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* [gcc r10-10698] c++: extern thread_local declarations in constexpr [PR104994]
@ 2022-05-10 8:25 Jakub Jelinek
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From: Jakub Jelinek @ 2022-05-10 8:25 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:125234a3b78138e22112bb3f207df987817b6818
commit r10-10698-g125234a3b78138e22112bb3f207df987817b6818
Author: Jakub Jelinek <jakub@redhat.com>
Date: Thu Mar 24 10:12:25 2022 +0100
c++: extern thread_local declarations in constexpr [PR104994]
C++14 to C++20 apparently should allow extern thread_local declarations in
constexpr functions, however useless they are there (because accessing
such vars is not valid in a constant expression, perhaps sizeof/decltype).
P2242 changed that for C++23 to passing through declaration but
https://cplusplus.github.io/CWG/issues/2552.html
has been filed for it yesterday.
2022-03-24 Jakub Jelinek <jakub@redhat.com>
PR c++/104994
* constexpr.c (potential_constant_expression_1): Don't diagnose extern
thread_local declarations.
* decl.c (start_decl): Likewise.
* g++.dg/cpp2a/constexpr-nonlit7.C: New test.
(cherry picked from commit 72124f487ccb5c8065dd5f7b8fba254600b7e611)
Diff:
---
gcc/cp/constexpr.c | 8 ++++----
gcc/cp/decl.c | 2 +-
gcc/testsuite/g++.dg/cpp2a/constexpr-nonlit7.C | 6 ++++++
3 files changed, 11 insertions(+), 5 deletions(-)
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 8e193edeff8..dd0e955ed7b 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -8297,18 +8297,18 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now,
tmp = DECL_EXPR_DECL (t);
if (VAR_P (tmp) && !DECL_ARTIFICIAL (tmp))
{
- if (TREE_STATIC (tmp))
+ if (CP_DECL_THREAD_LOCAL_P (tmp) && !DECL_REALLY_EXTERN (tmp))
{
if (flags & tf_error)
error_at (DECL_SOURCE_LOCATION (tmp), "%qD declared "
- "%<static%> in %<constexpr%> context", tmp);
+ "%<thread_local%> in %<constexpr%> context", tmp);
return false;
}
- else if (CP_DECL_THREAD_LOCAL_P (tmp))
+ else if (TREE_STATIC (tmp))
{
if (flags & tf_error)
error_at (DECL_SOURCE_LOCATION (tmp), "%qD declared "
- "%<thread_local%> in %<constexpr%> context", tmp);
+ "%<static%> in %<constexpr%> context", tmp);
return false;
}
else if (!check_for_uninitialized_const_var
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 47dc43177ef..e923fb0fe13 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -5447,7 +5447,7 @@ start_decl (const cp_declarator *declarator,
&& DECL_DECLARED_CONSTEXPR_P (current_function_decl))
{
bool ok = false;
- if (CP_DECL_THREAD_LOCAL_P (decl))
+ if (CP_DECL_THREAD_LOCAL_P (decl) && !DECL_REALLY_EXTERN (decl))
error_at (DECL_SOURCE_LOCATION (decl),
"%qD declared %<thread_local%> in %qs function", decl,
DECL_IMMEDIATE_FUNCTION_P (current_function_decl)
diff --git a/gcc/testsuite/g++.dg/cpp2a/constexpr-nonlit7.C b/gcc/testsuite/g++.dg/cpp2a/constexpr-nonlit7.C
new file mode 100644
index 00000000000..06125756f25
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/constexpr-nonlit7.C
@@ -0,0 +1,6 @@
+// PR c++/104994
+// CWG2552
+// { dg-do compile { target c++14 } }
+
+constexpr bool foo () { extern thread_local int t; return true; }
+static constexpr bool a = foo ();
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