[Patch, fortran] PR20880 - Failure to detect procedures encompassing own interface

[Tobias Burnus]

Hi,

François-Xavier Coudert wrote:
> Take care that there is no reason for the backtrace of a sefault to
> actually point to the first corruption of memory. It is more often
> accurate to report the backtrace while running the programming with
> ElectricFence.
No ElectricFence run, but valgrind:

==16621== Invalid read of size 8
==16621==    at 0x459FDE: gfc_add_explicit_interface (symbol.c:1207)
==16621==    by 0x413B2E: gfc_match_formal_arglist (decl.c:2693)
==16621==    by 0x435C05: gfc_match_st_function (match.c:2937)
==16621==    by 0x441082: match_word (parse.c:65)
==16621==    by 0x441605: decode_statement (parse.c:132)
==16621==    by 0x44207A: next_statement (parse.c:499)
==16621==    by 0x443D70: parse_spec (parse.c:1536)
==16621==    by 0x444A99: gfc_parse_file (parse.c:3071)
==16621==    by 0x461CFD: gfc_be_parse_file (f95-lang.c:305)
==16621==    by 0x76A0E2: toplev_main (toplev.c:1033)
==16621==    by 0x52BAAE3: (below main) (in /lib64/libc-2.5.so)

This is symbol.c:

  1206
  1207    if (current_interface.ns)
  1208      {
  1209        if (current_interface.ns->proc_name) {
  1210          if (current_interface.ns->proc_name->name) {
  1211          if (sym->name) {
  1212          if (strcmp (current_interface.ns->proc_name->name,
sym->name) == 0) {
  1213        gfc_error ("'%s' at %L is the name of the enclosing
procedure",
  1214                   sym->name, where);
  1215        /* Return success so that redundant knock-on errors do not
occur.  */
  1216        return SUCCESS;
  1217        }}}}
  1218      }
  1219

Seemingly, current_interface.ns can be uninitialized and non zero.

"gfc_interface_info current_interface;" is defined in interface.c (and
as external in gfortran.h)
with gfc_namespace *ns.

It is set in "parse_interface()". The lines above from symbol.c are part
of gfc_add_explicit_interface(),
which is called in decl.c and parse.c.
As one can see from valgrind, it fails in gfc_match_formal_arglist

Tobias