Hi!
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.
The following patch implements the proposed wording of CWG 2552 in addition
to fixing the C++14 - C++20 handling bug.
If you'd like instead to keep the current pedantic C++23 wording for now,
that would mean taking out the first hunk (cxx_eval_constant_expression) and
g++.dg/cpp23/constexpr-nonlit2.C hunk.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk
(or ok without those 2 hunks for now)?
2022-03-22 Jakub Jelinek <ja...@redhat.com>
PR c++/104994
* constexpr.cc (cxx_eval_constant_expression): Don't diagnose passing
through extern thread_local declarations. Change wording from
declaration to definition.
(potential_constant_expression_1): Don't diagnose extern thread_local
declarations. Change wording from declared to defined.
* decl.cc (start_decl): Likewise.
* g++.dg/diagnostic/constexpr1.C: Change expected diagnostic wording
from declared to defined.
* g++.dg/cpp23/constexpr-nonlit1.C: Likewise.
(garply): Change dg-error into dg-bogus.
* g++.dg/cpp23/constexpr-nonlit2.C: Change expected diagnostic wording
from declaration to definition.
* g++.dg/cpp23/constexpr-nonlit6.C: Change expected diagnostic wording
from declared to defined.
* g++.dg/cpp23/constexpr-nonlit7.C: New test.
* g++.dg/cpp2a/constexpr-try5.C: Change expected diagnostic wording
from declared to defined.
* g++.dg/cpp2a/consteval3.C: Likewise.
--- gcc/cp/constexpr.cc.jj 2022-03-18 19:02:18.964688873 +0100
+++ gcc/cp/constexpr.cc 2022-03-21 15:52:09.000602363 +0100
@@ -6723,17 +6723,18 @@ cxx_eval_constant_expression (const cons
}
if (VAR_P (r)
- && (TREE_STATIC (r) || CP_DECL_THREAD_LOCAL_P (r))
+ && (TREE_STATIC (r)
+ || (CP_DECL_THREAD_LOCAL_P (r) && !DECL_REALLY_EXTERN (r)))
/* Allow __FUNCTION__ etc. */
&& !DECL_ARTIFICIAL (r))
{
if (!ctx->quiet)
{
if (CP_DECL_THREAD_LOCAL_P (r))
- error_at (loc, "control passes through declaration of %qD "
+ error_at (loc, "control passes through definition of %qD "
"with thread storage duration", r);
else
- error_at (loc, "control passes through declaration of %qD "
+ error_at (loc, "control passes through definition of %qD "
"with static storage duration", r);
}
*non_constant_p = true;
@@ -9188,17 +9189,17 @@ potential_constant_expression_1 (tree t,
tmp = DECL_EXPR_DECL (t);
if (VAR_P (tmp) && !DECL_ARTIFICIAL (tmp))
{
- if (CP_DECL_THREAD_LOCAL_P (tmp))
+ if (CP_DECL_THREAD_LOCAL_P (tmp) && !DECL_REALLY_EXTERN (tmp))
{
if (flags & tf_error)
- error_at (DECL_SOURCE_LOCATION (tmp), "%qD declared "
+ error_at (DECL_SOURCE_LOCATION (tmp), "%qD defined "
"%<thread_local%> in %<constexpr%> context", tmp);
return false;
}
else if (TREE_STATIC (tmp))
{
if (flags & tf_error)
- error_at (DECL_SOURCE_LOCATION (tmp), "%qD declared "
+ error_at (DECL_SOURCE_LOCATION (tmp), "%qD defined "
"%<static%> in %<constexpr%> context", tmp);
return false;
}
--- gcc/cp/decl.cc.jj 2022-03-14 10:34:34.246922669 +0100
+++ gcc/cp/decl.cc 2022-03-21 15:51:17.053317191 +0100
@@ -5774,15 +5774,15 @@ start_decl (const cp_declarator *declara
&& cxx_dialect < cxx23)
{
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 only "
+ "%qD defined %<thread_local%> in %qs function only "
"available with %<-std=c++2b%> or %<-std=gnu++2b%>", decl,
DECL_IMMEDIATE_FUNCTION_P (current_function_decl)
? "consteval" : "constexpr");
else if (TREE_STATIC (decl))
error_at (DECL_SOURCE_LOCATION (decl),
- "%qD declared %<static%> in %qs function only available "
+ "%qD defined %<static%> in %qs function only available "
"with %<-std=c++2b%> or %<-std=gnu++2b%>", decl,
DECL_IMMEDIATE_FUNCTION_P (current_function_decl)
? "consteval" : "constexpr");
--- gcc/testsuite/g++.dg/diagnostic/constexpr1.C.jj 2021-12-30
15:12:43.263149870 +0100
+++ gcc/testsuite/g++.dg/diagnostic/constexpr1.C 2022-03-21
16:02:53.017740314 +0100
@@ -1,7 +1,7 @@
// { dg-do compile { target c++11 } }
-constexpr int foo() { thread_local int i __attribute__((unused)) {}; return 1;
} // { dg-error "40:.i. declared .thread_local." "" { target c++20_down } }
-// { dg-error "40:.i. declared .thread_local. in .constexpr. context" "" {
target c++23 } .-1 }
+constexpr int foo() { thread_local int i __attribute__((unused)) {}; return 1;
} // { dg-error "40:.i. defined .thread_local." "" { target c++20_down } }
+// { dg-error "40:.i. defined .thread_local. in .constexpr. context" "" {
target c++23 } .-1 }
-constexpr int bar() { static int i __attribute__((unused)) {}; return 1; } //
{ dg-error "34:.i. declared .static." "" { target c++20_down } }
-// { dg-error "34:.i. declared .static. in .constexpr. context" "" { target
c++23 } .-1 }
+constexpr int bar() { static int i __attribute__((unused)) {}; return 1; } //
{ dg-error "34:.i. defined .static." "" { target c++20_down } }
+// { dg-error "34:.i. defined .static. in .constexpr. context" "" { target
c++23 } .-1 }
--- gcc/testsuite/g++.dg/cpp23/constexpr-nonlit1.C.jj 2021-12-30
15:12:43.260149912 +0100
+++ gcc/testsuite/g++.dg/cpp23/constexpr-nonlit1.C 2022-03-21
15:30:09.210796311 +0100
@@ -23,7 +23,7 @@ baz (int x)
{
if (!x)
return 1;
- static int a; // { dg-error "'a' declared 'static' in 'constexpr'
function only available with" "" { target c++20_down } }
+ static int a; // { dg-error "'a' defined 'static' in 'constexpr'
function only available with" "" { target c++20_down } }
return ++a; // { dg-error "uninitialized variable 'a' in 'constexpr'
function" "" { target c++17_down } .-1 }
}
@@ -32,7 +32,7 @@ qux (int x)
{
if (!x)
return 1;
- thread_local int a; // { dg-error "'a' declared 'thread_local' in
'constexpr' function only available with" "" { target c++20_down } }
+ thread_local int a; // { dg-error "'a' defined 'thread_local' in
'constexpr' function only available with" "" { target c++20_down } }
return ++a; // { dg-error "uninitialized variable 'a' in 'constexpr'
function" "" { target c++17_down } .-1 }
}
@@ -41,7 +41,7 @@ garply (int x)
{
if (!x)
return 1;
- extern thread_local int a; // { dg-error "'a' declared 'thread_local' in
'constexpr' function only available with" "" { target c++20_down } }
+ extern thread_local int a; // { dg-bogus "'thread_local' in 'constexpr'
function only available with" "" { target c++20_down } }
return ++a;
}
--- gcc/testsuite/g++.dg/cpp23/constexpr-nonlit2.C.jj 2021-12-30
15:12:43.260149912 +0100
+++ gcc/testsuite/g++.dg/cpp23/constexpr-nonlit2.C 2022-03-21
15:30:41.759347320 +0100
@@ -24,7 +24,7 @@ baz (int x)
{
if (!x)
return 1;
- static int a; // { dg-error "control passes through
declaration of 'a' with static storage duration" }
+ static int a; // { dg-error "control passes through
definition of 'a' with static storage duration" }
return ++a;
}
@@ -33,7 +33,7 @@ qux (int x)
{
if (!x)
return 1;
- thread_local int a; // { dg-error "control passes through declaration of
'a' with thread storage duration" }
+ thread_local int a; // { dg-error "control passes through definition of 'a'
with thread storage duration" }
return ++a;
}
--- gcc/testsuite/g++.dg/cpp23/constexpr-nonlit6.C.jj 2021-12-30
15:12:43.260149912 +0100
+++ gcc/testsuite/g++.dg/cpp23/constexpr-nonlit6.C 2022-03-21
15:36:56.993172539 +0100
@@ -13,13 +13,13 @@ lab:
constexpr int
bar ()
{
- static int a; // { dg-error "'a' declared 'static' in
'constexpr' context" }
+ static int a; // { dg-error "'a' defined 'static' in
'constexpr' context" }
return ++a;
}
constexpr int
baz (int x)
{
- thread_local int a; // { dg-error "'a' declared 'thread_local' in
'constexpr' context" }
+ thread_local int a; // { dg-error "'a' defined 'thread_local' in
'constexpr' context" }
return ++a;
}
--- gcc/testsuite/g++.dg/cpp23/constexpr-nonlit7.C.jj 2022-03-21
16:05:28.992594010 +0100
+++ gcc/testsuite/g++.dg/cpp23/constexpr-nonlit7.C 2022-03-21
16:20:06.291535273 +0100
@@ -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 ();
--- gcc/testsuite/g++.dg/cpp2a/constexpr-try5.C.jj 2021-12-30
15:12:43.262149884 +0100
+++ gcc/testsuite/g++.dg/cpp2a/constexpr-try5.C 2022-03-21 16:02:07.512366493
+0100
@@ -5,14 +5,14 @@
constexpr int foo ()
try { // { dg-warning "function-try-block body of 'constexpr'
function only available with" "" { target c++17_down } }
int a; // { dg-error "uninitialized variable 'a' in
'constexpr' function" "" { target c++17_down } }
- static double b = 1.0;// { dg-error "'b' declared 'static' in 'constexpr'
function only available with" "" { target c++20_down } }
- // { dg-error "'b' declared 'static' in 'constexpr'
context" "" { target c++23 } .-1 }
+ static double b = 1.0;// { dg-error "'b' defined 'static' in 'constexpr'
function only available with" "" { target c++20_down } }
+ // { dg-error "'b' defined 'static' in 'constexpr'
context" "" { target c++23 } .-1 }
goto l; // { dg-error "'goto' in 'constexpr' function only
available with" "" { target c++20_down } }
l:;
return 0;
} catch (...) {
long int c; // { dg-error "uninitialized variable 'c' in
'constexpr' function" "" { target c++17_down } }
- static float d = 2.0f;// { dg-error "'d' declared 'static' in 'constexpr'
function only available with" "" { target c++20_down } }
+ static float d = 2.0f;// { dg-error "'d' defined 'static' in 'constexpr'
function only available with" "" { target c++20_down } }
goto l2; // { dg-error "'goto' in 'constexpr' function only
available with" "" { target c++20_down } }
l2:;
return -1;
@@ -21,20 +21,20 @@ try { // { dg-warning "function-try-bl
constexpr int bar ()
{
int a; // { dg-error "uninitialized variable 'a' in
'constexpr' function" "" { target c++17_down } }
- static long double b = 3.0;// { dg-error "'b' declared 'static' in
'constexpr' function only available with" "" { target c++20_down } }
- // { dg-error "'b' declared 'static' in 'constexpr'
context" "" { target c++23 } .-1 }
+ static long double b = 3.0;// { dg-error "'b' defined 'static' in
'constexpr' function only available with" "" { target c++20_down } }
+ // { dg-error "'b' defined 'static' in 'constexpr'
context" "" { target c++23 } .-1 }
goto l; // { dg-error "'goto' in 'constexpr' function only
available with" "" { target c++20_down } }
l:;
try { // { dg-warning "'try' in 'constexpr' function
only available with" "" { target c++17_down } }
short c; // { dg-error "uninitialized variable 'c' in
'constexpr' function" "" { target c++17_down } }
- static float d; // { dg-error "'d' declared 'static' in 'constexpr'
function only available with" "" { target c++20_down } }
+ static float d; // { dg-error "'d' defined 'static' in 'constexpr'
function only available with" "" { target c++20_down } }
// { dg-error "uninitialized variable 'd' in
'constexpr' function" "" { target c++17_down } .-1 }
goto l2; // { dg-error "'goto' in 'constexpr' function only
available with" "" { target c++20_down } }
l2:;
return 0;
} catch (int) {
char e; // { dg-error "uninitialized variable 'e' in
'constexpr' function" "" { target c++17_down } }
- static int f = 5; // { dg-error "'f' declared 'static' in 'constexpr'
function only available with" "" { target c++20_down } }
+ static int f = 5; // { dg-error "'f' defined 'static' in 'constexpr'
function only available with" "" { target c++20_down } }
goto l3; // { dg-error "'goto' in 'constexpr' function only
available with" "" { target c++20_down } }
l3:;
return 1;
--- gcc/testsuite/g++.dg/cpp2a/consteval3.C.jj 2021-12-30 15:12:43.262149884
+0100
+++ gcc/testsuite/g++.dg/cpp2a/consteval3.C 2022-03-21 16:01:26.477931150
+0100
@@ -56,8 +56,8 @@ template consteval float f12 (float x);
consteval int
f13 (int x)
{
- static int a = 5; // { dg-error "'a' declared 'static' in
'consteval' function only available with" "" { target c++20_only } }
- // { dg-error "'a' declared 'static' in
'constexpr' context" "" { target c++23 } .-1 }
- thread_local int b = 6; // { dg-error "'b' declared 'thread_local' in
'consteval' function only available with" "" { target c++20_only } }
+ static int a = 5; // { dg-error "'a' defined 'static' in
'consteval' function only available with" "" { target c++20_only } }
+ // { dg-error "'a' defined 'static' in
'constexpr' context" "" { target c++23 } .-1 }
+ thread_local int b = 6; // { dg-error "'b' defined 'thread_local' in
'consteval' function only available with" "" { target c++20_only } }
return x;
}
Jakub
