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Bug#372913: marked as done (gcc-4.1: datatype limits / signedness differs with optimization levels)

Your message dated Mon, 12 Jun 2006 23:31:45 +0200
with message-id <200606122331.48290.erik.meusel@web.de>
and subject line closing it
has caused the attached Bug report to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.

(NB: If you are a system administrator and have no idea what I am
talking about this indicates a serious mail system misconfiguration
somewhere.  Please contact me immediately.)

Debian bug tracking system administrator
(administrator, Debian Bugs database)
--- Begin Message --- 
Package: gcc-4.1
Version: 4.1.1-2
Severity: critical
Justification: breaks unrelated software

Use this little example to see what's happening:

#include <stdio.h>

int main(void) {
        char c = '\0';

        do {
                printf("%d\n", c);

                c++;
        } while (c != '\0');

        return 0;
}

- using -O0 as optimization level with gcc-4.1 works as expected: the values change from 0 over 127, -128 (because of the signedness) back to 0
- using -O1 with gcc-4.1 makes the values go from 0 to 255
- using -O2 (or higher) results in an infinite loop

This also occurs in gcc-snapshot and does not in gcc < 4.1.

Regards,
Erik

-- System Information:
Debian Release: testing/unstable
  APT prefers unstable
  APT policy: (500, 'unstable'), (500, 'testing'), (500, 'stable')
Architecture: i386 (i686)
Shell:  /bin/sh linked to /bin/bash
Kernel: Linux 2.6.16-2-k7
Locale: LANG=de_DE@euro, LC_CTYPE=de_DE@euro (charmap=ISO-8859-15) (ignored: LC_ALL set to de_DE@euro)

Versions of packages gcc-4.1 depends on:
ii  binutils             2.16.1cvs20060413-1 The GNU assembler, linker and bina
ii  cpp-4.1              4.1.1-2             The GNU C preprocessor
ii  gcc-4.1-base         4.1.1-2             The GNU Compiler Collection (base 
ii  libc6                2.3.6-15            GNU C Library: Shared libraries
ii  libgcc1              1:4.1.1-2           GCC support library

Versions of packages gcc-4.1 recommends:
ii  libc6-dev                     2.3.6-15   GNU C Library: Development Librari
ii  libmudflap0-dev               4.1.1-2    GCC mudflap support libraries (dev
ii  libssp0-dev                   4.1.1-2    GCC stack smashing protection libr

-- no debconf information

--- End Message ---
--- Begin Message --- 
Well, since the reported behavior seems to be a correct standard 
interpretation, I'll close the bug report now.

For anyone triggering the same problem, using -fno-tree-vrp seems to be a 
valid solution, too. It might have been a good idea to document this change 
before applying it silently, because it will break packages in testing when 
gcc 4.1 arrives and it doesn't issue any compile time error or warning.


Regards,
Erik

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