[Bug modula2/101392] cc1gm2 -fdump-system-exports SEGV on Solaris/SPARC

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101392

Rainer Orth <ro at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2021-09-14
             Status|UNCONFIRMED                 |NEW

--- Comment #1 from Rainer Orth <ro at gcc dot gnu.org> ---
(In reply to Rainer Orth from comment #0)

> I couldn't make much sense of this yet.  Probably requires rebuilding cc1gm2
> with
> -g3 -O0.

I've now done just that.  Here's what I find:

Thread 2 received signal SIGSEGV, Segmentation fault.
[Switching to Thread 1 (LWP 1)]
0xfeb51bb0 in strlen () from /lib/libc.so.1
(gdb) where
#0  0xfeb51bb0 in strlen () from /lib/libc.so.1
#1  0xfeb937fc in strdup () from /lib/libc.so.1
#2  0x02a48c90 in lrealpath (filename=0x0)
    at /vol/gcc/src/git/modula-2/libiberty/lrealpath.c:88
#3  0x02a45fa4 in canonical_filename_eq (a=0xffbff8e2 "SYSTEM.s", b=0x0)
    at /vol/gcc/src/git/modula-2/libiberty/filename_cmp.c:216
#4  0x016e97c8 in init_asm_output (name=0x0)
    at /vol/gcc/src/git/modula-2/gcc/toplev.c:714
#5  0x016ed1dc in lang_dependent_init (name=0x0)
    at /vol/gcc/src/git/modula-2/gcc/toplev.c:1927
#6  0x016edf58 in do_compile () at /vol/gcc/src/git/modula-2/gcc/toplev.c:2218
#7  0x016ee4a8 in toplev::main (this=0xffbff6e2, argc=7, argv=0xffbff74c)
    at /vol/gcc/src/git/modula-2/gcc/toplev.c:2372
#8  0x02924ec4 in main (argc=7, argv=0xffbff74c)
    at /vol/gcc/src/git/modula-2/gcc/main.c:39

#4  0x016e97c8 in init_asm_output (name=0x0)
    at /vol/gcc/src/git/modula-2/gcc/toplev.c:714
714           else if (!canonical_filename_eq (asm_file_name, name)
(gdb) p asm_file_name
$3 = 0xffbff8e2 "SYSTEM.s"
(gdb) p name
$4 = 0x0
(gdb) up
#5  0x016ed1dc in lang_dependent_init (name=0x0)
    at /vol/gcc/src/git/modula-2/gcc/toplev.c:1927
1927          init_asm_output (name);
gdb) up
#6  0x016edf58 in do_compile () at /vol/gcc/src/git/modula-2/gcc/toplev.c:2218
2218          if (lang_dependent_init (main_input_filename))
(gdb) p main_input_filename
$6 = 0x0
(gdb) up
#7  0x016ee4a8 in toplev::main (this=0xffbff6e2, argc=7, argv=0xffbff74c)
    at /vol/gcc/src/git/modula-2/gcc/toplev.c:2372
2372          do_compile ();

Ultimately, the problem is two-fold:

* cc1gm2 doesn't set main_input_filename (perhaps only with
-fdump-system-exports,
  I haven't checked)
* In the end, libiberty's lrealpath is called with lrealpath (NULL, NULL)
  which again calls strdup (NULL), leading to the SEGV.  I couldn't find a
  clear indication if this is supported by the C standard, but even if I harden
  lrealpath to avoid strdup(NULL), I get more SEGVs later on in other places.

So clearly the error is not setting main_input_filename.  No idea why this
happens
for gm2 only or how to fix this, though.