Ubuntu
gcc-4.7 package

  1. Quantal (12.10)
  2. Bug #1065559
  3. Comment #8

Comment 8 for bug 1065559

Revision history for this message
In , Zhenqiang Chen (zhenqiang-chen) wrote :

Created attachment 28512
gdb backtrace

Root cause:

PRE bases on the result of value numbering (run_scc_vn). At the end, it free_scc_vn. But before free_scc_vn, it might call cleanup_tree_cfg ();

  if (do_eh_cleanup || do_ab_cleanup)
    cleanup_tree_cfg ();

cleanup_tree_cfg might call make_ssa_name which might reuse some "name" from the FREE_SSANAMES list. If the VN_INFO of the "name" is NULL, free_scc_vn will "Segmentation fault".

Richard's patch makes "do_eh_cleanup" to false. So cleanup_tree_cfg is not called in PRE. Then no new ssa name will be created.

bt.log shows the gdb backtrace to create a new ssa name.