[patch] libguile GC crash

[Sam Hocevar]

   Hello, I am experiencing a crash using libguile 1.6.4. Here is a
reduced testcase: (crashes here for i = 1886, but YMMV)

#include <libguile.h>

int main(void) {
  char foo[128]; int i;
  scm_init_guile();
  for(i=0; i<100000; i++) {
    sprintf(foo, "symbol%i%i%i%i", i, i, i, i);
    scm_c_make_subr(foo, 0, NULL);
  }
  return 0;
}

   My understanding is that scm_c_make_subr() calls scm_must_realloc()
to reallocate new_table, which in turn calls check_mtrigger().  But when
a GC is triggered, scm_igc() calls scm_mark_subr_table(), and since the
memory pointed by new_table has just been realloc()ated but new_table
hasn't been updated yet, scm_mark_subr_table() crashes.

   A simple fix would be to call check_mtrigger() before realloc().
Proposed patch attached. I am not yet familiar with all the internals
so I may have missed something, but it looked pretty safe to me.

Regards,
-- 
Sam.

patch-guile-gc.diff
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