[GRASS-dev] [GRASS GIS] #1841: segmentation fault in v.patch

[GRASS GIS]

#1841: segmentation fault in v.patch
----------------------+-----------------------------------------------------
 Reporter:  pertusus  |       Owner:  grass-dev@…              
     Type:  defect    |      Status:  new                      
 Priority:  normal    |   Milestone:  7.0.0                    
Component:  Vector    |     Version:  svn-trunk                
 Keywords:            |    Platform:  Linux                    
      Cpu:  x86-64    |  
----------------------+-----------------------------------------------------
 A very simple v.patch segfaults. I tried to poke around in the code, and I
 found some leads, but I cannot really dig further. It is somewhat strange
 that nobody else stumbled on it.

 I attach a tarball to reproduce. Simply unpack, edit
 bug_v_patch.sh if you want to change the paths to grass, then run
 bug_v_patch.sh:
 {{{
 .....
 Writing attributes...
 ./bug_v_patch.sh: line 35: 32630 Segmentation fault      v.patch -e -a
 input=test_bug_v_patch_one output=test_bug_v_patch_two --o
 }}}

 I produced a backtrace from within the grass shell

 {{{
 > gdb --args v.patch -e -a input=test_bug_v_patch_one
 output=test_bug_v_patch_two --o
 (gdb) run
 ....
 Program received signal SIGSEGV, Segmentation fault.
 __strcpy_ssse3 () at ../sysdeps/x86_64/multiarch/strcpy.S:177
 177             movdqa  %xmm1, (%rdi)      /* store first 16 bytes into
 rdi */
 (gdb) bt
 #0  __strcpy_ssse3 () at ../sysdeps/x86_64/multiarch/strcpy.S:177
 #1  0x00007ffff79882de in set_string (x=0x7fffffffdd50, s=<value optimized
 out>, copy=<value optimized out>)
     at string.c:101
 #2  0x0000000000402d08 in main (argc=<value optimized out>, argv=<value
 optimized out>) at main.c:285
 (gdb)
 }}}

 trying to look at what happens

 {{{
 (gdb) break main.c:285
 Breakpoint 1 at 0x402cf7: file main.c, line 285.
 (gdb) run
 Breakpoint 1, main (argc=<value optimized out>, argv=<value optimized
 out>) at main.c:285
 285             db_set_string(&table_name_out, fi_out->table);
 (gdb) print table_name_out
 $1 = {string = 0x0, nalloc = 21}
 (gdb)
 }}}

 The string pointer maybe should not be NULL.

 Looking at what point it becomes null, by poking in gdb, I found that in
 fact the string is filled correctly at l 139, and if I set a breakpoint I
 can see its value. I set a new breakpoint at line 154, I can see that the
 string is set to null at that point (I also have a breakpoint l 156):
 {{{
 (gdb) break main.c:154
 Breakpoint 4 at 0x4029f9: file main.c, line 154.
 (gdb) run
 Breakpoint 4, main (argc=<value optimized out>, argv=<value optimized
 out>) at main.c:154
 154                 Vect_open_old_head(&InMap, in_name, "");
 (gdb) print table_name_out
 $3 = {string = 0x800ed0 "test_bug_v_patch_two", nalloc = 21}
 (gdb) n
 Breakpoint 2, main (argc=<value optimized out>, argv=<value optimized
 out>) at main.c:156
 156                 fi_in = Vect_get_field(&InMap, 1);
 (gdb) print table_name_out
 $4 = {string = 0x0, nalloc = 21}
 }}}

-- 
Ticket URL: <http://trac.osgeo.org/grass/ticket/1841>
GRASS GIS <http://grass.osgeo.org>