[clang] [C2y] Add test coverage and documentation for WG14 N3342 (PR #115494)

2024-11-08 Thread LLVM Continuous Integration via cfe-commits 

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-m68k-linux-cross` 
running on `suse-gary-m68k-cross` while building `clang` at step 4 "build stage 
1".

Full details are available at: 
https://lab.llvm.org/buildbot/#/builders/27/builds/1746


Here is the relevant piece of the build log for the reference

```
Step 4 (build stage 1) failure: 'ninja' (failure)
...
In file included from 
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Serialization/ASTReader.h:30,
 from 
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Serialization/ASTRecordReader.h:20,
 from 
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/lib/Serialization/ASTReaderDecl.cpp:55:
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:463:7:
 warning: ‘clang::Sema’ declared with greater visibility than the type of its 
field ‘clang::Sema::UnusedFileScopedDecls’ [-Wattributes]
  463 | class Sema final : public SemaBase {
  |   ^~~~
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:463:7:
 warning: ‘clang::Sema’ declared with greater visibility than the type of its 
field ‘clang::Sema::TentativeDefinitions’ [-Wattributes]
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:463:7:
 warning: ‘clang::Sema’ declared with greater visibility than the type of its 
field ‘clang::Sema::ExtVectorDecls’ [-Wattributes]
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:463:7:
 warning: ‘clang::Sema’ declared with greater visibility than the type of its 
field ‘clang::Sema::DelegatingCtorDecls’ [-Wattributes]
[133/328] Building CXX object 
tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/SemaExpr.cpp.o
FAILED: tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/SemaExpr.cpp.o 
/usr/bin/c++ -DCLANG_EXPORTS -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GLIBCXX_ASSERTIONS 
-D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS 
-D__STDC_LIMIT_MACROS 
-I/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/stage1/tools/clang/lib/Sema
 
-I/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/lib/Sema
 
-I/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include
 
-I/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/stage1/tools/clang/include
 
-I/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/stage1/include
 
-I/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/llvm/include
 -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden 
-Werror=date-time -fno-lifetime-dse -Wall -Wextra -Wno-unused-parameter 
-Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic 
-Wno-long-long -Wimplicit-fallthrough -Wno-maybe-uninitialized -Wno-nonnull 
-Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move 
-Wno-noexcept-type -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment 
-Wno-misleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color 
-ffunction-sections -fdata-sections -fno-common -Woverloaded-virtual 
-fno-strict-aliasing -O3 -DNDEBUG -std=c++17  -fno-exceptions -funwind-tables 
-fno-rtti -UNDEBUG -MD -MT 
tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/SemaExpr.cpp.o -MF 
tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/SemaExpr.cpp.o.d -o 
tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/SemaExpr.cpp.o -c 
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/lib/Sema/SemaExpr.cpp
In file included from 
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/lib/Sema/CheckExprLifetime.h:17,
 from 
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/lib/Sema/SemaExpr.cpp:13:
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:463:7:
 warning: ‘clang::Sema’ declared with greater visibility than the type of its 
field ‘clang::Sema::UnusedFileScopedDecls’ [-Wattributes]
  463 | class Sema final : public SemaBase {
  |   ^~~~
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:463:7:
 warning: ‘clang::Sema’ declared with greater visibility than the type of its 
field ‘clang::Sema::TentativeDefinitions’ [-Wattributes]
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:463:7:
 warning: ‘clang::Sema’ declared with greater visibility than the type of its 
field ‘clang::Sema::ExtVectorDecls’ [-Wattributes]
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/include/clang/Sema/Sema.h:463:7:
 warning: ‘clang:

[clang] [C2y] Add test coverage and documentation for WG14 N3342 (PR #115494)

2024-11-08 Thread LLVM Continuous Integration via cfe-commits 

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder 
`llvm-clang-x86_64-sie-ubuntu-fast` running on `sie-linux-worker` while 
building `clang` at step 6 "test-build-unified-tree-check-all".

Full details are available at: 
https://lab.llvm.org/buildbot/#/builders/144/builds/11191


Here is the relevant piece of the build log for the reference

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
 TEST 'Clang :: C/C2y/n3342.c' FAILED 
Exit Code: 1

Command Output (stderr):
--
RUN: at line 1: 
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/bin/clang 
-cc1 -internal-isystem 
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/lib/clang/20/include
 -nostdsysteminc -verify=expected,both -std=c2y -Wall -pedantic 
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/C/C2y/n3342.c
+ 
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/bin/clang 
-cc1 -internal-isystem 
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/lib/clang/20/include
 -nostdsysteminc -verify=expected,both -std=c2y -Wall -pedantic 
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/C/C2y/n3342.c
RUN: at line 2: 
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/bin/clang 
-cc1 -internal-isystem 
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/lib/clang/20/include
 -nostdsysteminc -verify=clang,both -Wall -pedantic 
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/C/C2y/n3342.c
+ 
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/bin/clang 
-cc1 -internal-isystem 
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/lib/clang/20/include
 -nostdsysteminc -verify=clang,both -Wall -pedantic 
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/C/C2y/n3342.c
error: 'both-warning' diagnostics seen but not expected: 
  File 
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/C/C2y/n3342.c
 Line 27: '_Atomic' is a C11 extension
1 error generated.

--




```



https://github.com/llvm/llvm-project/pull/115494
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[clang] [C2y] Add test coverage and documentation for WG14 N3342 (PR #115494)

2024-11-08 Thread Aaron Ballman via cfe-commits 

https://github.com/AaronBallman closed 
https://github.com/llvm/llvm-project/pull/115494
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[clang] [C2y] Add test coverage and documentation for WG14 N3342 (PR #115494)

2024-11-08 Thread Erich Keane via cfe-commits 

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


https://github.com/llvm/llvm-project/pull/115494
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[clang] [C2y] Add test coverage and documentation for WG14 N3342 (PR #115494)

2024-11-08 Thread via cfe-commits 

llvmbot wrote:




@llvm/pr-subscribers-clang

Author: Aaron Ballman (AaronBallman)


Changes

This paper made qualified function types implementation-defined. We have always 
supported this as an extension, so now we're documenting our behavior.

Note, we still warn about this by default even in C2y mode because a qualified 
function type is a sign of programmer confusion.

---
Full diff: https://github.com/llvm/llvm-project/pull/115494.diff


8 Files Affected:

- (modified) clang/docs/LanguageExtensions.rst (+17) 
- (modified) clang/docs/ReleaseNotes.rst (+5) 
- (modified) clang/include/clang/Basic/DiagnosticSemaKinds.td (+3-2) 
- (modified) clang/lib/Sema/SemaType.cpp (+6-3) 
- (added) clang/test/C/C2y/n3342.c (+29) 
- (modified) clang/test/Misc/warning-flags.c (+1-2) 
- (modified) clang/test/Sema/declspec.c (+2-2) 
- (modified) clang/www/c_status.html (+1-1) 


``diff
diff --git a/clang/docs/LanguageExtensions.rst 
b/clang/docs/LanguageExtensions.rst
index f7285352b9deb9..a051eb95898ecf 100644
--- a/clang/docs/LanguageExtensions.rst
+++ b/clang/docs/LanguageExtensions.rst
@@ -5974,3 +5974,20 @@ Clang guarantees the following behaviors:
   padding bits are initialized to zero.
 
 Currently, the above extension only applies to C source code, not C++.
+
+Qualified function types in C
+=
+Declaring a function with a qualified type in C is undefined behavior (C23 and
+earlier) or implementation-defined behavior (C2y). Clang allows a function type
+to be specified with the ``const`` and ``volatile`` qualifiers, but ignores the
+qualifications.
+
+.. code-block:: c
+
+   typedef int f(void);
+   const volatile f func; // Qualifier on function type has no effect.
+
+
+Note, Clang does not allow an ``_Atomic`` function type because
+of explicit constraints against atomically qualified (arrays and) function
+types.
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index d0c43ff11f7bae..d4bf05651a63eb 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -298,6 +298,11 @@ C2y Feature Support
   paper adopts Clang's existing practice, so there were no changes to compiler
   behavior.
 
+- Updated conformance for `N3342 
`_
+  which made qualified function types implementation-defined rather than
+  undefined. Clang has always accepted ``const`` and ``volatile`` qualified
+  function types by ignoring the qualifiers.
+
 C23 Feature Support
 ^^^
 
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td 
b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 6a244c276facd6..ae95ea6d558cb0 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -6241,8 +6241,9 @@ def err_typecheck_negative_array_size : Error<"array size 
is negative">;
 def warn_typecheck_function_qualifiers_ignored : Warning<
   "'%0' qualifier on function type %1 has no effect">,
   InGroup;
-def warn_typecheck_function_qualifiers_unspecified : Warning<
-  "'%0' qualifier on function type %1 has unspecified behavior">;
+def ext_typecheck_function_qualifiers_unspecified : ExtWarn<
+  "'%0' qualifier on function type %1 has no effect and is a Clang extension">,
+  InGroup;
 def warn_typecheck_reference_qualifiers : Warning<
   "'%0' qualifier on reference type %1 has no effect">,
   InGroup;
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index e526a11973975d..515b9f689a248a 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -1500,16 +1500,19 @@ static QualType 
ConvertDeclSpecToType(TypeProcessingState &state) {
 // C99 6.7.3p8:
 //   If the specification of a function type includes any type qualifiers,
 //   the behavior is undefined.
+// C2y changed this behavior to be implementation-defined. Clang defines
+// the behavior in all cases to ignore the qualifier, as in C++.
 // C++11 [dcl.fct]p7:
 //   The effect of a cv-qualifier-seq in a function declarator is not the
 //   same as adding cv-qualification on top of the function type. In the
 //   latter case, the cv-qualifiers are ignored.
 if (Result->isFunctionType()) {
+  unsigned DiagId = diag::warn_typecheck_function_qualifiers_ignored;
+  if (!S.getLangOpts().CPlusPlus && !S.getLangOpts().C2y)
+DiagId = diag::ext_typecheck_function_qualifiers_unspecified;
   diagnoseAndRemoveTypeQualifiers(
   S, DS, TypeQuals, Result, DeclSpec::TQ_const | DeclSpec::TQ_volatile,
-  S.getLangOpts().CPlusPlus
-  ? diag::warn_typecheck_function_qualifiers_ignored
-  : diag::warn_typecheck_function_qualifiers_unspecified);
+  DiagId);
   // No diagnostic for 'restrict' or '_Atomic' applied to a
   // function type; we'll diagnose those later, in BuildQualifiedType.
 }
diff --git a/clang/test/C/C2y/n3342.c b/clang/test/C/C

[clang] [C2y] Add test coverage and documentation for WG14 N3342 (PR #115494)

2024-11-08 Thread Aaron Ballman via cfe-commits 

https://github.com/AaronBallman created 
https://github.com/llvm/llvm-project/pull/115494

This paper made qualified function types implementation-defined. We have always 
supported this as an extension, so now we're documenting our behavior.

Note, we still warn about this by default even in C2y mode because a qualified 
function type is a sign of programmer confusion.

>From f82110a6443620049db0f0ac1f459e6bde86c260 Mon Sep 17 00:00:00 2001
From: Aaron Ballman 
Date: Fri, 8 Nov 2024 09:52:40 -0500
Subject: [PATCH] [C2y] Add test coverage and documentation for WG14 N3342

This paper made qualified function types implementation-defined. We
have always supported this as an extension, so now we're documenting
our behavior.

Note, we still warn about this by default even in C2y mode because a
qualified function type is a sign of programmer confusion.
---
 clang/docs/LanguageExtensions.rst | 17 +++
 clang/docs/ReleaseNotes.rst   |  5 
 .../clang/Basic/DiagnosticSemaKinds.td|  5 ++--
 clang/lib/Sema/SemaType.cpp   |  9 --
 clang/test/C/C2y/n3342.c  | 29 +++
 clang/test/Misc/warning-flags.c   |  3 +-
 clang/test/Sema/declspec.c|  4 +--
 clang/www/c_status.html   |  2 +-
 8 files changed, 64 insertions(+), 10 deletions(-)
 create mode 100644 clang/test/C/C2y/n3342.c

diff --git a/clang/docs/LanguageExtensions.rst 
b/clang/docs/LanguageExtensions.rst
index f7285352b9deb9..a051eb95898ecf 100644
--- a/clang/docs/LanguageExtensions.rst
+++ b/clang/docs/LanguageExtensions.rst
@@ -5974,3 +5974,20 @@ Clang guarantees the following behaviors:
   padding bits are initialized to zero.
 
 Currently, the above extension only applies to C source code, not C++.
+
+Qualified function types in C
+=
+Declaring a function with a qualified type in C is undefined behavior (C23 and
+earlier) or implementation-defined behavior (C2y). Clang allows a function type
+to be specified with the ``const`` and ``volatile`` qualifiers, but ignores the
+qualifications.
+
+.. code-block:: c
+
+   typedef int f(void);
+   const volatile f func; // Qualifier on function type has no effect.
+
+
+Note, Clang does not allow an ``_Atomic`` function type because
+of explicit constraints against atomically qualified (arrays and) function
+types.
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index d0c43ff11f7bae..d4bf05651a63eb 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -298,6 +298,11 @@ C2y Feature Support
   paper adopts Clang's existing practice, so there were no changes to compiler
   behavior.
 
+- Updated conformance for `N3342 
`_
+  which made qualified function types implementation-defined rather than
+  undefined. Clang has always accepted ``const`` and ``volatile`` qualified
+  function types by ignoring the qualifiers.
+
 C23 Feature Support
 ^^^
 
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td 
b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 6a244c276facd6..ae95ea6d558cb0 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -6241,8 +6241,9 @@ def err_typecheck_negative_array_size : Error<"array size 
is negative">;
 def warn_typecheck_function_qualifiers_ignored : Warning<
   "'%0' qualifier on function type %1 has no effect">,
   InGroup;
-def warn_typecheck_function_qualifiers_unspecified : Warning<
-  "'%0' qualifier on function type %1 has unspecified behavior">;
+def ext_typecheck_function_qualifiers_unspecified : ExtWarn<
+  "'%0' qualifier on function type %1 has no effect and is a Clang extension">,
+  InGroup;
 def warn_typecheck_reference_qualifiers : Warning<
   "'%0' qualifier on reference type %1 has no effect">,
   InGroup;
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index e526a11973975d..515b9f689a248a 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -1500,16 +1500,19 @@ static QualType 
ConvertDeclSpecToType(TypeProcessingState &state) {
 // C99 6.7.3p8:
 //   If the specification of a function type includes any type qualifiers,
 //   the behavior is undefined.
+// C2y changed this behavior to be implementation-defined. Clang defines
+// the behavior in all cases to ignore the qualifier, as in C++.
 // C++11 [dcl.fct]p7:
 //   The effect of a cv-qualifier-seq in a function declarator is not the
 //   same as adding cv-qualification on top of the function type. In the
 //   latter case, the cv-qualifiers are ignored.
 if (Result->isFunctionType()) {
+  unsigned DiagId = diag::warn_typecheck_function_qualifiers_ignored;
+  if (!S.getLangOpts().CPlusPlus && !S.getLangOpts().C2y)
+DiagId = diag::ext_typecheck_function