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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Life time issue with const reference to temporary"
href="https://bugs.llvm.org/show_bug.cgi?id=32098">32098</a>
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<th>Summary</th>
<td>Life time issue with const reference to temporary
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>4.0
</td>
</tr>
<tr>
<th>Hardware</th>
<td>All
</td>
</tr>
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<th>OS</th>
<td>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>release blocker
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>C++11
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>stevenwu@apple.com
</td>
</tr>
<tr>
<th>CC</th>
<td>dgregor@apple.com, llvm-bugs@lists.llvm.org
</td>
</tr></table>
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<pre>Here is the test case:
$ cat test.cpp
class A {
public:
A(int v) { _a = v; }
A& check() { return *this; }
static int getV(A x) { return x._a; }
int _a;
};
A test() {
return A(0);
}
int main() {
const A& x = test().check();
int ret = A::getV(x);
return ret;
}
$ clang++ --std=c++11 -Os test.cpp -mllvm -disable-llvm-optzns -emit-llvm -S -o
-
define i32 @main() #1 {
%1 = alloca i32, align 4
%2 = alloca %class.A*, align 8
%3 = alloca %class.A, align 4
%4 = alloca i32, align 4
%5 = alloca %class.A, align 4
store i32 0, i32* %1, align 4
%6 = bitcast %class.A** %2 to i8*
call void @llvm.lifetime.start(i64 8, i8* %6) #5
%7 = bitcast %class.A* %3 to i8*
call void @llvm.lifetime.start(i64 4, i8* %7) #5
%8 = call i32 @_Z4testv() #4
%9 = getelementptr inbounds %class.A, %class.A* %3, i32 0, i32 0
store i32 %8, i32* %9, align 4
%10 = call dereferenceable(4) %class.A* @_ZN1A5checkEv(%class.A* %3) #4
%11 = bitcast %class.A* %3 to i8*
call void @llvm.lifetime.end(i64 4, i8* %11) #5
store %class.A* %10, %class.A** %2, align 8, !tbaa !8
%12 = bitcast i32* %4 to i8*
call void @llvm.lifetime.start(i64 4, i8* %12) #5
%13 = load %class.A*, %class.A** %2, align 8
%14 = bitcast %class.A* %5 to i8*
%15 = bitcast %class.A* %13 to i8*
call void @llvm.memcpy.p0i8.p0i8.i64(i8* %14, i8* %15, i64 4, i32 4, i1
false), !tbaa.struct !9
%16 = getelementptr inbounds %class.A, %class.A* %5, i32 0, i32 0
%17 = load i32, i32* %16, align 4
%18 = call i32 @_ZN1A4getVES_(i32 %17) #4
store i32 %18, i32* %4, align 4, !tbaa !6
%19 = load i32, i32* %4, align 4, !tbaa !6
%20 = bitcast i32* %4 to i8*
call void @llvm.lifetime.end(i64 4, i8* %20) #5
%21 = bitcast %class.A** %2 to i8*
call void @llvm.lifetime.end(i64 8, i8* %21) #5
ret i32 %19
}
The lifetime intrinsics suggests that "const A& x" dies immediately after the
expression which I am not sure if that is the correct behavior. This will cause
crashes if test and check function are not inlined.
This looks like a regression after r288563.</pre>
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