https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99831
--- Comment #13 from CVS Commits ---
The releases/gcc-10 branch has been updated by Marek Polacek
:
https://gcc.gnu.org/g:3252b78f7ef7847b109e7b43daf7ca1a6f0d6fab
commit r10-9689-g3252b78f7ef7847b109e7b43daf7ca1a6f0d6fab
Author: Marek Polacek
Date: Thu Apr 1 10:42:43 2021 -0400
c++: GC collects live data when synthesizing operator== [PR99831]
Here we crash in reshape_init because we're accessing ggc_freed
& poisoned data: since r277865 in defaulted_late_check we call
synthesize_method here:
if (kind == sfk_comparison)
{
/* If the function was declared constexpr, check that the definition
qualifies. Otherwise we can define the function lazily. */
if (DECL_DECLARED_CONSTEXPR_P (fn) && !DECL_INITIAL (fn))
synthesize_method (fn);
return;
}
which in this test triggers when we're processing the string<"a">{} in
the static_assert. First, we create a CONSTRUCTOR for the "{}" in
cp_parser_functional_cast, then we call finish_compound_literal which
calls complete_type and that results in garbage collection, which then
frees the CONSTRUCTOR {} we created when parsing the braced-list in
string<"a">{} -- at this point, it's not referenced by anything.
(That's not the case for 'type' in finish_compound_literal: the symbol
table contains a node for operator==, so ggc_mark_roots goes and marks
the fn decl, its type, its arguments etc., as used, so we don't collect
it.)
We could just bump function_depth around the new call to synthesize_method
to prevent GC.
gcc/cp/ChangeLog:
PR c++/99831
* method.c (defaulted_late_check): ++ and -- function_depth around
the call to synthesize_method.
* pt.c: Remove the saved_trees global.
gcc/testsuite/ChangeLog:
PR c++/99831
* g++.dg/other/gc6.C: New test.
(cherry picked from commit 6a60ffc297b9d4903543a25538e62e7fb39420a9)
