[LLVMbugs] [Bug 4180] New: MDNodes may be used after being destroyed
bugzilla-daemon at cs.uiuc.edu
bugzilla-daemon at cs.uiuc.edu
Fri May 8 05:09:28 PDT 2009
http://llvm.org/bugs/show_bug.cgi?id=4180
Summary: MDNodes may be used after being destroyed
Product: new-bugs
Version: unspecified
Platform: PC
OS/Version: Linux
Status: NEW
Severity: normal
Priority: P2
Component: new bugs
AssignedTo: unassignedbugs at nondot.org
ReportedBy: fvbommel at wxs.nl
CC: llvmbugs at cs.uiuc.edu
Created an attachment (id=2975)
--> (http://llvm.org/bugs/attachment.cgi?id=2975)
Valgrind output for example program
I'm seeing crashes due to invalid pointer accesses from
==24533== at 0x498DDF:
llvm::FoldingSetImpl::FindNodeOrInsertPos(llvm::FoldingSetNodeID const&,
void*&) (in /home/urxae/tmp/llvm-test/mdnode/test)
==24533== by 0x40C9C1: llvm::MDNode::get(llvm::Constant* const*, unsigned)
(in /home/urxae/tmp/llvm-test/mdnode/test)
These seem to be because MDNodes don't get removed from the MDNodeSet global
upon destruction.
I'm attaching full valgrind output for the following program:
=====
#include "llvm/Module.h"
#include "llvm/Type.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Constants.h"
#include "llvm/GlobalVariable.h"
using namespace llvm;
int main() {
const Type* Ty = Type::Int32Ty;
char buf[20];
const unsigned MAX = 100;
for (unsigned i = 0; i < MAX; i++) {
snprintf(buf, 20, "var_%u", i);
Module* M = new Module("test");
Constant* vals[] = {
new GlobalVariable(Ty, true, GlobalValue::WeakODRLinkage,
UndefValue::get(Ty), buf, M),
};
Constant* node = MDNode::get(vals, sizeof(vals) / sizeof(vals[0]));
delete M;
}
return 0;
}
=====
(If you can't reproduce, try increasing the loop count)
The patch is extremely trivial, once problem is diagnosed:
######
Index: lib/VMCore/Constants.cpp
===================================================================
--- lib/VMCore/Constants.cpp (revision 71118)
+++ lib/VMCore/Constants.cpp (working copy)
@@ -1714,6 +1714,7 @@
}
void MDNode::destroyConstant() {
+ MDNodeSet->RemoveNode(this);
destroyConstantImpl();
}
######
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