GDB fails to open file when debugging f77 program

Question

So I'm not a big CS guy, so bear with me as I try to explain this adequately enough.

At work, I use a program written in Fortran 77 to do some modeling. Our debugging has been an issue, due to some IT constraints that are outside my control. When we attempt to use GDB, the compiler loads. When you run the program, it fails through internal logic checks. The program's looking for an input file, but it can't find it because GDB does not load another file that has a list of all the directories the input file, and other relevant files, could possibly be in.

The relevant code:

...
logical exst
...
INQUIRE(FILE='KEYWORDS',EXTST=exst)
if(exst)then
...
endif

End code

This DOES work when I run the program. The KEYWORDS file is found, read in through a call within the if statement branch, which allows the program to find the input file. When debugging, however, exst is always false, preventing proper read in, and failing later through logic checks.

Does GDB require certain permissions? The only thing I could find in my own search was a possible issue on signed/unsigned reported file size incompatibility, but outside of understanding what signed and unsigned values are, the explanation was a bit over my head.

Any help is appreciated. Will try to provide more information where requested.

Tom Tromey · Accepted Answer · 2015-02-18 19:02:22Z

1

gdb doesn't change the permissions of the program it runs. It runs under the same user id, as usual.

Normally when this sort of problem arises, it comes from an environmental difference. Typical sources are the current working directory, the command-line arguments, or environment variables. It's also reasonably common to have a wrapper script that invokes a program properly, but then when running in gdb, one does not use the wrapper and then improperly duplicates the setup that it provides. Less common but also still possible is code in .gdbinit messing with the environment inside gdb. So be sure to double-check things with pwd inside gdb, etc.

answered Feb 18, 2015 at 19:02

Tom Tromey

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Jeff Layton Over a year ago

I've ensured I'm within the right directory during a debugging session. Will check the .gdbinit suggestion

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