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C++ PATCH for c++/85113, ICE with constexpr and __builtin_constant_p.
- From: Jason Merrill <jason at redhat dot com>
- To: gcc-patches List <gcc-patches at gcc dot gnu dot org>
- Date: Tue, 3 Apr 2018 15:12:31 -0400
- Subject: C++ PATCH for c++/85113, ICE with constexpr and __builtin_constant_p.
My recent patch to make sure that we've given an error for failed
template argument conversion caught this latent bug: when we evaluate
__builtin_constant_p within a constexpr function, we don't fold it
until later, at constexpr evaluation time when we have values for the
arguments. Which makes sense for the maybe_constant_value case. But
here we require a constant value, but are silently calling it
non-constant. So only do the deferral if we're being quiet about
non-constant expressions.
Tested x86_64-pc-linux-gnu, applying to trunk and 7.
commit be9bfa78348d2f5aec7209e126cf77ec89d60fc3
Author: Jason Merrill <jason@redhat.com>
Date: Tue Apr 3 13:59:29 2018 -0400
PR c++/85113 - ICE with constexpr and __builtin_constant_p.
* constexpr.c (cxx_eval_builtin_function_call): Only defer
__builtin_constant_p if ctx->quiet.
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index bebd9f5b5d0..201f27d8e66 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -1171,7 +1171,10 @@ cxx_eval_builtin_function_call (const constexpr_ctx *ctx, tree t, tree fun,
/* Don't fold __builtin_constant_p within a constexpr function. */
bool bi_const_p = (DECL_FUNCTION_CODE (fun) == BUILT_IN_CONSTANT_P);
+ /* If we aren't requiring a constant expression, defer __builtin_constant_p
+ in a constexpr function until we have values for the parameters. */
if (bi_const_p
+ && ctx->quiet
&& current_function_decl
&& DECL_DECLARED_CONSTEXPR_P (current_function_decl))
{
diff --git a/gcc/testsuite/g++.dg/ext/builtin12.C b/gcc/testsuite/g++.dg/ext/builtin12.C
new file mode 100644
index 00000000000..1d6bb75cd77
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/builtin12.C
@@ -0,0 +1,10 @@
+// PR c++/85113
+// { dg-do compile { target c++14 } }
+
+template<bool> struct A {};
+
+constexpr int foo()
+{
+ A<__builtin_constant_p(0)> a{};
+ return 0;
+}