 > Would anyone be interested in this being added as a command line argument?

That would be a Bad Thing.

Andrew.