There are some known problems when using gdb on code
compiled by g77.
Inadequate investigation as of the release of 0.5.16 results in not
knowing which products are the culprit, but gdb-4.14 definitely
crashes when, for example, an attempt is made to print the contents
of a COMPLEX(KIND=2) dummy array, on at least some GNU/Linux
machines, plus some others.
Attempts to access assumed-size arrays are
also known to crash recent versions of gdb.
(gdb's Fortran support was done for a different compiler
and isn't properly compatible with g77.)