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* [gcc r12-8604] c++: function NTTP argument considered unused [PR53164, PR105848]
@ 2022-07-21 16:48 Patrick Palka
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From: Patrick Palka @ 2022-07-21 16:48 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:670ef5b108d0acfbde96f44b064079f2fa0c92d4
commit r12-8604-g670ef5b108d0acfbde96f44b064079f2fa0c92d4
Author: Patrick Palka <ppalka@redhat.com>
Date: Mon Jun 6 14:29:12 2022 -0400
c++: function NTTP argument considered unused [PR53164, PR105848]
Here at parse time the template argument f (an OVERLOAD) in A<f> gets
resolved ahead of time to the FUNCTION_DECL f<int>, and we defer marking
f<int> as used until instantiation (of g) as usual.
Later when instantiating g the type A<f> (where f has already been
resolved) is non-dependent, so tsubst_aggr_type avoids re-processing its
template arguments, and we end up never actually marking f<int> as used
(which means we never instantiate it) even though A<f>::h() later calls
it, leading to a link error.
This patch works around this issue by looking through ADDR_EXPR when
calling mark_used on the substituted callee of a CALL_EXPR.
PR c++/53164
PR c++/105848
gcc/cp/ChangeLog:
* pt.cc (tsubst_copy_and_build) <case CALL_EXPR>: Look through an
ADDR_EXPR callee when calling mark_used.
gcc/testsuite/ChangeLog:
* g++.dg/template/fn-ptr3.C: New test.
(cherry picked from commit 733a792a2b2e1662e738fa358b45a2720a8618a7)
Diff:
---
gcc/cp/pt.cc | 20 ++++++++++++++++----
gcc/testsuite/g++.dg/template/fn-ptr3.C | 28 ++++++++++++++++++++++++++++
2 files changed, 44 insertions(+), 4 deletions(-)
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index b2b1a5d1ec6..38c138bd835 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -20926,10 +20926,22 @@ tsubst_copy_and_build (tree t,
}
/* Remember that there was a reference to this entity. */
- if (function != NULL_TREE
- && DECL_P (function)
- && !mark_used (function, complain) && !(complain & tf_error))
- RETURN (error_mark_node);
+ if (function != NULL_TREE)
+ {
+ tree inner = function;
+ if (TREE_CODE (inner) == ADDR_EXPR
+ && TREE_CODE (TREE_OPERAND (inner, 0)) == FUNCTION_DECL)
+ /* We should already have called mark_used when taking the
+ address of this function, but do so again anyway to make
+ sure it's odr-used: at worst this is a no-op, but if we
+ obtained this FUNCTION_DECL as part of ahead-of-time overload
+ resolution then that call to mark_used wouldn't have marked it
+ odr-used yet (53164). */
+ inner = TREE_OPERAND (inner, 0);
+ if (DECL_P (inner)
+ && !mark_used (inner, complain) && !(complain & tf_error))
+ RETURN (error_mark_node);
+ }
if (!maybe_fold_fn_template_args (function, complain))
return error_mark_node;
diff --git a/gcc/testsuite/g++.dg/template/fn-ptr3.C b/gcc/testsuite/g++.dg/template/fn-ptr3.C
new file mode 100644
index 00000000000..4c651f124f6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/fn-ptr3.C
@@ -0,0 +1,28 @@
+// PR c++/53164
+// PR c++/105848
+// { dg-do link }
+
+template<class T>
+void f(T) { }
+
+template<void (*P)(int)>
+struct A {
+ static void wrap() {
+ P(0);
+ }
+};
+
+template<void (*P)(char)>
+void wrap() {
+ P(0);
+}
+
+template<int>
+void g() {
+ A<f>::wrap();
+ wrap<f>();
+}
+
+int main() {
+ g<0>();
+}
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