g77/gfortran

[Tobias Burnus]

Hi,

Granville Sewell wrote:
>  A program that ran when compiled with g77 produces the following result 
>  when compiled with gfortran and executed: 
>
> /root/bin/runpde2d: line 60:  4076 Segmentation fault      ./a.out
>
>  When compiled using g77 we had to set the stacksize limit
>  (limit stacksize 128000) to avoid this error, but that doesn't help
>  with gfortran.  I realize this probably isn't enough information to
>  allow a diagnosis, but thought I'd take a shot.  Any compiler options
>  you might suggest for gfortran?
>   
Well, first of all use -fbounds-check.
Secondly, compile with "-g" and run in a debugger; do a backtrace ("bt"
in gdb) when the program crashes to find out where it crashes.
Thirdly, if you have valgrind, running the binary (compiled with "-g")
through valgrind might also find problems. (This slows down the
execution a lot; if it crashes after hours of calculations, this won't
work well.)

You can tune the usage of the stack using -fmax-stack-var-size=; using
RECURSIVE procedures will increase the needed stack size, however.

Otherwise it is extremely difficult to guess the reason of a crash as
there are millions of possibilities, which cannot narrowed down without
further information.

Tobias