Fix SIGSEGV caused by dropped stack access from child process in gctest

(a cherry-pick of commit 673f0cf3f from 'master')

Issue #256 (bdwgc).

Previously, a local variable was passed in gctest to
GC_move_disappearing_link as a link to clear, this led to a memory
access violation during garbage collection in the child process
if the fork occurred between  GC_move_disappearing_link(..., &new_link)
and GC_unregister_disappearing_link(&new_link).

This commit changes the mentioned local variable (new_link) use - now
it contains a pointer to a heap-allocated link rather then containing
just a link.

* tests/test.c (mktree): Change type of new_link from void* to
void**; initialize it to GC_NEW(void*) and ensure it is non-null;
replace new_link with *new_link; add comment new_link object is
reclaimed correctly even if the thread is dropped in the child
process between GC_move_disappearing_link(new_link) and
GC_unregister_disappearing_link.

0 files changed, 0 insertions, 0 deletions