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<base href="https://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [WinEH] no-return function in cleanup code not called with -O"
href="https://llvm.org/bugs/show_bug.cgi?id=25997">25997</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>[WinEH] no-return function in cleanup code not called with -O
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Windows XP
</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>LLVM Codegen
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>r.sagitario@gmx.de
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>This code:
#include <stdlib.h>
#include <stdio.h>
struct Cleanup
{
~Cleanup()
{
puts("abort");
exit(42);
}
};
void test()
{
try
{
Cleanup a;
throw int(3);
}
catch(int)
{
}
}
int main(int argc, char** argv)
{
test();
}
compiles and runs correctly (prints "abort" and has exit code 42) when built
with "clang -fexceptions -m32". Adding "-O" to the command line causes the
program to crash.
The C++ code itself seems questionable, but other languages support arbitrary
code in "finally" blocks, e.g. throwing another exception.
The IR for the test function:
define void @"\01?test@@YAXXZ"() #0 personality i8* bitcast (i32 (...)*
@__CxxFrameHandler3 to i8*) {
entry:
%a = alloca %struct.Cleanup, align 1
%tmp = alloca i32, align 4
store i32 3, i32* %tmp, align 4
%0 = bitcast i32* %tmp to i8*
invoke void @_CxxThrowException(i8* %0, %eh.ThrowInfo* @_TI1H) #4
to label %unreachable unwind label %ehcleanup
ehcleanup: ; preds = %entry
%1 = cleanuppad within none []
call x86_thiscallcc void @"\01??1Cleanup@@QAE@XZ"(%struct.Cleanup* %a) #5 [
"funclet"(token %1) ]
cleanupret from %1 unwind label %catch.dispatch
catch.dispatch: ; preds = %ehcleanup
%2 = catchswitch within none [label %catch] unwind to caller
catch: ; preds = %catch.dispatch
%3 = catchpad within %2 [%rtti.TypeDescriptor2* @"\01??_R0H@8", i32 0, i8*
null]
catchret from %3 to label %catchret.dest
catchret.dest: ; preds = %catch
br label %try.cont
try.cont: ; preds = %catchret.dest
ret void
unreachable: ; preds = %entry
unreachable
}
The problem here is that the optimizer infers "noreturn" from the cleanup call
and replaces "cleanupret" with "unreachable":
define void @"\01?test@@YAXXZ"() #0 personality i8* bitcast (i32 (...)*
@__CxxFrameHandler3 to i8*) {
entry:
%a = alloca %struct.Cleanup, align 1
%tmp = alloca i32, align 4
%0 = getelementptr inbounds %struct.Cleanup, %struct.Cleanup* %a, i32 0, i32
0
call void @llvm.lifetime.start(i64 1, i8* %0) #6
store i32 3, i32* %tmp, align 4, !tbaa !4
%1 = bitcast i32* %tmp to i8*
invoke void @_CxxThrowException(i8* %1, %eh.ThrowInfo* nonnull @_TI1H) #7
to label %unreachable unwind label %ehcleanup
ehcleanup: ; preds = %entry
%2 = cleanuppad within none []
call x86_thiscallcc void @"\01??1Cleanup@@QAE@XZ"(%struct.Cleanup* nonnull
%a) #6 [ "funclet"(token %2) ]
unreachable
unreachable: ; preds = %entry
unreachable
}
This seems to break the funclet extraction mechanism for the Windows exception
handling.</pre>
</div>
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