[clang][bytecode] Fix null Descriptor dereference in ArrayElemPtrPop #163386
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ByteCode interpretor could deref a null descriptor when handling typeid (or function pointers) in ArrayElemPtrPop. We need to treat this case as having no descriptor
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llvmbot
added
clang
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@llvm/pr-subscribers-clang Author: None (term-est) ChangesFixes #163127 Do we need to add a regression test? I can add something like // RUN: %clang_cc1 -std=c++20 -fexperimental-new-constant-interpreter -verify=both,expected %s
// RUN: %clang_cc1 -std=c++20 -verify=both,ref %s
// both-no-diagnostics
bool f() {
return ((void**)&typeid(int))[0];
}to clang/tests/AST/bytecode. Let me know Full diff: https://github.com/llvm/llvm-project/pull/163386.diff 1 Files Affected:
diff --git a/clang/lib/AST/ByteCode/Interp.h b/clang/lib/AST/ByteCode/Interp.h
index 57cc705282d1b..7b177f3a9fdb7 100644
--- a/clang/lib/AST/ByteCode/Interp.h
+++ b/clang/lib/AST/ByteCode/Interp.h
@@ -3126,7 +3126,8 @@ inline bool ArrayElemPtrPop(InterpState &S, CodePtr OpPC) {
}
if (Offset.isZero()) {
- if (Ptr.getFieldDesc()->isArray() && Ptr.getIndex() == 0) {
+ if (const Descriptor *Desc = Ptr.getFieldDesc();
+ Desc && Desc->isArray() && Ptr.getIndex() == 0) {
S.Stk.push<Pointer>(Ptr.atIndex(0).narrow());
return true;
}
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Yes, we do need a test please. |
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Added a test case, it fails prior to the 7e74074 and passes properly afterwards. |
tbaederr
changed the title
tbaederr
reviewed
Oct 15, 2025
| if (Offset.isZero()) { | ||
| if (Ptr.getFieldDesc()->isArray() && Ptr.getIndex() == 0) { | ||
| if (const Descriptor *Desc = Ptr.getFieldDesc(); | ||
| Desc && Desc->isArray() && Ptr.getIndex() == 0) { |
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You need to do the same change in ArrayElemPtr above.
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added with dae76b1
Do you think we need this kind of check for each use of getFieldDesc? Or the other uses are not supposed to be null
If so, I think we need some assertions
tbaederr
approved these changes
Oct 15, 2025
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/72/builds/15499 Here is the relevant piece of the build log for the reference |
shafik
reviewed
Oct 17, 2025
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Thank you for the fix, since no one mentioned it in the review, it looks like Timm took care of it when he merged but I wanted to mention it to you for the future.
The summary is normally what goes into the git log and so what is there should cover
- A description of the problem
- A description of the solution
- A description of other important details like specific algorithms or design choices
Any questions should be made as comments to the PR and they can be addressed as replies.
Hello shafik~ For future reference, do you mind giving me some I had this for the commit message, was it problematic :/ |
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Fixes #163127
Do we need to add a regression test? I can add something like
to clang/tests/AST/bytecode. Let me know