[clang] [clang] Add test for CWG2811 "Clarify "use" of main" (PR #96168)

2024-06-21 Thread Vlad Serebrennikov via cfe-commits 

https://github.com/Endilll closed 
https://github.com/llvm/llvm-project/pull/96168
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[clang] [clang] Add test for CWG2811 "Clarify "use" of main" (PR #96168)

2024-06-20 Thread Vlad Serebrennikov via cfe-commits 

https://github.com/Endilll updated 
https://github.com/llvm/llvm-project/pull/96168

>From 7ac89c2758965fec2dd007954735e59d793d6a59 Mon Sep 17 00:00:00 2001
From: Vlad Serebrennikov 
Date: Thu, 20 Jun 2024 14:07:37 +0300
Subject: [PATCH 1/4] [clang] Add test for CWG2811 "Clarify "use" of main"

---
 .../clang/Basic/DiagnosticSemaKinds.td|  2 +-
 .../basic/basic.start/basic.start.init/p3.cpp |  4 ++--
 clang/test/CXX/drs/cwg28xx.cpp| 19 +++
 clang/www/cxx_dr_status.html  |  2 +-
 4 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td 
b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 14736784cff5f..b747d2637bd5f 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -964,7 +964,7 @@ def err_main_global_variable :
 def warn_main_redefined : Warning<"variable named 'main' with external linkage 
"
 "has undefined behavior">, InGroup;
 def ext_main_used : Extension<
-  "ISO C++ does not allow 'main' to be used by a program">, InGroup;
+  "expressions that refer to 'main' are an extension">, InGroup;
 
 /// parser diagnostics
 def ext_no_declarators : ExtWarn<"declaration does not declare anything">,
diff --git a/clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp 
b/clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp
index 506232ebacc4c..8f215172235c2 100644
--- a/clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp
+++ b/clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp
@@ -16,9 +16,9 @@ int main(int argc, char **argv)
   = delete; // expected-error {{'main' is not allowed to be deleted}}
 #else
 {
-  int (*pmain)(int, char**) =  // expected-error {{ISO C++ does not 
allow 'main' to be used by a program}}
+  int (*pmain)(int, char**) =  // expected-error {{expressions that 
refer to 'main' are an extension}}
 
   if (argc)
-main(0, 0); // expected-error {{ISO C++ does not allow 'main' to be used 
by a program}}
+main(0, 0); // expected-error {{expressions that refer to 'main' are an 
extension}}
 }
 #endif
diff --git a/clang/test/CXX/drs/cwg28xx.cpp b/clang/test/CXX/drs/cwg28xx.cpp
index da81eccc8dc22..049d90a1f7b20 100644
--- a/clang/test/CXX/drs/cwg28xx.cpp
+++ b/clang/test/CXX/drs/cwg28xx.cpp
@@ -6,6 +6,25 @@
 // RUN: %clang_cc1 -std=c++23 -pedantic-errors 
-verify=expected,since-cxx20,since-cxx23 %s
 // RUN: %clang_cc1 -std=c++2c -pedantic-errors 
-verify=expected,since-cxx20,since-cxx23,since-cxx26 %s
 
+
+int main() {} // required for cwg2811
+
+namespace cwg2811 { // cwg2811: 3.5
+#if __cplusplus >= 201103L
+void f() {
+  (void)[&] {
+using T = decltype(main);
+// expected-error@-1 {{expressions that refer to 'main' are an extension}}
+  };
+  using T2 = decltype(main);
+  // expected-error@-1 {{expressions that refer to 'main' are an extension}}
+}
+
+using T = decltype(main);
+// expected-error@-1 {{expressions that refer to 'main' are an extension}}
+#endif
+} // namespace cwg2811
+
 namespace cwg2819 { // cwg2819: 19 tentatively ready 2023-12-01
 #if __cpp_constexpr >= 202306L
   constexpr void* p = nullptr;
diff --git a/clang/www/cxx_dr_status.html b/clang/www/cxx_dr_status.html
index dac38cedfcb75..d6b7c32dd844d 100755
--- a/clang/www/cxx_dr_status.html
+++ b/clang/www/cxx_dr_status.html
@@ -16675,7 +16675,7 @@ C++ defect report implementation 
status
 https://cplusplus.github.io/CWG/issues/2811.html;>2811
 DR
 Clarify "use" of main
-Unknown
+Clang 3.5
   
   
 https://cplusplus.github.io/CWG/issues/2812.html;>2812

>From 7043728a9b59ce6fb741f83adec0ae866b8d78fa Mon Sep 17 00:00:00 2001
From: Vlad Serebrennikov 
Date: Thu, 20 Jun 2024 15:56:21 +0300
Subject: [PATCH 2/4] Add tests for a `main` function inside a namespace

---
 clang/test/CXX/drs/cwg28xx.cpp | 5 +
 1 file changed, 5 insertions(+)

diff --git a/clang/test/CXX/drs/cwg28xx.cpp b/clang/test/CXX/drs/cwg28xx.cpp
index 049d90a1f7b20..66ffbdf5e0d2b 100644
--- a/clang/test/CXX/drs/cwg28xx.cpp
+++ b/clang/test/CXX/drs/cwg28xx.cpp
@@ -22,6 +22,11 @@ void f() {
 
 using T = decltype(main);
 // expected-error@-1 {{expressions that refer to 'main' are an extension}}
+
+int main();
+
+using U = decltype(main);
+using U2 = decltype();
 #endif
 } // namespace cwg2811
 

>From f3bcd9da2fa99fb6bab913adb9139e76145b46a2 Mon Sep 17 00:00:00 2001
From: Vlad Serebrennikov 
Date: Thu, 20 Jun 2024 16:46:02 +0300
Subject: [PATCH 3/4] Clarify that it's a Clang extension as @AaronBallman
 suggested

---
 clang/include/clang/Basic/DiagnosticSemaKinds.td | 2 +-
 clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp | 4 ++--
 clang/test/CXX/drs/cwg28xx.cpp   | 6 +++---
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td 
b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index b747d2637bd5f..8cdc05f360003 100644
---

[clang] [clang] Add test for CWG2811 "Clarify "use" of main" (PR #96168)

2024-06-20 Thread Aaron Ballman via cfe-commits 


@@ -964,7 +964,7 @@ def err_main_global_variable :
 def warn_main_redefined : Warning<"variable named 'main' with external linkage 
"
 "has undefined behavior">, InGroup;
 def ext_main_used : Extension<
-  "ISO C++ does not allow 'main' to be used by a program">, InGroup;
+  "expressions that refer to 'main' are an extension">, InGroup;

AaronBallman wrote:

Good point about `decltype` accepting an expression. This is fine by me.

https://github.com/llvm/llvm-project/pull/96168
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[clang] [clang] Add test for CWG2811 "Clarify "use" of main" (PR #96168)

2024-06-20 Thread Aaron Ballman via cfe-commits 

https://github.com/AaronBallman approved this pull request.

LGTM!

https://github.com/llvm/llvm-project/pull/96168
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[clang] [clang] Add test for CWG2811 "Clarify "use" of main" (PR #96168)

2024-06-20 Thread via cfe-commits 

https://github.com/cor3ntin approved this pull request.

LGTM if @AaronBallman is happy

("expressions that... are an extensions" still sounds weird to me, cf previous 
comment)

https://github.com/llvm/llvm-project/pull/96168
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[clang] [clang] Add test for CWG2811 "Clarify "use" of main" (PR #96168)

2024-06-20 Thread Vlad Serebrennikov via cfe-commits 

Endilll wrote:

> do we have test that this is fine?
> 
> ```
> namespace foo {
> int main();
> using a = decltype();
> }```
> ```

Thank you, I added the tests.

https://github.com/llvm/llvm-project/pull/96168
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[clang] [clang] Add test for CWG2811 "Clarify "use" of main" (PR #96168)

2024-06-20 Thread Vlad Serebrennikov via cfe-commits 


@@ -964,7 +964,7 @@ def err_main_global_variable :
 def warn_main_redefined : Warning<"variable named 'main' with external linkage 
"
 "has undefined behavior">, InGroup;
 def ext_main_used : Extension<
-  "ISO C++ does not allow 'main' to be used by a program">, InGroup;
+  "expressions that refer to 'main' are an extension">, InGroup;

Endilll wrote:

I applied the suggestion.

https://github.com/llvm/llvm-project/pull/96168
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[clang] [clang] Add test for CWG2811 "Clarify "use" of main" (PR #96168)

2024-06-20 Thread Vlad Serebrennikov via cfe-commits 

https://github.com/Endilll updated 
https://github.com/llvm/llvm-project/pull/96168

>From 7ac89c2758965fec2dd007954735e59d793d6a59 Mon Sep 17 00:00:00 2001
From: Vlad Serebrennikov 
Date: Thu, 20 Jun 2024 14:07:37 +0300
Subject: [PATCH 1/3] [clang] Add test for CWG2811 "Clarify "use" of main"

---
 .../clang/Basic/DiagnosticSemaKinds.td|  2 +-
 .../basic/basic.start/basic.start.init/p3.cpp |  4 ++--
 clang/test/CXX/drs/cwg28xx.cpp| 19 +++
 clang/www/cxx_dr_status.html  |  2 +-
 4 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td 
b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 14736784cff5f..b747d2637bd5f 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -964,7 +964,7 @@ def err_main_global_variable :
 def warn_main_redefined : Warning<"variable named 'main' with external linkage 
"
 "has undefined behavior">, InGroup;
 def ext_main_used : Extension<
-  "ISO C++ does not allow 'main' to be used by a program">, InGroup;
+  "expressions that refer to 'main' are an extension">, InGroup;
 
 /// parser diagnostics
 def ext_no_declarators : ExtWarn<"declaration does not declare anything">,
diff --git a/clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp 
b/clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp
index 506232ebacc4c..8f215172235c2 100644
--- a/clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp
+++ b/clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp
@@ -16,9 +16,9 @@ int main(int argc, char **argv)
   = delete; // expected-error {{'main' is not allowed to be deleted}}
 #else
 {
-  int (*pmain)(int, char**) =  // expected-error {{ISO C++ does not 
allow 'main' to be used by a program}}
+  int (*pmain)(int, char**) =  // expected-error {{expressions that 
refer to 'main' are an extension}}
 
   if (argc)
-main(0, 0); // expected-error {{ISO C++ does not allow 'main' to be used 
by a program}}
+main(0, 0); // expected-error {{expressions that refer to 'main' are an 
extension}}
 }
 #endif
diff --git a/clang/test/CXX/drs/cwg28xx.cpp b/clang/test/CXX/drs/cwg28xx.cpp
index da81eccc8dc22..049d90a1f7b20 100644
--- a/clang/test/CXX/drs/cwg28xx.cpp
+++ b/clang/test/CXX/drs/cwg28xx.cpp
@@ -6,6 +6,25 @@
 // RUN: %clang_cc1 -std=c++23 -pedantic-errors 
-verify=expected,since-cxx20,since-cxx23 %s
 // RUN: %clang_cc1 -std=c++2c -pedantic-errors 
-verify=expected,since-cxx20,since-cxx23,since-cxx26 %s
 
+
+int main() {} // required for cwg2811
+
+namespace cwg2811 { // cwg2811: 3.5
+#if __cplusplus >= 201103L
+void f() {
+  (void)[&] {
+using T = decltype(main);
+// expected-error@-1 {{expressions that refer to 'main' are an extension}}
+  };
+  using T2 = decltype(main);
+  // expected-error@-1 {{expressions that refer to 'main' are an extension}}
+}
+
+using T = decltype(main);
+// expected-error@-1 {{expressions that refer to 'main' are an extension}}
+#endif
+} // namespace cwg2811
+
 namespace cwg2819 { // cwg2819: 19 tentatively ready 2023-12-01
 #if __cpp_constexpr >= 202306L
   constexpr void* p = nullptr;
diff --git a/clang/www/cxx_dr_status.html b/clang/www/cxx_dr_status.html
index dac38cedfcb75..d6b7c32dd844d 100755
--- a/clang/www/cxx_dr_status.html
+++ b/clang/www/cxx_dr_status.html
@@ -16675,7 +16675,7 @@ C++ defect report implementation 
status
 https://cplusplus.github.io/CWG/issues/2811.html;>2811
 DR
 Clarify "use" of main
-Unknown
+Clang 3.5
   
   
 https://cplusplus.github.io/CWG/issues/2812.html;>2812

>From 7043728a9b59ce6fb741f83adec0ae866b8d78fa Mon Sep 17 00:00:00 2001
From: Vlad Serebrennikov 
Date: Thu, 20 Jun 2024 15:56:21 +0300
Subject: [PATCH 2/3] Add tests for a `main` function inside a namespace

---
 clang/test/CXX/drs/cwg28xx.cpp | 5 +
 1 file changed, 5 insertions(+)

diff --git a/clang/test/CXX/drs/cwg28xx.cpp b/clang/test/CXX/drs/cwg28xx.cpp
index 049d90a1f7b20..66ffbdf5e0d2b 100644
--- a/clang/test/CXX/drs/cwg28xx.cpp
+++ b/clang/test/CXX/drs/cwg28xx.cpp
@@ -22,6 +22,11 @@ void f() {
 
 using T = decltype(main);
 // expected-error@-1 {{expressions that refer to 'main' are an extension}}
+
+int main();
+
+using U = decltype(main);
+using U2 = decltype();
 #endif
 } // namespace cwg2811
 

>From f3bcd9da2fa99fb6bab913adb9139e76145b46a2 Mon Sep 17 00:00:00 2001
From: Vlad Serebrennikov 
Date: Thu, 20 Jun 2024 16:46:02 +0300
Subject: [PATCH 3/3] Clarify that it's a Clang extension as @AaronBallman
 suggested

---
 clang/include/clang/Basic/DiagnosticSemaKinds.td | 2 +-
 clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp | 4 ++--
 clang/test/CXX/drs/cwg28xx.cpp   | 6 +++---
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td 
b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index b747d2637bd5f..8cdc05f360003 100644
---

[clang] [clang] Add test for CWG2811 "Clarify "use" of main" (PR #96168)

2024-06-20 Thread Vlad Serebrennikov via cfe-commits 

https://github.com/Endilll updated 
https://github.com/llvm/llvm-project/pull/96168

>From 7ac89c2758965fec2dd007954735e59d793d6a59 Mon Sep 17 00:00:00 2001
From: Vlad Serebrennikov 
Date: Thu, 20 Jun 2024 14:07:37 +0300
Subject: [PATCH 1/2] [clang] Add test for CWG2811 "Clarify "use" of main"

---
 .../clang/Basic/DiagnosticSemaKinds.td|  2 +-
 .../basic/basic.start/basic.start.init/p3.cpp |  4 ++--
 clang/test/CXX/drs/cwg28xx.cpp| 19 +++
 clang/www/cxx_dr_status.html  |  2 +-
 4 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td 
b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 14736784cff5f..b747d2637bd5f 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -964,7 +964,7 @@ def err_main_global_variable :
 def warn_main_redefined : Warning<"variable named 'main' with external linkage 
"
 "has undefined behavior">, InGroup;
 def ext_main_used : Extension<
-  "ISO C++ does not allow 'main' to be used by a program">, InGroup;
+  "expressions that refer to 'main' are an extension">, InGroup;
 
 /// parser diagnostics
 def ext_no_declarators : ExtWarn<"declaration does not declare anything">,
diff --git a/clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp 
b/clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp
index 506232ebacc4c..8f215172235c2 100644
--- a/clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp
+++ b/clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp
@@ -16,9 +16,9 @@ int main(int argc, char **argv)
   = delete; // expected-error {{'main' is not allowed to be deleted}}
 #else
 {
-  int (*pmain)(int, char**) =  // expected-error {{ISO C++ does not 
allow 'main' to be used by a program}}
+  int (*pmain)(int, char**) =  // expected-error {{expressions that 
refer to 'main' are an extension}}
 
   if (argc)
-main(0, 0); // expected-error {{ISO C++ does not allow 'main' to be used 
by a program}}
+main(0, 0); // expected-error {{expressions that refer to 'main' are an 
extension}}
 }
 #endif
diff --git a/clang/test/CXX/drs/cwg28xx.cpp b/clang/test/CXX/drs/cwg28xx.cpp
index da81eccc8dc22..049d90a1f7b20 100644
--- a/clang/test/CXX/drs/cwg28xx.cpp
+++ b/clang/test/CXX/drs/cwg28xx.cpp
@@ -6,6 +6,25 @@
 // RUN: %clang_cc1 -std=c++23 -pedantic-errors 
-verify=expected,since-cxx20,since-cxx23 %s
 // RUN: %clang_cc1 -std=c++2c -pedantic-errors 
-verify=expected,since-cxx20,since-cxx23,since-cxx26 %s
 
+
+int main() {} // required for cwg2811
+
+namespace cwg2811 { // cwg2811: 3.5
+#if __cplusplus >= 201103L
+void f() {
+  (void)[&] {
+using T = decltype(main);
+// expected-error@-1 {{expressions that refer to 'main' are an extension}}
+  };
+  using T2 = decltype(main);
+  // expected-error@-1 {{expressions that refer to 'main' are an extension}}
+}
+
+using T = decltype(main);
+// expected-error@-1 {{expressions that refer to 'main' are an extension}}
+#endif
+} // namespace cwg2811
+
 namespace cwg2819 { // cwg2819: 19 tentatively ready 2023-12-01
 #if __cpp_constexpr >= 202306L
   constexpr void* p = nullptr;
diff --git a/clang/www/cxx_dr_status.html b/clang/www/cxx_dr_status.html
index dac38cedfcb75..d6b7c32dd844d 100755
--- a/clang/www/cxx_dr_status.html
+++ b/clang/www/cxx_dr_status.html
@@ -16675,7 +16675,7 @@ C++ defect report implementation 
status
 https://cplusplus.github.io/CWG/issues/2811.html;>2811
 DR
 Clarify "use" of main
-Unknown
+Clang 3.5
   
   
 https://cplusplus.github.io/CWG/issues/2812.html;>2812

>From 7043728a9b59ce6fb741f83adec0ae866b8d78fa Mon Sep 17 00:00:00 2001
From: Vlad Serebrennikov 
Date: Thu, 20 Jun 2024 15:56:21 +0300
Subject: [PATCH 2/2] Add tests for a `main` function inside a namespace

---
 clang/test/CXX/drs/cwg28xx.cpp | 5 +
 1 file changed, 5 insertions(+)

diff --git a/clang/test/CXX/drs/cwg28xx.cpp b/clang/test/CXX/drs/cwg28xx.cpp
index 049d90a1f7b20..66ffbdf5e0d2b 100644
--- a/clang/test/CXX/drs/cwg28xx.cpp
+++ b/clang/test/CXX/drs/cwg28xx.cpp
@@ -22,6 +22,11 @@ void f() {
 
 using T = decltype(main);
 // expected-error@-1 {{expressions that refer to 'main' are an extension}}
+
+int main();
+
+using U = decltype(main);
+using U2 = decltype();
 #endif
 } // namespace cwg2811
 

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[clang] [clang] Add test for CWG2811 "Clarify "use" of main" (PR #96168)

2024-06-20 Thread via cfe-commits 


@@ -964,7 +964,7 @@ def err_main_global_variable :
 def warn_main_redefined : Warning<"variable named 'main' with external linkage 
"
 "has undefined behavior">, InGroup;
 def ext_main_used : Extension<
-  "ISO C++ does not allow 'main' to be used by a program">, InGroup;
+  "expressions that refer to 'main' are an extension">, InGroup;

cor3ntin wrote:

no, it's not. `main` is named by an expression (which is unevaluated)

https://github.com/llvm/llvm-project/pull/96168
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[clang] [clang] Add test for CWG2811 "Clarify "use" of main" (PR #96168)

2024-06-20 Thread Aaron Ballman via cfe-commits 


@@ -964,7 +964,7 @@ def err_main_global_variable :
 def warn_main_redefined : Warning<"variable named 'main' with external linkage 
"
 "has undefined behavior">, InGroup;
 def ext_main_used : Extension<
-  "ISO C++ does not allow 'main' to be used by a program">, InGroup;
+  "expressions that refer to 'main' are an extension">, InGroup;

AaronBallman wrote:

```suggestion
  "expressions that refer to 'main' are a Clang extension">, InGroup;
```
I think there's work to be done for full conformance here though. For example, 
this DR clarified that the following code is valid, but we still diagnose it as 
an extension:
```
int main() {}
decltype(main) maine;
```
https://godbolt.org/z/nn8rd483Y

https://github.com/llvm/llvm-project/pull/96168
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[clang] [clang] Add test for CWG2811 "Clarify "use" of main" (PR #96168)

2024-06-20 Thread Vlad Serebrennikov via cfe-commits 

Endilll wrote:

> it's clearer that it's not conforming (at the very least we should say 
> something like "clang extension"

As someone who was a user of Clang not so long ago, I have to say that the only 
thing "ISO C++ requires" conveyed to me was "you're doing something wrong". For 
me it never had a clear interpretation "you're asking for an extension, but 
we're not giving it to you". On the other hand, I believe the word "extension" 
is clearly understood to describe something outside of ISO C++, somewhat by 
definition. At least that would match my understanding 3-4 years ago.

CC @AaronBallman I remember we discussed it offline a while ago.

https://github.com/llvm/llvm-project/pull/96168
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[clang] [clang] Add test for CWG2811 "Clarify "use" of main" (PR #96168)

2024-06-20 Thread via cfe-commits 

cor3ntin wrote:

I think I prefer the current wording, it's clearer that it's not conforming (at 
the very least we should say something like "clang extension". and maybe 
"referring to main is a clang extension".
LGTM otherwise

do we have test that this is fine?

```
namespace foo {
int main();
using a = decltype();
}```

https://github.com/llvm/llvm-project/pull/96168
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[clang] [clang] Add test for CWG2811 "Clarify "use" of main" (PR #96168)

2024-06-20 Thread via cfe-commits 

llvmbot wrote:




@llvm/pr-subscribers-clang

Author: Vlad Serebrennikov (Endilll)


Changes

This patch covers [CWG2811](https://cplusplus.github.io/CWG/issues/2811.html) 
"Clarify "use" of main", basically adding a test for `-Wmain`, focusing on 
usages of `main` in unevaluated contexts.

To my understanding, the diagnostic message is based on the wording, so I 
updated it based on the new wording. I also replaces "ISO C++ requires" with a 
phrasing that explicitly says "extension".


---
Full diff: https://github.com/llvm/llvm-project/pull/96168.diff


4 Files Affected:

- (modified) clang/include/clang/Basic/DiagnosticSemaKinds.td (+1-1) 
- (modified) clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp (+2-2) 
- (modified) clang/test/CXX/drs/cwg28xx.cpp (+19) 
- (modified) clang/www/cxx_dr_status.html (+1-1) 


``diff
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td 
b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 14736784cff5f..b747d2637bd5f 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -964,7 +964,7 @@ def err_main_global_variable :
 def warn_main_redefined : Warning<"variable named 'main' with external linkage 
"
 "has undefined behavior">, InGroup;
 def ext_main_used : Extension<
-  "ISO C++ does not allow 'main' to be used by a program">, InGroup;
+  "expressions that refer to 'main' are an extension">, InGroup;
 
 /// parser diagnostics
 def ext_no_declarators : ExtWarn<"declaration does not declare anything">,
diff --git a/clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp 
b/clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp
index 506232ebacc4c..8f215172235c2 100644
--- a/clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp
+++ b/clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp
@@ -16,9 +16,9 @@ int main(int argc, char **argv)
   = delete; // expected-error {{'main' is not allowed to be deleted}}
 #else
 {
-  int (*pmain)(int, char**) =  // expected-error {{ISO C++ does not 
allow 'main' to be used by a program}}
+  int (*pmain)(int, char**) =  // expected-error {{expressions that 
refer to 'main' are an extension}}
 
   if (argc)
-main(0, 0); // expected-error {{ISO C++ does not allow 'main' to be used 
by a program}}
+main(0, 0); // expected-error {{expressions that refer to 'main' are an 
extension}}
 }
 #endif
diff --git a/clang/test/CXX/drs/cwg28xx.cpp b/clang/test/CXX/drs/cwg28xx.cpp
index da81eccc8dc22..049d90a1f7b20 100644
--- a/clang/test/CXX/drs/cwg28xx.cpp
+++ b/clang/test/CXX/drs/cwg28xx.cpp
@@ -6,6 +6,25 @@
 // RUN: %clang_cc1 -std=c++23 -pedantic-errors 
-verify=expected,since-cxx20,since-cxx23 %s
 // RUN: %clang_cc1 -std=c++2c -pedantic-errors 
-verify=expected,since-cxx20,since-cxx23,since-cxx26 %s
 
+
+int main() {} // required for cwg2811
+
+namespace cwg2811 { // cwg2811: 3.5
+#if __cplusplus >= 201103L
+void f() {
+  (void)[&] {
+using T = decltype(main);
+// expected-error@-1 {{expressions that refer to 'main' are an extension}}
+  };
+  using T2 = decltype(main);
+  // expected-error@-1 {{expressions that refer to 'main' are an extension}}
+}
+
+using T = decltype(main);
+// expected-error@-1 {{expressions that refer to 'main' are an extension}}
+#endif
+} // namespace cwg2811
+
 namespace cwg2819 { // cwg2819: 19 tentatively ready 2023-12-01
 #if __cpp_constexpr >= 202306L
   constexpr void* p = nullptr;
diff --git a/clang/www/cxx_dr_status.html b/clang/www/cxx_dr_status.html
index dac38cedfcb75..d6b7c32dd844d 100755
--- a/clang/www/cxx_dr_status.html
+++ b/clang/www/cxx_dr_status.html
@@ -16675,7 +16675,7 @@ C++ defect report implementation 
status
 https://cplusplus.github.io/CWG/issues/2811.html;>2811
 DR
 Clarify "use" of main
-Unknown
+Clang 3.5
   
   
 https://cplusplus.github.io/CWG/issues/2812.html;>2812

``




https://github.com/llvm/llvm-project/pull/96168
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[clang] [clang] Add test for CWG2811 "Clarify "use" of main" (PR #96168)

2024-06-20 Thread Vlad Serebrennikov via cfe-commits 

https://github.com/Endilll created 
https://github.com/llvm/llvm-project/pull/96168

This patch covers [CWG2811](https://cplusplus.github.io/CWG/issues/2811.html) 
"Clarify "use" of main", basically adding a test for `-Wmain`, focusing on 
usages of `main` in unevaluated contexts.

To my understanding, the diagnostic message is based on the wording, so I 
updated it based on the new wording. I also replaces "ISO C++ requires" with a 
phrasing that explicitly says "extension".


>From 7ac89c2758965fec2dd007954735e59d793d6a59 Mon Sep 17 00:00:00 2001
From: Vlad Serebrennikov 
Date: Thu, 20 Jun 2024 14:07:37 +0300
Subject: [PATCH] [clang] Add test for CWG2811 "Clarify "use" of main"

---
 .../clang/Basic/DiagnosticSemaKinds.td|  2 +-
 .../basic/basic.start/basic.start.init/p3.cpp |  4 ++--
 clang/test/CXX/drs/cwg28xx.cpp| 19 +++
 clang/www/cxx_dr_status.html  |  2 +-
 4 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td 
b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 14736784cff5f..b747d2637bd5f 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -964,7 +964,7 @@ def err_main_global_variable :
 def warn_main_redefined : Warning<"variable named 'main' with external linkage 
"
 "has undefined behavior">, InGroup;
 def ext_main_used : Extension<
-  "ISO C++ does not allow 'main' to be used by a program">, InGroup;
+  "expressions that refer to 'main' are an extension">, InGroup;
 
 /// parser diagnostics
 def ext_no_declarators : ExtWarn<"declaration does not declare anything">,
diff --git a/clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp 
b/clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp
index 506232ebacc4c..8f215172235c2 100644
--- a/clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp
+++ b/clang/test/CXX/basic/basic.start/basic.start.init/p3.cpp
@@ -16,9 +16,9 @@ int main(int argc, char **argv)
   = delete; // expected-error {{'main' is not allowed to be deleted}}
 #else
 {
-  int (*pmain)(int, char**) =  // expected-error {{ISO C++ does not 
allow 'main' to be used by a program}}
+  int (*pmain)(int, char**) =  // expected-error {{expressions that 
refer to 'main' are an extension}}
 
   if (argc)
-main(0, 0); // expected-error {{ISO C++ does not allow 'main' to be used 
by a program}}
+main(0, 0); // expected-error {{expressions that refer to 'main' are an 
extension}}
 }
 #endif
diff --git a/clang/test/CXX/drs/cwg28xx.cpp b/clang/test/CXX/drs/cwg28xx.cpp
index da81eccc8dc22..049d90a1f7b20 100644
--- a/clang/test/CXX/drs/cwg28xx.cpp
+++ b/clang/test/CXX/drs/cwg28xx.cpp
@@ -6,6 +6,25 @@
 // RUN: %clang_cc1 -std=c++23 -pedantic-errors 
-verify=expected,since-cxx20,since-cxx23 %s
 // RUN: %clang_cc1 -std=c++2c -pedantic-errors 
-verify=expected,since-cxx20,since-cxx23,since-cxx26 %s
 
+
+int main() {} // required for cwg2811
+
+namespace cwg2811 { // cwg2811: 3.5
+#if __cplusplus >= 201103L
+void f() {
+  (void)[&] {
+using T = decltype(main);
+// expected-error@-1 {{expressions that refer to 'main' are an extension}}
+  };
+  using T2 = decltype(main);
+  // expected-error@-1 {{expressions that refer to 'main' are an extension}}
+}
+
+using T = decltype(main);
+// expected-error@-1 {{expressions that refer to 'main' are an extension}}
+#endif
+} // namespace cwg2811
+
 namespace cwg2819 { // cwg2819: 19 tentatively ready 2023-12-01
 #if __cpp_constexpr >= 202306L
   constexpr void* p = nullptr;
diff --git a/clang/www/cxx_dr_status.html b/clang/www/cxx_dr_status.html
index dac38cedfcb75..d6b7c32dd844d 100755
--- a/clang/www/cxx_dr_status.html
+++ b/clang/www/cxx_dr_status.html
@@ -16675,7 +16675,7 @@ C++ defect report implementation 
status
 https://cplusplus.github.io/CWG/issues/2811.html;>2811
 DR
 Clarify "use" of main
-Unknown
+Clang 3.5
   
   
 https://cplusplus.github.io/CWG/issues/2812.html;>2812

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