[Clang] [Sema] Make -Wincompatible-pointer-types an error by default (#157364)

GCC 14 also made this an error by default, so we’re following suit.

Fixes #74605

Author: Sirraide

clang-tools-extra/test/clang-tidy/checkers/bugprone/easily-swappable-parameters-implicits.c

@@ -1,4 +1,4 @@
-// RUN: %check_clang_tidy %s bugprone-easily-swappable-parameters %t \
+// RUN: %check_clang_tidy %s --extra-arg=-Wno-error=incompatible-pointer-types bugprone-easily-swappable-parameters %t \
 // RUN:   -config='{CheckOptions: { \
 // RUN:     bugprone-easily-swappable-parameters.MinimumLength: 2, \
 // RUN:     bugprone-easily-swappable-parameters.IgnoredParameterNames: "", \

clang/docs/ReleaseNotes.rst

@@ -58,6 +58,9 @@ C/C++ Language Potentially Breaking Changes
 
 - The ``__has_builtin`` function now only considers the currently active target when being used with target offloading.
 
+- The ``-Wincompatible-pointer-types`` diagnostic now defaults to an error;
+  it can still be downgraded to a warning by passing ``-Wno-error=incompatible-pointer-types``. (#GH74605)
+
 C++ Specific Potentially Breaking Changes
 -----------------------------------------
 - For C++20 modules, the Reduced BMI mode will be the default option. This may introduce

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -9048,7 +9048,7 @@ def ext_typecheck_convert_incompatible_pointer : ExtWarn<
   "; take the address with &|"
   "; remove *|"
   "; remove &}3">,
-  InGroup<IncompatiblePointerTypes>;
+  InGroup<IncompatiblePointerTypes>, DefaultError;
 def err_typecheck_convert_incompatible_pointer : Error<
   "incompatible pointer types "
   "%select{%diff{assigning to $ from $|assigning to different types}0,1"

clang/test/APINotes/nullability.c

@@ -15,7 +15,7 @@ int main() {
 
   take_pointer_and_int(0, 0); // expected-warning{{null passed to a callee that requires a non-null argument}}
 
-  float *fp = global_int; // expected-warning{{incompatible pointer types initializing 'float *' with an expression of type 'int * _Nonnull'}}
+  float *fp = global_int; // expected-error{{incompatible pointer types initializing 'float *' with an expression of type 'int * _Nonnull'}}
   return 0;
 }
 

clang/test/APINotes/nullability.m

@@ -11,10 +11,10 @@ int main() {
   A *a;
 
 #if SWIFT_VERSION_3_0
-  float *fp =  // expected-warning{{incompatible pointer types initializing 'float *' with an expression of type 'A * _Nullable'}}
+  float *fp =  // expected-error{{incompatible pointer types initializing 'float *' with an expression of type 'A * _Nullable'}}
     [a transform: 0 integer: 0];
 #else
-  float *fp =  // expected-warning{{incompatible pointer types initializing 'float *' with an expression of type 'A *'}}
+  float *fp =  // expected-error{{incompatible pointer types initializing 'float *' with an expression of type 'A *'}}
     [a transform: 0 integer: 0]; // expected-warning{{null passed to a callee that requires a non-null argument}}
 #endif
 

clang/test/APINotes/types.m

@@ -12,17 +12,17 @@
 // CHECK-NEXT: } AnonEnumWithTypedefName
 
 void test(OverriddenTypes *overridden) {
-  int *ip1 = global_int_ptr; // expected-warning{{incompatible pointer types initializing 'int *' with an expression of type 'double (*)(int, int)'}}
+  int *ip1 = global_int_ptr; // expected-error{{incompatible pointer types initializing 'int *' with an expression of type 'double (*)(int, int)'}}
 
-  int *ip2 = global_int_fun( // expected-warning{{incompatible pointer types initializing 'int *' with an expression of type 'char *'}}
-               ip2, // expected-warning{{incompatible pointer types passing 'int *' to parameter of type 'double *'}}
-               ip2); // expected-warning{{incompatible pointer types passing 'int *' to parameter of type 'float *'}}
+  int *ip2 = global_int_fun( // expected-error{{incompatible pointer types initializing 'int *' with an expression of type 'char *'}}
+               ip2, // expected-error{{incompatible pointer types passing 'int *' to parameter of type 'double *'}}
+               ip2); // expected-error{{incompatible pointer types passing 'int *' to parameter of type 'float *'}}
 
-  int *ip3 = [overridden // expected-warning{{incompatible pointer types initializing 'int *' with an expression of type 'char *'}}
-                methodToMangle: ip3 // expected-warning{{incompatible pointer types sending 'int *' to parameter of type 'double *'}}
-                        second: ip3]; // expected-warning{{incompatible pointer types sending 'int *' to parameter of type 'float *'}}
+  int *ip3 = [overridden // expected-error{{incompatible pointer types initializing 'int *' with an expression of type 'char *'}}
+                methodToMangle: ip3 // expected-error{{incompatible pointer types sending 'int *' to parameter of type 'double *'}}
+                        second: ip3]; // expected-error{{incompatible pointer types sending 'int *' to parameter of type 'float *'}}
 
-  int *ip4 = overridden.intPropertyToMangle; // expected-warning{{incompatible pointer types initializing 'int *' with an expression of type 'double *'}}
+  int *ip4 = overridden.intPropertyToMangle; // expected-error{{incompatible pointer types initializing 'int *' with an expression of type 'double *'}}
 }
 
 // expected-note@SomeKit/SomeKit.h:42{{passing argument to parameter 'ptr' here}}

clang/test/AST/ByteCode/atomic.c

@@ -8,8 +8,8 @@ _Atomic int ai = 0;
 // FIXME: &ai is an address constant, so this should be accepted as an
 // initializer, but the bit-cast inserted due to the pointer conversion is
 // tripping up the test for whether the initializer is a constant expression.
-// The warning is correct but the error is not.
-_Atomic(int *) aip3 = &ai; // both-warning {{incompatible pointer types initializing '_Atomic(int *)' with an expression of type '_Atomic(int) *'}} \
+// The first error is correct; the second is not.
+_Atomic(int *) aip3 = &ai; // both-error {{incompatible pointer types initializing '_Atomic(int *)' with an expression of type '_Atomic(int) *'}} \
                            // both-error {{initializer element is not a compile-time constant}}
 
 #include <stdatomic.h>

clang/test/AST/ByteCode/c.c

@@ -349,7 +349,7 @@ const unsigned char _str2[] = {S[0], S[1], S[2], S[3], S[4], S[5], S[6], S[7]};
 const int compared = strcmp(_str, (const char *)_str2); // all-error {{initializer element is not a compile-time constant}}
 
 
-const int compared2 = strcmp(strcmp, _str); // all-warning {{incompatible pointer types}} \
+const int compared2 = strcmp(strcmp, _str); // all-error {{incompatible pointer types}} \
                                             // all-error {{initializer element is not a compile-time constant}}
 
 int foo(x) // all-warning {{a function definition without a prototype is deprecated in all versions of C}}

clang/test/Analysis/OSAtomic_mac.c

@@ -15,7 +15,7 @@ int *invalidSLocOnRedecl(void) {
   // something like "The "compare" part of CompareAndSwap depends on an
   // undefined value".
   int *b;
-  OSAtomicCompareAndSwapPtrBarrier(0, 0, &b); // no-crash
+  OSAtomicCompareAndSwapPtrBarrier(0, 0, (void**)&b); // no-crash
   return b;
 }
 

clang/test/Analysis/bsd-string.c

@@ -137,5 +137,5 @@ void f11(void) {
 int a, b;
 void unknown_val_crash(void) {
   // We're unable to evaluate the integer-to-pointer cast.
-  strlcat(&b, a, 0); // no-crash
+  strlcat((char*)&b, a, 0); // no-crash
 }