Re: Question for ISO C standards gurus

[law at redhat dot com]

In message <1080348071.4600.244.camel@localhost.localdomain>, Diego Novillo wri
tes:
 >On Thu, 2004-03-25 at 13:08, Dave Korn wrote:
 >
 >> "Here is the complete list of all sequence points in C++: 
 >> 
 >> at the end of a full expression 
 >> 
 >> after the evaluation of all function arguments in a function call and befor
 >e
 >> execution of any expressions in the function body 
 >> 
 >> after copying of a returned value and before execution of any expressions
 >> outside the function 
 >> 
 >> after evaluation of the first expression in a&&b,  a||b,  a?b:c,  or  a,b 
 >> 
 >> after the initialization of each base and member in the constructor
 >> initialization list "
 >> 
 >So, the program below should print 5?  It certainly doesn't with gcc 3.2
 >nor mainline:
No, it should print 4.

First you evaluate the argument to produce the passed-in value, note this
will not reflect any post side effects.  Then you emit the post side effects.

This effectively means that when you have post side effects that you have
to compute the value for the argument into a temporary and use the temporary
in the function call.

The ordering of stuff for a call effectively looks like

prequeue fncall
prequeue arg0
prequeue arg1
prequeue arg2
...
prequeue argn

temp0 = arg0
temp1 = arg1
temp2 = arg2
...
tempn = argn

postqueue arg0
postqueue arg1
postqueue arg2
...
postqueue argn

fncall (temp0, temp1, temp2, ... tempn)

poster fncall

Clearly for cases where there are no postqueues for a particular argument
you need not create a temporary and instead can use the evaluated argument
directly in the call.

Jeff