Re: target/3850: gcc 2.73-3.0 code generation on HP and SUN WRONG

Re: target/3850: gcc 2.73-3.0 code generation on HP and SUN WRONG

[aoliva]

Synopsis: gcc 2.73-3.0  code generation on HP and SUN WRONG

State-Changed-From-To: open->closed
State-Changed-By: aoliva
State-Changed-When: Sat Jul 28 19:54:45 2001
State-Changed-Why:
    It is the expectation that is wrong.  There's no sequence point between arguments to a function call.  Not only can they be executed in any order, but also, their evaluations can be interleaved.  The C Standard says that this code invokes undefined behavior, so as to place no limits on the amount of optimization a compiler can do on this kind of code.  If your code depends on any particular order of execution, the code is in error, and should be fixed by inserting sequence points between expressions that modify the same variable.  There's a sequence point between consecutive commands (semicolon) and between expressions separated by the comma operator (comma), but not when the comma is only used to separate arguments.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view&pr=3850&database=gcc

target/3850: gcc 2.73-3.0 code generation on HP and SUN WRONG

[daniel]

>Number:         3850
>Category:       target
>Synopsis:       gcc 2.73-3.0  code generation on HP and SUN WRONG
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Fri Jul 27 14:36:01 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator:     Daniel Sittig
>Release:        unknown-1.0
>Organization:
>Environment:
On HP: HPUX 10.20, PA85000	
ON SUN: Solaris 2.6, UII 
>Description:
The code generation for example printf function call
is wrong: ( it is not printf specific ! )

int a;
printf("a=%d a=%d", (a=1,a), (a=2,a));

The expected output shall be : a=1 a=2

But this works only on a x86 , both UII and HP PA fails.
I was dissassembling it and found that ALL Gcc we have 
create ONE memory reference for variable 'a'. 
I was doublechecking with HP 'cc' and it created correctly
2 memory references thus displaying the expected result.
Linux is applying a 'pushd' before loading '2' to %eax.
This also works and the example above works correctly.

>How-To-Repeat:
gcc mini.c -g
gdb a.out
disassemble
>Fix:
No fix known. 
>Release-Note:
>Audit-Trail:
>Unformatted:
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