c/2600: gcc fails to increment a signed int variable by one with -O2

c/2600: gcc fails to increment a signed int variable by one with -O2

[matthieu.moy]

>Number:         2600
>Category:       c
>Synopsis:       gcc fails to increment a signed int variable by one with -O2
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Fri Apr 20 07:26:00 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator:     Matthieu Moy
>Release:        gcc version 2.95.3
>Organization:
>Environment:
AIX on bull (8 procs)
>Description:
A variable plus one operation is not done if the program 
is compiled with optimisation -O2 in a very simple c program.

example of output :
$ gcc -O1 bug-gcc.c
$ a.out
i = 1; plus_one = 2
$ gcc -O2 bug-gcc.c
$ a.out
i = 1; plus_one = 1
>How-To-Repeat:
compile with -O1 and -O2
>Fix:
I didn't make any patch
>Release-Note:
>Audit-Trail:
>Unformatted:
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