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<base href="http://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - ARC optimizer prematurely releases result of ternary operator when assigning to __attribute__(objc_precise_lifetime) variable"
href="http://llvm.org/bugs/show_bug.cgi?id=17778">17778</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>ARC optimizer prematurely releases result of ternary operator when assigning to __attribute__(objc_precise_lifetime) variable
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>3.3
</td>
</tr>
<tr>
<th>Hardware</th>
<td>All
</td>
</tr>
<tr>
<th>OS</th>
<td>MacOS X
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>-New Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>bgertzfield@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=11474" name="attach_11474" title="Repro case for bug">attachment 11474</a> <a href="attachment.cgi?id=11474&action=edit" title="Repro case for bug">[details]</a></span>
Repro case for bug
These two statements perform identically with -O0:
__attribute__((objc_precise_lifetime)) Scoped *scoped1 = [[Scoped alloc] init];
__attribute__((objc_precise_lifetime)) Scoped *scoped2 = DoSomeCheck() ?
[[Scoped alloc] init] : nil;
However, with -O1 or higher, the second statement releases the object before
assigning it to 'scoped2'. Attached test case reproduces issue:
2013-11-01 16:53:13.479 testARC-opt[85825:707] -[Scoped init] <Scoped:
0x7ff758c081a0>
2013-11-01 16:53:13.484 testARC-opt[85825:707] At the end of first block
2013-11-01 16:53:13.485 testARC-opt[85825:707] -[Scoped dealloc] <Scoped:
0x7ff758c081a0>
2013-11-01 16:53:13.486 testARC-opt[85825:707] -[Scoped init] <Scoped:
0x7ff759b00470>
2013-11-01 16:53:13.486 testARC-opt[85825:707] -[Scoped dealloc] <Scoped:
0x7ff759b00470>
2013-11-01 16:53:13.487 testARC-opt[85825:707] At the end of second block
Interestingly, the following statements behave the same as the first statement,
suggesting it's not just the ternary operator at fault:
Scoped *scopeMe = DoSomeCheck() ? [[Scoped alloc] init] : nil;
__attribute__((objc_precise_lifetime)) Scoped *scoped3 = scopeMe;
Reproduced in Clang 3.3 as shipped with Xcode 5.0 (5A1412).
% clang -v
Apple LLVM version 5.0 (clang-500.2.75) (based on LLVM 3.3svn)
Target: x86_64-apple-darwin12.4.0
Thread model: posix
% cat testARC.m
#import <Foundation/Foundation.h>
static BOOL gSomeValue;
static BOOL DoSomeCheck(void)
{
return gSomeValue;
}
@interface Scoped : NSObject
@end
@implementation Scoped
- (instancetype)init
{
self = [super init];
NSLog(@"%s %@", __func__, self);
return self;
}
- (void)dealloc
{
NSLog(@"%s %@", __func__, self);
}
@end
int main(int argc, char **argv)
{
gSomeValue = YES;
{
__attribute__((objc_precise_lifetime)) Scoped *scoped = [[Scoped alloc]
init];
NSLog(@"At the end of first block");
}
{
__attribute__((objc_precise_lifetime)) Scoped *scoped = DoSomeCheck() ?
[[Scoped alloc] init] : nil;
NSLog(@"At the end of second block");
}
{
Scoped *scopeMe = DoSomeCheck() ? [[Scoped alloc] init] : nil;
__attribute__((objc_precise_lifetime)) Scoped *scoped = scopeMe;
NSLog(@"At the end of third block");
}
}
% clang -fobjc-arc -O0 -o testARC-dbg ./testARC.m
% clang -fobjc-arc -Os -o testARC-opt ./testARC.m
% ./testARC-dbg
2013-11-01 16:53:27.387 testARC-dbg[85843:707] -[Scoped init] <Scoped:
0x7f9102c081c0>
2013-11-01 16:53:27.389 testARC-dbg[85843:707] At the end of first block
2013-11-01 16:53:27.389 testARC-dbg[85843:707] -[Scoped dealloc] <Scoped:
0x7f9102c081c0>
2013-11-01 16:53:27.390 testARC-dbg[85843:707] -[Scoped init] <Scoped:
0x7f9103b009d0>
2013-11-01 16:53:27.390 testARC-dbg[85843:707] At the end of second block
2013-11-01 16:53:27.390 testARC-dbg[85843:707] -[Scoped dealloc] <Scoped:
0x7f9103b009d0>
2013-11-01 16:53:27.391 testARC-dbg[85843:707] -[Scoped init] <Scoped:
0x7f9102c02b40>
2013-11-01 16:53:27.408 testARC-dbg[85843:707] At the end of third block
2013-11-01 16:53:27.412 testARC-dbg[85843:707] -[Scoped dealloc] <Scoped:
0x7f9102c02b40>
% ./testARC-opt
2013-11-01 16:53:13.479 testARC-opt[85825:707] -[Scoped init] <Scoped:
0x7ff758c081a0>
2013-11-01 16:53:13.484 testARC-opt[85825:707] At the end of first block
2013-11-01 16:53:13.485 testARC-opt[85825:707] -[Scoped dealloc] <Scoped:
0x7ff758c081a0>
2013-11-01 16:53:13.486 testARC-opt[85825:707] -[Scoped init] <Scoped:
0x7ff759b00470>
2013-11-01 16:53:13.486 testARC-opt[85825:707] -[Scoped dealloc] <Scoped:
0x7ff759b00470>
2013-11-01 16:53:13.487 testARC-opt[85825:707] At the end of second block
2013-11-01 16:53:13.489 testARC-opt[85825:707] -[Scoped init] <Scoped:
0x7ff759900140>
2013-11-01 16:53:13.489 testARC-opt[85825:707] At the end of third block
2013-11-01 16:53:13.490 testARC-opt[85825:707] -[Scoped dealloc] <Scoped:
0x7ff759900140></pre>
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