This issue had to do with us bailing out too soon when trying to
mark_used a constant variable in an unevaluated context. I fixed this
for 4.6 as part of the constexpr work, but a subset of that patch seems
suitable for backporting.
Tested x86_64-pc-linux-gnu, applying to 4.4 and 4.5.
commit fc071e935530d226d24e08c25e5f66b0c61f0654
Author: Jason Merrill <ja...@redhat.com>
Date: Mon May 9 09:42:17 2011 -0400
PR c++/48936
* decl2.c (mark_used): Instantiate constant variables even
in unevaluated context.
diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index d27ed43..6c33434 100644
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -3991,8 +3991,6 @@ possibly_inlined_p (tree decl)
void
mark_used (tree decl)
{
- HOST_WIDE_INT saved_processing_template_decl = 0;
-
/* If DECL is a BASELINK for a single function, then treat it just
like the DECL for the function. Otherwise, if the BASELINK is
for an overloaded function, we don't know which function was
@@ -4029,9 +4027,6 @@ mark_used (tree decl)
error ("used here");
return;
}
- /* If we don't need a value, then we don't need to synthesize DECL. */
- if (cp_unevaluated_operand != 0)
- return;
/* We can only check DECL_ODR_USED on variables or functions with
DECL_LANG_SPECIFIC set, and these are also the only decls that we
@@ -4059,9 +4054,10 @@ mark_used (tree decl)
DECL. However, if DECL is a static data member initialized with
a constant, we need the value right now because a reference to
such a data member is not value-dependent. */
- if (TREE_CODE (decl) == VAR_DECL
- && DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (decl)
- && DECL_CLASS_SCOPE_P (decl))
+ if (DECL_INTEGRAL_CONSTANT_VAR_P (decl)
+ && !DECL_INITIAL (decl)
+ && DECL_LANG_SPECIFIC (decl)
+ && DECL_TEMPLATE_INSTANTIATION (decl))
{
/* Don't try to instantiate members of dependent types. We
cannot just use dependent_type_p here because this function
@@ -4071,12 +4067,14 @@ mark_used (tree decl)
if (CLASSTYPE_TEMPLATE_INFO ((DECL_CONTEXT (decl)))
&& uses_template_parms (CLASSTYPE_TI_ARGS (DECL_CONTEXT (decl))))
return;
- /* Pretend that we are not in a template, even if we are, so
- that the static data member initializer will be processed. */
- saved_processing_template_decl = processing_template_decl;
- processing_template_decl = 0;
+ instantiate_decl (decl, /*defer_ok=*/false,
+ /*expl_inst_class_mem_p=*/false);
}
+ /* If we don't need a value, then we don't need to synthesize DECL. */
+ if (cp_unevaluated_operand != 0)
+ return;
+
if (processing_template_decl)
return;
@@ -4149,8 +4147,6 @@ mark_used (tree decl)
need. Therefore, we always try to defer instantiation. */
instantiate_decl (decl, /*defer_ok=*/true,
/*expl_inst_class_mem_p=*/false);
-
- processing_template_decl = saved_processing_template_decl;
}
#include "gt-cp-decl2.h"
diff --git a/gcc/testsuite/g++.dg/template/nontype23.C
b/gcc/testsuite/g++.dg/template/nontype23.C
new file mode 100644
index 0000000..dfda4fe
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/nontype23.C
@@ -0,0 +1,9 @@
+// PR c++/48936
+
+template <bool C> int foo (void);
+template <class T> struct S
+{
+ static const unsigned int a = sizeof (T);
+ enum { c = sizeof (foo <(a == 0)> ()) };
+};
+S<int> x;
