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c++: lambda in template default argument [PR103186]

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The problem with this testcase was that since my patch for PR97900 we
weren't preserving DECL_UID identity for parameters of instantiations of
templated functions, so using those parameters as the keys for the
defarg_inst map broke.  I think this was always fragile given the
possibility of redeclarations, so instead of reverting that change let's
switch to keying off the function.

Memory use compiling stdc++.h is not noticeably different.

	PR c++/103186

gcc/cp/ChangeLog:

	* pt.cc (defarg_inst): Use tree_vec_map_cache_hasher.
	(defarg_insts_for): New.
	(tsubst_default_argument): Adjust.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/lambda/lambda-defarg10.C: New test.
This commit is contained in:
Jason Merrill 2022-01-26 16:42:57 -05:00
parent b649071d4b
commit 8a37897862
2 changed files with 54 additions and 9 deletions
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42
gcc/cp/pt.cc
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@ -13676,7 +13676,28 @@ tsubst_aggr_type (tree t,
}
}
static GTY((cache)) decl_tree_cache_map *defarg_inst;
/* Map from a FUNCTION_DECL to a vec of default argument instantiations,
indexed in reverse order of the parameters. */
static GTY((cache)) hash_table<tree_vec_map_cache_hasher> *defarg_inst;
/* Return a reference to the vec* of defarg insts for FN. */
static vec<tree,va_gc> *&
defarg_insts_for (tree fn)
{
if (!defarg_inst)
defarg_inst = hash_table<tree_vec_map_cache_hasher>::create_ggc (13);
tree_vec_map in = { fn, nullptr };
tree_vec_map **slot
= defarg_inst->find_slot_with_hash (&in, DECL_UID (fn), INSERT);
if (!*slot)
{
*slot = ggc_alloc<tree_vec_map> ();
**slot = in;
}
return (*slot)->to;
}
/* Substitute into the default argument ARG (a default argument for
FN), which has the indicated TYPE. */
@ -13706,9 +13727,16 @@ tsubst_default_argument (tree fn, int parmnum, tree type, tree arg,
gcc_assert (same_type_ignoring_top_level_qualifiers_p (type, parmtype));
tree *slot;
if (defarg_inst && (slot = defarg_inst->get (parm)))
return *slot;
/* Remember the location of the pointer to the vec rather than the location
of the particular element, in case the vec grows in tsubst_expr. */
vec<tree,va_gc> *&defs = defarg_insts_for (fn);
/* Index in reverse order to avoid allocating space for initial parameters
that don't have default arguments. */
unsigned ridx = list_length (parm);
if (vec_safe_length (defs) < ridx)
vec_safe_grow_cleared (defs, ridx);
else if (tree inst = (*defs)[ridx - 1])
return inst;
/* This default argument came from a template. Instantiate the
default argument here, not in tsubst. In the case of
@ -13753,11 +13781,7 @@ tsubst_default_argument (tree fn, int parmnum, tree type, tree arg,
pop_from_top_level ();
if (arg != error_mark_node && !cp_unevaluated_operand)
{
if (!defarg_inst)
defarg_inst = decl_tree_cache_map::create_ggc (37);
defarg_inst->put (parm, arg);
}
(*defs)[ridx - 1] = arg;
return arg;
}

21
gcc/testsuite/g++.dg/cpp0x/lambda/lambda-defarg10.C Normal file
View File

@ -0,0 +1,21 @@
// PR c++/103186
// { dg-do compile { target c++11 } }
struct f
{
template<class T1>
f(const T1&){}
};
template<typename T> class A {
public:
void foo(A<T> a, const f& fn = [](){}) { }
void bar(A<T> a) { foo(a); }
};
int main() {
A<int> a;
a.foo(a);
a.bar(a);
return 0;
}