Split -Wcast-function-type into a separate group (llvm#86131)

We want to add -Wcast-function-type to -Wextra (as done in
1de7e6c), but we do not want to add
-Wcast-function-type-strict in at the same time
(https://lab.llvm.org/buildbot/#/builders/57/builds/33601/steps/5/logs/stdio).

This moves the existing warning to a new group
(-Wcast-function-type-mismatch), puts the new group under the existing
-Wcast-function-type warning group, and adds
-Wcast-function-type-mismatch to -Wextra.

clang/docs/ReleaseNotes.rst

@@ -198,7 +198,25 @@ Modified Compiler Flags
   ``-Wreturn-type``, and moved some of the diagnostics previously controlled by
   ``-Wreturn-type`` under this new flag. Fixes #GH72116.
 
-- Added ``-Wcast-function-type`` as a warning enabled by ``-Wextra``. #GH76872
+- Added ``-Wcast-function-type-mismatch`` under the ``-Wcast-function-type``
+  warning group. Moved the diagnostic previously controlled by
+  ``-Wcast-function-type`` to the new warning group and added
+  ``-Wcast-function-type-mismatch`` to ``-Wextra``. #GH76872
+
+  .. code-block:: c
+
+     int x(long);
+     typedef int (f2)(void*);
+     typedef int (f3)();
+
+     void func(void) {
+       // Diagnoses under -Wcast-function-type, -Wcast-function-type-mismatch,
+       // -Wcast-function-type-strict, -Wextra
+       f2 *b = (f2 *)x;
+       // Diagnoses under -Wcast-function-type, -Wcast-function-type-strict
+       f3 *c = (f3 *)x;
+     }
+
 
 Removed Compiler Flags
 -------------------------

clang/include/clang/Basic/DiagnosticGroups.td

@@ -573,7 +573,10 @@ def SelTypeCast : DiagGroup<"cast-of-sel-type">;
 def FunctionDefInObjCContainer : DiagGroup<"function-def-in-objc-container">;
 def BadFunctionCast : DiagGroup<"bad-function-cast">;
 def CastFunctionTypeStrict : DiagGroup<"cast-function-type-strict">;
-def CastFunctionType : DiagGroup<"cast-function-type", [CastFunctionTypeStrict]>;
+def CastFunctionTypeMismatch : DiagGroup<"cast-function-type-mismatch">;
+def CastFunctionType : DiagGroup<"cast-function-type",
+                                 [CastFunctionTypeStrict,
+                                  CastFunctionTypeMismatch]>;
 def ObjCPropertyImpl : DiagGroup<"objc-property-implementation">;
 def ObjCPropertyNoAttribute : DiagGroup<"objc-property-no-attribute">;
 def ObjCPropertyAssignOnObjectType : DiagGroup<"objc-property-assign-on-object-type">;
@@ -1038,7 +1041,7 @@ def Extra : DiagGroup<"extra", [
     EmptyInitStatement,
     StringConcatation,
     FUseLdPath,
-    CastFunctionType,
+    CastFunctionTypeMismatch,
   ]>;
 
 def Most : DiagGroup<"most", [

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -9058,7 +9058,7 @@ def warn_bad_function_cast : Warning<
   InGroup<BadFunctionCast>, DefaultIgnore;
 def warn_cast_function_type : Warning<
   "cast %diff{from $ to $ |}0,1converts to incompatible function type">,
-  InGroup<CastFunctionType>, DefaultIgnore;
+  InGroup<CastFunctionTypeMismatch>, DefaultIgnore;
 def warn_cast_function_type_strict : Warning<warn_cast_function_type.Summary>,
   InGroup<CastFunctionTypeStrict>, DefaultIgnore;
 def err_cast_pointer_to_non_pointer_int : Error<

clang/test/Sema/warn-cast-function-type-strict.c

@@ -1,5 +1,5 @@
-// RUN: %clang_cc1 %s -fsyntax-only -Wcast-function-type -verify
-// RUN: %clang_cc1 %s -fsyntax-only -Wcast-function-type-strict -verify
+// RUN: %clang_cc1 %s -fsyntax-only -Wcast-function-type -verify=expected,strict
+// RUN: %clang_cc1 %s -fsyntax-only -Wcast-function-type-strict -verify=expected,strict
 // RUN: %clang_cc1 %s -fsyntax-only -Wextra -Wno-ignored-qualifiers -verify
 
 int t(int array[static 12]);
@@ -32,13 +32,13 @@ f10 *j;
 void foo(void) {
   a = (f1 *)x;
   b = (f2 *)x; /* expected-warning {{cast from 'int (*)(long)' to 'f2 *' (aka 'int (*)(void *)') converts to incompatible function type}} */
-  c = (f3 *)x; /* expected-warning {{cast from 'int (*)(long)' to 'f3 *' (aka 'int (*)()') converts to incompatible function type}} */
+  c = (f3 *)x; /* strict-warning {{cast from 'int (*)(long)' to 'f3 *' (aka 'int (*)()') converts to incompatible function type}} */
   d = (f4 *)x; /* expected-warning {{cast from 'int (*)(long)' to 'f4 *' (aka 'void (*)()') converts to incompatible function type}} */
-  e = (f5 *)x; /* expected-warning {{cast from 'int (*)(long)' to 'f5 *' (aka 'void (*)(void)') converts to incompatible function type}} */
+  e = (f5 *)x; /* strict-warning {{cast from 'int (*)(long)' to 'f5 *' (aka 'void (*)(void)') converts to incompatible function type}} */
   f = (f6 *)x; /* expected-warning {{cast from 'int (*)(long)' to 'f6 *' (aka 'int (*)(long, int)') converts to incompatible function type}} */
-  g = (f7 *)x; /* expected-warning {{cast from 'int (*)(long)' to 'f7 *' (aka 'int (*)(long, ...)') converts to incompatible function type}} */
+  g = (f7 *)x; /* strict-warning {{cast from 'int (*)(long)' to 'f7 *' (aka 'int (*)(long, ...)') converts to incompatible function type}} */
   h = (f8 *)t;
   i = (f9 *)u;
   // FIXME: return type qualifier should not be included in the function type . Warning should be absent after this issue is fixed. https://github.com/llvm/llvm-project/issues/39494 .
-  j = (f10 *)v; /* expected-warning {{cast from 'const int (*)(int)' to 'f10 *' (aka 'int (*)(int)') converts to incompatible function type}} */
+  j = (f10 *)v; /* strict-warning {{cast from 'const int (*)(int)' to 'f10 *' (aka 'int (*)(int)') converts to incompatible function type}} */
 }

clang/test/SemaCXX/warn-cast-function-type-strict.cpp

@@ -1,5 +1,5 @@
-// RUN: %clang_cc1 %s -fblocks -fsyntax-only -Wcast-function-type -verify
-// RUN: %clang_cc1 %s -fblocks -fsyntax-only -Wcast-function-type-strict -verify
+// RUN: %clang_cc1 %s -fblocks -fsyntax-only -Wcast-function-type -verify=expected,strict
+// RUN: %clang_cc1 %s -fblocks -fsyntax-only -Wcast-function-type-strict -verify=expected,strict
 // RUN: %clang_cc1 %s -fblocks -fsyntax-only -Wextra -verify
 
 int x(long);
@@ -33,11 +33,11 @@ void foo() {
   a = (f1 *)x;
   b = (f2 *)x; // expected-warning {{cast from 'int (*)(long)' to 'f2 *' (aka 'int (*)(void *)') converts to incompatible function type}}
   b = reinterpret_cast<f2 *>(x); // expected-warning {{cast from 'int (*)(long)' to 'f2 *' (aka 'int (*)(void *)') converts to incompatible function type}}
-  c = (f3 *)x; // expected-warning {{cast from 'int (*)(long)' to 'f3 *' (aka 'int (*)(...)') converts to incompatible function type}}
+  c = (f3 *)x; // strict-warning {{cast from 'int (*)(long)' to 'f3 *' (aka 'int (*)(...)') converts to incompatible function type}}
   d = (f4 *)x; // expected-warning {{cast from 'int (*)(long)' to 'f4 *' (aka 'void (*)(...)') converts to incompatible function type}}
-  e = (f5 *)x; // expected-warning {{cast from 'int (*)(long)' to 'f5 *' (aka 'void (*)()') converts to incompatible function type}}
+  e = (f5 *)x; // strict-warning {{cast from 'int (*)(long)' to 'f5 *' (aka 'void (*)()') converts to incompatible function type}}
   f = (f6 *)x; // expected-warning {{cast from 'int (*)(long)' to 'f6 *' (aka 'int (*)(long, int)') converts to incompatible function type}}
-  g = (f7 *)x; // expected-warning {{cast from 'int (*)(long)' to 'f7 *' (aka 'int (*)(long, ...)') converts to incompatible function type}}
+  g = (f7 *)x; // strict-warning {{cast from 'int (*)(long)' to 'f7 *' (aka 'int (*)(long, ...)') converts to incompatible function type}}
 
   mf p1 = (mf)&S::foo; // expected-warning {{cast from 'void (S::*)(int *)' to 'mf' (aka 'void (S::*)(int)') converts to incompatible function type}}