[GRASS-dev] [grass-code I][509] v.mkgrid: segfault when "grid" parameters missing

Hamish hamish_nospam at yahoo.com
Thu Oct 11 06:53:05 EDT 2007

> code I item #509, was opened at 2007-10-11 10:29
> Summary: v.mkgrid: segfault when "grid" parameters missing 
> If the user fails to provide "grid" parameters, it segfaults. Applies to bot
> 6.2 CVS and 6.3 CVS. Example:
> $ v.mkgrid map=debug_grid position=region grid=
> Segmentation fault (core dumped)
> backtrace:
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 46912562415552 (LWP 26775)]
> 0x00002aaaabe92cf1 in __strtoull_internal () from /lib/libc.so.6
> (gdb) bt
> #0  0x00002aaaabe92cf1 in __strtoull_internal () from /lib/libc.so.6
> #1  0x00002aaaaba65022 in atoi () from /usr/local/lib/libgdal.so.1
> #2  0x0000000000401a25 in main (argc=4, argv=0x7fffff972dd8) at main.c:142

It is in the main.c atoi("") [line 137], but I'm not sure why it thinks that's
found in libgdal.

the root of the problem is that even though the option is declared
TYPE_INTEGER, that is never checked.
v.mkgrid/main.c has
  grid = G_define_option ();
  grid->key = "grid";
  grid->key_desc = "rows,columns";
  grid->type = TYPE_INTEGER;
  grid->required = YES;
  grid->multiple = NO;
  grid->description = _("Number of rows and columns in grid");

in lib/gis/parser.c  ~ line 2136 the check_opts() fn skips sending it to
check_an_opt() as (opt->options && opt->answer) are (null) and "" respectively.
[ie not allocated, and allocated but set to "\0" (?)]

it would be easy to add to v.mkgrid a test for the answer being empty and throw
it to {G_usage(); exit(EXIT_FAILURE);}, but that doesn't solve the general
problem- the parser should check for an integer answer. (same for TYPE_DOUBLE,
...) Note in this case the checker has to check key_desc to know to expect two
int answers.

G_parser() does catch the "grid=1," error with a please supply two values
message.  so maybe the problem is in check_multiple_opts()?

Interesting, I hadn't noticed the parser's custom opt->checker option-option


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