[gcc r11-8201] c++: noexcept error recursion [PR100101]

[gcc r11-8201] c++: noexcept error recursion [PR100101]

[Jason Merrill]

https://gcc.gnu.org/g:2efbbba16a0630fac8cadcd6d9e0ffaabfadb79f

commit r11-8201-g2efbbba16a0630fac8cadcd6d9e0ffaabfadb79f
Author: Jason Merrill <jason@redhat.com>
Date:   Thu Apr 15 13:38:54 2021 -0400

    c++: noexcept error recursion [PR100101]
    
    Here instantiating the noexcept-specifier for bar<void>() means
    instantiating A<void>::value, which complains about the conversion from 0 to
    int* in the default argument of foo.  Since my patch for PR99583, printing
    the error context involves looking at C<void>::type, which again wants to
    instantiate A<void>::value, which breaks.  For now at least, let's break
    this recursion by avoiding looking into the noexcept-specifier in
    find_typenames, and limit that to just the uses_parameter_packs case that
    PR99583 cares about.
    
    gcc/cp/ChangeLog:
    
            PR c++/100101
            PR c++/99583
            * pt.c (find_parameter_packs_r) [FUNCTION_TYPE]: Walk into
            TYPE_RAISES_EXCEPTIONS here.
            * tree.c (cp_walk_subtrees): Not here.
    
    gcc/testsuite/ChangeLog:
    
            PR c++/100101
            * g++.dg/cpp0x/noexcept67.C: New test.

Diff:
---
 gcc/cp/pt.c                             | 11 +++++++++++
 gcc/cp/tree.c                           |  5 -----
 gcc/testsuite/g++.dg/cpp0x/noexcept67.C | 26 ++++++++++++++++++++++++++
 3 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 0f119a55272..2190f83882a 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -3890,6 +3890,10 @@ find_parameter_packs_r (tree *tp, int *walk_subtrees, void* data)
     (struct find_parameter_pack_data*)data;
   bool parameter_pack_p = false;
 
+#define WALK_SUBTREE(NODE)				\
+  cp_walk_tree (&(NODE), &find_parameter_packs_r,	\
+		ppd, ppd->visited)			\
+
   /* Don't look through typedefs; we are interested in whether a
      parameter pack is actually written in the expression/type we're
      looking at, not the target type.  */
@@ -4070,10 +4074,17 @@ find_parameter_packs_r (tree *tp, int *walk_subtrees, void* data)
 			ppd, ppd->visited);
       return NULL_TREE;
 
+    case FUNCTION_TYPE:
+    case METHOD_TYPE:
+      WALK_SUBTREE (TYPE_RAISES_EXCEPTIONS (t));
+      break;
+
     default:
       return NULL_TREE;
     }
 
+#undef WALK_SUBTREE
+
   return NULL_TREE;
 }
 
diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index 13cc61c3123..dca947bf52a 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -5415,11 +5415,6 @@ cp_walk_subtrees (tree *tp, int *walk_subtrees_p, walk_tree_fn func,
 	}
       break;
 
-    case FUNCTION_TYPE:
-    case METHOD_TYPE:
-      WALK_SUBTREE (TYPE_RAISES_EXCEPTIONS (*tp));
-      break;
-
     default:
       return NULL_TREE;
     }
diff --git a/gcc/testsuite/g++.dg/cpp0x/noexcept67.C b/gcc/testsuite/g++.dg/cpp0x/noexcept67.C
new file mode 100644
index 00000000000..7f061034323
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/noexcept67.C
@@ -0,0 +1,26 @@
+// PR c++/100101
+// { dg-do compile { target c++11 } }
+
+template <typename T> struct A
+{
+    template <typename U> static char foo(U*, int* = 0);
+    static const bool value = sizeof(foo(static_cast<T*>(nullptr))) > 0;
+};
+
+template <bool b> struct B
+{
+    static const bool value = b;
+};
+
+template <typename T> struct C
+{
+    typedef B<A<T>::value> type;
+};
+
+template <typename T>
+void bar() noexcept(A<T>::value && C<T>::type::value) {}
+
+void baz()
+{
+  bar<void>();
+}