[Bug fortran/51522] ICE in gfortran 4.6.2, x86_64

["jb at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51522

--- Comment #9 from Janne Blomqvist <jb at gcc dot gnu.org> 2012-02-05 21:04:18 UTC ---
So the complete valgrind error message I get (with the comment #4 testcase
fixed per Tobias instructions in comment #6) is:

==14281== Invalid read of size 4
==14281==    at 0x528B66: resolve_symbol (resolve.c:10559)
==14281==    by 0x545EF0: do_traverse_symtree (symbol.c:3386)
==14281==    by 0x532503: resolve_types (resolve.c:13859)
==14281==    by 0x527473: gfc_resolve (resolve.c:13959)
==14281==    by 0x528C18: resolve_symbol (resolve.c:12715)
==14281==    by 0x545EF0: do_traverse_symtree (symbol.c:3386)
==14281==    by 0x532503: resolve_types (resolve.c:13859)
==14281==    by 0x527473: gfc_resolve (resolve.c:13959)
==14281==    by 0x51ABBC: gfc_parse_file (parse.c:4594)
==14281==    by 0x557315: gfc_be_parse_file (f95-lang.c:250)
==14281==    by 0x909CDC: do_compile (toplev.c:557)
==14281==    by 0x90A853: toplev_main (toplev.c:2014)
==14281==  Address 0x5ca8700 is 32 bytes inside a block of size 304 free'd
==14281==    at 0x4C270BD: free (vg_replace_malloc.c:366)
==14281==    by 0x546E91: gfc_undo_symbols (symbol.c:2898)
==14281==    by 0x514F5A: reject_statement (parse.c:1743)
==14281==    by 0x515A54: decode_statement (parse.c:316)
==14281==    by 0x516D8C: next_statement (parse.c:778)
==14281==    by 0x51801D: parse_spec (parse.c:2379)
==14281==    by 0x51A9BD: gfc_parse_file (parse.c:4297)
==14281==    by 0x557315: gfc_be_parse_file (f95-lang.c:250)
==14281==    by 0x909CDC: do_compile (toplev.c:557)
==14281==    by 0x90A853: toplev_main (toplev.c:2014)
==14281==    by 0x5712C4C: (below main) (libc-start.c:226)
==14281== 
==14281== Invalid read of size 8
==14281==    at 0x52869D: resolve_symbol (resolve.c:12726)
==14281==    by 0x545EF0: do_traverse_symtree (symbol.c:3386)
==14281==    by 0x532503: resolve_types (resolve.c:13859)
==14281==    by 0x527473: gfc_resolve (resolve.c:13959)
==14281==    by 0x528C18: resolve_symbol (resolve.c:12715)
==14281==    by 0x545EF0: do_traverse_symtree (symbol.c:3386)
==14281==    by 0x532503: resolve_types (resolve.c:13859)
==14281==    by 0x527473: gfc_resolve (resolve.c:13959)
==14281==    by 0x51ABBC: gfc_parse_file (parse.c:4594)
==14281==    by 0x557315: gfc_be_parse_file (f95-lang.c:250)
==14281==    by 0x909CDC: do_compile (toplev.c:557)
==14281==    by 0x90A853: toplev_main (toplev.c:2014)
==14281==  Address 0x5ca87e0 is 256 bytes inside a block of size 304 free'd
==14281==    at 0x4C270BD: free (vg_replace_malloc.c:366)
==14281==    by 0x546E91: gfc_undo_symbols (symbol.c:2898)
==14281==    by 0x514F5A: reject_statement (parse.c:1743)
==14281==    by 0x515A54: decode_statement (parse.c:316)
==14281==    by 0x516D8C: next_statement (parse.c:778)
==14281==    by 0x51801D: parse_spec (parse.c:2379)
==14281==    by 0x51A9BD: gfc_parse_file (parse.c:4297)
==14281==    by 0x557315: gfc_be_parse_file (f95-lang.c:250)
==14281==    by 0x909CDC: do_compile (toplev.c:557)
==14281==    by 0x90A853: toplev_main (toplev.c:2014)
==14281==    by 0x5712C4C: (below main) (libc-start.c:226)

So the problem seems to be that when we hit the error in the interface
declaration, we call gfc_undo_symbols() -> gfc_release_symbol() ->
gfc_free_symbol() -> free(), but then we go and dereference pointers to this
freed memory.

Unfortunately I'm not really familiar enough with this part of the codebase to
know how to fix it properly.