Re: 64bit: Possible optimizer bug in g++ 4.8.0 20130319

[Corinna Vinschen <corinna-cygwin at cygwin dot com>]

On Mar 22 23:08, Christian Franke wrote:
> Thanks for providing 64-bit Cygwin.
> 
> A 64bit test build of smartmontools 6.1 segfaults after throw (It
> uses throw frequently because I replaced 'exit(status)' with 'throw
> (int)(status)' during C -> C++ migration). Changing the optimization
> level from -O2 to -O1 or -Os fixes the segfault.
> 
> I tracked this down to the attached easy testcase:

Thanks for the testcase.  I'm not a gcc expert, so I defer to Kai.
Kai, can you have a look what happens here?


Thanks,
Corinna

> $ uname -srvmo
> CYGWIN_NT-6.1 1.7.18(0.263/5/3) 2013-03-22 15:00 x86_64 Cygwin
> 
> $ g++ --version
> g++ (GCC) 4.8.0 20130319 (prerelease)
> 
> $ g++ -o throw -O1 throw.cc
> 
> $ ./throw
> 
> $ echo $?
> 42
> 
> $ g++ -o throw -O2 throw.cc
> 
> $ ./throw
> Segmentation fault
> 
> $ echo $?
> 139
> 
> Changing the size of the std::string array to <= 31 also fixes the segfault.
> 
> Hope this helps.
> 
> Christian
> 

> #include <string>
> 
> static int main_worker(int argc)
> {
>   std::string s[32]; // [31] => no segfault
>   if (argc < 2)
>     throw 42;
>   return argc;
> }
> 
> int main(int argc, char **argv)
> {
>   try {
>     return main_worker(argc);
>   }
>   catch (int i) {
>     return i;
>   }
> }


-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
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