https://gcc.gnu.org/g:292fc21a8d7aa2f16e61ac941e22ada6ddd85500
commit r15-762-g292fc21a8d7aa2f16e61ac941e22ada6ddd85500
Author: Nathaniel Shead <nathanielosh...@gmail.com>
Date: Sat May 11 22:25:44 2024 +1000
c++: Strengthen checks on 'main'
This patch adds some missing requirements for legal main declarations,
as according to [basic.start.main] p2.
gcc/cp/ChangeLog:
* decl.cc (grokfndecl): Check for main functions with language
linkage or module attachment.
(grokvardecl): Check for extern 'C' entities named main.
gcc/testsuite/ChangeLog:
* g++.dg/abi/main.C: Check pedwarn for main with linkage-spec.
* g++.dg/modules/contracts-1_b.C: Don't declare main in named
module.
* g++.dg/modules/contracts-3_b.C: Likewise.
* g++.dg/modules/contracts-4_d.C: Likewise.
* g++.dg/modules/horcrux-1_a.C: Export declarations, so that...
* g++.dg/modules/horcrux-1_b.C: Don't declare main in named
module.
* g++.dg/modules/main-1.C: New test.
* g++.dg/parse/linkage5.C: New test.
* g++.dg/parse/linkage6.C: New test.
Signed-off-by: Nathaniel Shead <nathanielosh...@gmail.com>
Diff:
---
gcc/cp/decl.cc | 19 +++++++++++++++----
gcc/testsuite/g++.dg/abi/main.C | 3 ++-
gcc/testsuite/g++.dg/modules/contracts-1_b.C | 4 ----
gcc/testsuite/g++.dg/modules/contracts-3_b.C | 4 ----
gcc/testsuite/g++.dg/modules/contracts-4_d.C | 2 --
gcc/testsuite/g++.dg/modules/horcrux-1_a.C | 3 +++
gcc/testsuite/g++.dg/modules/horcrux-1_b.C | 2 +-
gcc/testsuite/g++.dg/modules/main-1.C | 5 +++++
gcc/testsuite/g++.dg/parse/linkage5.C | 14 ++++++++++++++
gcc/testsuite/g++.dg/parse/linkage6.C | 13 +++++++++++++
10 files changed, 53 insertions(+), 16 deletions(-)
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 6fcab615d55..a992d54dc8f 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -10788,6 +10788,11 @@ grokfndecl (tree ctype,
"cannot declare %<::main%> to be %qs", "consteval");
if (!publicp)
error_at (location, "cannot declare %<::main%> to be static");
+ if (current_lang_depth () != 0)
+ pedwarn (location, OPT_Wpedantic, "cannot declare %<::main%> with a"
+ " linkage specification");
+ if (module_attach_p ())
+ error_at (location, "cannot attach %<::main%> to a named module");
inlinep = 0;
publicp = 1;
}
@@ -11287,10 +11292,16 @@ grokvardecl (tree type,
DECL_INTERFACE_KNOWN (decl) = 1;
if (DECL_NAME (decl)
- && MAIN_NAME_P (DECL_NAME (decl))
- && scope == global_namespace)
- error_at (DECL_SOURCE_LOCATION (decl),
- "cannot declare %<::main%> to be a global variable");
+ && MAIN_NAME_P (DECL_NAME (decl)))
+ {
+ if (scope == global_namespace)
+ error_at (DECL_SOURCE_LOCATION (decl),
+ "cannot declare %<::main%> to be a global variable");
+ else if (DECL_EXTERN_C_P (decl))
+ error_at (DECL_SOURCE_LOCATION (decl),
+ "an entity named %<main%> cannot be declared with "
+ "C language linkage");
+ }
/* Check that the variable can be safely declared as a concept.
Note that this also forbids explicit specializations. */
diff --git a/gcc/testsuite/g++.dg/abi/main.C b/gcc/testsuite/g++.dg/abi/main.C
index 4c5f1ea213c..2797a16df5b 100644
--- a/gcc/testsuite/g++.dg/abi/main.C
+++ b/gcc/testsuite/g++.dg/abi/main.C
@@ -1,10 +1,11 @@
/* { dg-do compile } */
+/* { dg-additional-options "-Wno-error=pedantic" }
/* Check if entry points get implicit C linkage. If they don't, compiler will
* error on incompatible declarations */
int main();
-extern "C" int main();
+extern "C" int main(); // { dg-warning "linkage specification" }
#ifdef __MINGW32__
diff --git a/gcc/testsuite/g++.dg/modules/contracts-1_b.C
b/gcc/testsuite/g++.dg/modules/contracts-1_b.C
index 30c15f6928b..aa36c8d6b1b 100644
--- a/gcc/testsuite/g++.dg/modules/contracts-1_b.C
+++ b/gcc/testsuite/g++.dg/modules/contracts-1_b.C
@@ -1,15 +1,11 @@
// { dg-module-do run }
// { dg-additional-options "-fmodules-ts -fcontracts
-fcontract-continuation-mode=on" }
-module;
#include <cstdio>
-export module bar;
-// { dg-module-cmi bar }
import foo;
template<typename T>
bool bar_fn_pre(T n) { printf("bar fn pre(%d)\n", n); return true; }
-export
template<typename T>
T bar_fn(T n)
[[ pre: bar_fn_pre(n) && n > 0 ]]
diff --git a/gcc/testsuite/g++.dg/modules/contracts-3_b.C
b/gcc/testsuite/g++.dg/modules/contracts-3_b.C
index b1d6375391b..1a29e2c3e5d 100644
--- a/gcc/testsuite/g++.dg/modules/contracts-3_b.C
+++ b/gcc/testsuite/g++.dg/modules/contracts-3_b.C
@@ -1,15 +1,11 @@
// { dg-module-do run }
// { dg-additional-options "-fmodules-ts -fcontracts
-fcontract-role=default:ignore,ignore,ignore" }
-module;
#include <cstdio>
-export module bar;
-// { dg-module-cmi bar }
import foo;
template<typename T>
bool bar_fn_pre(T n) { printf("bar fn pre(%d)\n", n); return true; }
-export
template<typename T>
T bar_fn(T n)
[[ pre: bar_fn_pre(n) && n > 0 ]]
diff --git a/gcc/testsuite/g++.dg/modules/contracts-4_d.C
b/gcc/testsuite/g++.dg/modules/contracts-4_d.C
index dc56251d1d8..9e6b7c3d4de 100644
--- a/gcc/testsuite/g++.dg/modules/contracts-4_d.C
+++ b/gcc/testsuite/g++.dg/modules/contracts-4_d.C
@@ -1,8 +1,6 @@
// { dg-module-do run }
// { dg-additional-options "-fmodules-ts -fcontracts" }
-module;
#include <cstdio>
-export module baz;
import foo;
import bar;
diff --git a/gcc/testsuite/g++.dg/modules/horcrux-1_a.C
b/gcc/testsuite/g++.dg/modules/horcrux-1_a.C
index ff548d039ea..c115bd2965b 100644
--- a/gcc/testsuite/g++.dg/modules/horcrux-1_a.C
+++ b/gcc/testsuite/g++.dg/modules/horcrux-1_a.C
@@ -3,13 +3,16 @@
export module foo;
// { dg-module-cmi foo }
+export
template<typename _Tp, _Tp __v>
struct integral_constant
{};
+export
template<bool __v>
using __bool_constant = integral_constant<bool, __v>;
+export
template<typename _Tp, typename... _Args>
struct __is_constructible_impl
: public __bool_constant<__is_constructible(_Tp, _Args...)>
diff --git a/gcc/testsuite/g++.dg/modules/horcrux-1_b.C
b/gcc/testsuite/g++.dg/modules/horcrux-1_b.C
index 842bf413585..54aa069436a 100644
--- a/gcc/testsuite/g++.dg/modules/horcrux-1_b.C
+++ b/gcc/testsuite/g++.dg/modules/horcrux-1_b.C
@@ -1,6 +1,6 @@
// { dg-additional-options -fmodules-ts }
-module foo;
+import foo;
int main ()
{
diff --git a/gcc/testsuite/g++.dg/modules/main-1.C
b/gcc/testsuite/g++.dg/modules/main-1.C
new file mode 100644
index 00000000000..0d79edddb75
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/main-1.C
@@ -0,0 +1,5 @@
+// { dg-additional-options "-fmodules-ts" }
+// { dg-prune-output "not writing module" }
+
+export module M;
+int main() {} // { dg-error "attach" }
diff --git a/gcc/testsuite/g++.dg/parse/linkage5.C
b/gcc/testsuite/g++.dg/parse/linkage5.C
new file mode 100644
index 00000000000..451406de69b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/parse/linkage5.C
@@ -0,0 +1,14 @@
+// { dg-do compile }
+// The main function shall not be declared with a linkage-specification.
+
+extern "C" {
+ int main(); // { dg-error "linkage" }
+}
+
+namespace foo {
+ extern "C" int main(); // { dg-error "linkage" }
+}
+
+extern "C++" int main(); // { dg-error "linkage" }
+
+extern "C" struct S { int main(); }; // OK
diff --git a/gcc/testsuite/g++.dg/parse/linkage6.C
b/gcc/testsuite/g++.dg/parse/linkage6.C
new file mode 100644
index 00000000000..44081c1544c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/parse/linkage6.C
@@ -0,0 +1,13 @@
+// { dg-do compile }
+// A program that declares an entity named main with C language linkage
+// (in any namespace) is ill-formed.
+
+namespace foo {
+ extern "C" int main; // { dg-error "linkage" }
+ extern "C" struct A {
+ int main; // OK
+ };
+ extern "C" struct B {
+ int main(); // OK
+ };
+}
