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Fix wrong strong layout result because of unaligned instance start. #102

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Fix wrong strong layout result because of unaligned instance start. #102

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3aa1b9c
Fix wrong strong layout result because of unaligned instance start.
Nov 9, 2020
c169f37
Merge branch 'master' into master
pudge62 Dec 22, 2020
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3 changes: 2 additions & 1 deletion FBRetainCycleDetector/Layout/Classes/FBClassStrongLayout.mm
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Original file line number Diff line number Diff line change
Expand Up @@ -146,7 +146,8 @@ static NSUInteger FBGetMinimumIvarIndex(__unsafe_unretained Class aCls) {
if (count > 0) {
Ivar ivar = ivars[0];
ptrdiff_t offset = ivar_getOffset(ivar);
minimumIndex = offset / (sizeof(void *));
// unaligned bytes at the start of this class's ivars are not represented in the layout bitmap.
minimumIndex = (offset + (sizeof(void *) - 1)) / (sizeof(void *));
}

free(ivars);
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24 changes: 24 additions & 0 deletions FBRetainCycleDetectorTests/FBClassStrongLayoutTests.mm
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Expand Up @@ -13,6 +13,7 @@

#import <FBRetainCycleDetector/FBClassStrongLayout.h>
#import <FBRetainCycleDetector/FBRetainCycleDetector.h>
#import <FBRetainCycleDetector/FBObjectReference.h>

@interface _RCDTestEmptyClass : NSObject
@end
Expand Down Expand Up @@ -157,6 +158,22 @@ @implementation _RCDTestClassWithCppStructAndStrongProperty
}
@end

@interface _RCDTestClassWithUnalignEndIvar : NSObject {
char content[20];
}
@end
@implementation _RCDTestClassWithUnalignEndIvar
@end

@interface _RCDTestClassWithUnalignEndIvarParentClass : _RCDTestClassWithUnalignEndIvar {
int integer;
__weak NSObject *object1;
NSObject *object2;
}
@end
@implementation _RCDTestClassWithUnalignEndIvarParentClass
@end

@interface FBClassStrongLayoutTests : XCTestCase
@end

Expand Down Expand Up @@ -260,4 +277,11 @@ - (void)testLayoutForClassWithCppStructAndStrongPropertyWillNotCrashAndFetchStro
XCTAssertEqual([ivars count], 1);
}

- (void)testLayoutForClassWithParentClassHasUnalignEndIvar
{
NSArray<id<FBObjectReference>> *ivars = FBGetObjectStrongReferences([_RCDTestClassWithUnalignEndIvarParentClass new], nil);
XCTAssertEqual([ivars count], 1);
XCTAssertEqualObjects([[ivars firstObject] namePath], @[@"object2"]);
}

@end