r310672 - [Sema][ObjC] Fix spurious -Wcast-qual warnings.

[Hans Wennborg via cfe-commits]

Okay, merged in r311095.

On Tue, Aug 15, 2017 at 11:50 AM, Akira Hatanaka <ahatanaka at apple.com> wrote:
> Hans, is it okay to merge this to 5.0?
>
>> On Aug 10, 2017, at 5:06 PM, Akira Hatanaka via cfe-commits <cfe-commits at lists.llvm.org> wrote:
>>
>> Author: ahatanak
>> Date: Thu Aug 10 17:06:49 2017
>> New Revision: 310672
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=310672&view=rev
>> Log:
>> [Sema][ObjC] Fix spurious -Wcast-qual warnings.
>>
>> We do not meaningfully track object const-ness of Objective-C object
>> types. Silence the -Wcast-qual warning that is issued when casting to or
>> from Objective-C object types results in losing const qualification.
>>
>> rdar://problem/33807915
>>
>> Modified:
>>    cfe/trunk/lib/Sema/SemaCast.cpp
>>    cfe/trunk/test/SemaObjC/illegal-nonarc-bridged-cast.m
>>
>> Modified: cfe/trunk/lib/Sema/SemaCast.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaCast.cpp?rev=310672&r1=310671&r2=310672&view=diff
>> ==============================================================================
>> --- cfe/trunk/lib/Sema/SemaCast.cpp (original)
>> +++ cfe/trunk/lib/Sema/SemaCast.cpp Thu Aug 10 17:06:49 2017
>> @@ -552,7 +552,14 @@ CastsAwayConstness(Sema &Self, QualType
>>     Qualifiers SrcQuals, DestQuals;
>>     Self.Context.getUnqualifiedArrayType(UnwrappedSrcType, SrcQuals);
>>     Self.Context.getUnqualifiedArrayType(UnwrappedDestType, DestQuals);
>> -
>> +
>> +    // We do not meaningfully track object const-ness of Objective-C object
>> +    // types. Remove const from the source type if either the source or
>> +    // the destination is an Objective-C object type.
>> +    if (UnwrappedSrcType->isObjCObjectType() ||
>> +        UnwrappedDestType->isObjCObjectType())
>> +      SrcQuals.removeConst();
>> +
>>     Qualifiers RetainedSrcQuals, RetainedDestQuals;
>>     if (CheckCVR) {
>>       RetainedSrcQuals.setCVRQualifiers(SrcQuals.getCVRQualifiers());
>>
>> Modified: cfe/trunk/test/SemaObjC/illegal-nonarc-bridged-cast.m
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaObjC/illegal-nonarc-bridged-cast.m?rev=310672&r1=310671&r2=310672&view=diff
>> ==============================================================================
>> --- cfe/trunk/test/SemaObjC/illegal-nonarc-bridged-cast.m (original)
>> +++ cfe/trunk/test/SemaObjC/illegal-nonarc-bridged-cast.m Thu Aug 10 17:06:49 2017
>> @@ -1,8 +1,9 @@
>> -// RUN: %clang_cc1 -triple x86_64-apple-darwin11 -fsyntax-only -fblocks -verify %s
>> +// RUN: %clang_cc1 -triple x86_64-apple-darwin11 -fsyntax-only -fblocks -Wcast-qual -verify %s
>> // rdar://10597832
>>
>> typedef const void *CFTypeRef;
>> typedef const struct __CFString *CFStringRef;
>> + at class NSString;
>>
>> @interface NSString
>> @end
>> @@ -18,7 +19,7 @@ NSString *CreateNSString();
>> void from_cf() {
>>   id obj1 = (__bridge_transfer id)CFCreateSomething(); // expected-warning {{'__bridge_transfer' casts have no effect when not using ARC}}
>>   id obj2 = (__bridge_transfer NSString*)CFCreateString(); // expected-warning {{'__bridge_transfer' casts have no effect when not using ARC}}
>> -  (__bridge int*)CFCreateSomething(); // expected-warning {{expression result unused}}
>> +  (__bridge int*)CFCreateSomething(); // expected-warning {{expression result unused}} expected-warning {{cast from 'const void *' to 'int *' drops const qualifier}}
>>   id obj3 = (__bridge id)CFGetSomething();
>>   id obj4 = (__bridge NSString*)CFGetString();
>> }
>> @@ -41,3 +42,15 @@ void to_cf_ignored(id obj) {
>>   CFTypeRef cf1 = (__bridge_retained CFTypeRef)CreateSomething(); // no-warning
>>   CFTypeRef cf3 = (__bridge CFTypeRef)CreateSomething(); // no-warning
>> }
>> +
>> +// Check that clang doesn't warn about dropping const from Objective-C object
>> +// types.
>> +void test_wcast_qual() {
>> +  CFStringRef c;
>> +  NSString *n0 = (NSString *)c;
>> +  NSString **n1 = (NSString **)&c;
>> +  const NSString *n2;
>> +  const NSString **n3;
>> +  void *p0 = (void *)n2;
>> +  void **p1 = (void **)n3;
>> +}
>>
>>
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