https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98126
--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Marek Polacek <mpola...@gcc.gnu.org>: https://gcc.gnu.org/g:1cac89da2cb1f2a7c2d93f7f325484c2d1619ca8 commit r11-5826-g1cac89da2cb1f2a7c2d93f7f325484c2d1619ca8 Author: Marek Polacek <pola...@redhat.com> Date: Thu Dec 3 18:35:00 2020 -0500 c-family: Fix hang with -Wsequence-point [PR98126] verify_sequence_points uses verify_tree to recursively walk the subexpressions of an expression, and while recursing, it also keeps lists of expressions found after/before a sequence point. For a large expression, the list can grow significantly. And merge_tlist is at least N(n^2): for a list of length n it will iterate n(n -1) times, and call candidate_equal_p each time, and that can recurse further. warn_for_collision also has to go through the whole list. With a large-enough expression, the compilation can easily get stuck here for 24 hours. This patch is a simple kludge: if we see that the expression is overly complex, don't even try. gcc/c-family/ChangeLog: PR c++/98126 * c-common.c (verify_tree_lim_r): New function. (verify_sequence_points): Use it. Use nullptr instead of 0. gcc/testsuite/ChangeLog: PR c++/98126 * g++.dg/warn/Wsequence-point-4.C: New test.
