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.
/* 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);
+ {
+ /* Prevent GC. */
+ function_depth++;
+ synthesize_method (fn);
+ function_depth--;
+ }
return;
}
int processing_template_parmlist;
static int template_header_count;
-static GTY(()) tree saved_trees;
static vec<int> inline_parm_levels;
static GTY(()) struct tinst_level *current_tinst_level;
--- /dev/null
+// PR c++/99831
+// { dg-do compile { target c++20 } }
+// { dg-options "--param ggc-min-heapsize=0 --param ggc-min-expand=0" }
+
+template <int N> struct S {
+ constexpr S(const char (&str)[N]) : value{} { }
+ char value[N];
+};
+template <S> struct string {
+ constexpr bool operator==(const string &) const = default;
+};
+template <S L2> void operator+(string<L2>) {
+ char value[1];
+ S{value};
+}
+static_assert(string<"a">{} == string<"a">{});