https://github.com/shashi1687 created
https://github.com/llvm/llvm-project/pull/147213
### Summary
Briefly what this PR does, in one or two sentences.
> Filters out invalid (null) base-specifiers in `ActOnBaseSpecifiers()`,
> preventing ICEs on incomplete or non-class bases.
### Motivation
Why this change is needed.
> When you inherit from a forward‐declared class or non-class type, Sema used
> to emit an error _and_ still hand the bad pointer to later code, causing an
> internal compiler error. We now drop those invalid entries immediately.
### Root Cause Analysis
A very short bulleted “root cause.”
- `ActOnBaseSpecifier` returns `nullptr` for invalid bases.
- `ActOnBaseSpecifiers` passed **all** pointers (including null) to
`AttachBaseSpecifiers`.
- Later layout or special‐member lookup on null caused the ICE.
### Changes in this PR
List the key files and rough diff summary.
- **clang/lib/Sema/SemaDeclCXX.cpp**
- In `ActOnBaseSpecifiers()`, gather `Bases` into a `SmallVector`, skipping
null entries.
- **clang/test/SemaCXX/invalid-base-inheritance.cpp**
- New regression test checking for the proper diagnostics and that no ICE
occurs.
### Test Plan
How you verified the change.
1. **Local build/test**
```bash
mkdir build && cd build
cmake -G Ninja ../llvm \
-DLLVM_ENABLE_PROJECTS="clang" \
-DCMAKE_BUILD_TYPE=Release
ninja clang
ninja check-clang
>From 36559cab1bce1bbd8b501521c6c252d6d3fa00ce Mon Sep 17 00:00:00 2001
From: Shashi Shankar <shashishankar1...@gmail.com>
Date: Sun, 6 Jul 2025 22:25:48 +0200
Subject: [PATCH] Sema: filter out invalid base-specifiers before attaching
ActOnBaseSpecifiers now skips nullptr entries returned for invalid bases,
avoiding ICE on invalid inheritance. Added regression test in
SemaCXX/invalid-inheritance.cpp.
Signed-off-by: Shashi Shankar <shashishankar1...@gmail.com>
---
clang/lib/Sema/SemaDeclCXX.cpp | 17 ++++++++++++++++-
clang/test/SemaCXX/invalid-base-inheritance.cpp | 17 +++++++++++++++++
2 files changed, 33 insertions(+), 1 deletion(-)
create mode 100644 clang/test/SemaCXX/invalid-base-inheritance.cpp
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index f0247f865ba40..231610241d8ee 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -3031,8 +3031,23 @@ void Sema::ActOnBaseSpecifiers(Decl *ClassDecl,
if (!ClassDecl || Bases.empty())
return;
+ // --- drop any bases already diagnosed invalid ---
+ SmallVector<CXXBaseSpecifier *, 4> ValidBases;
+ ValidBases.reserve(Bases.size());
+ for (auto *BS : Bases)
+ if (BS)
+ ValidBases.push_back(BS);
+ if (ValidBases.empty())
+ return;
+
+ if (ValidBases.empty())
+ return; // nothing valid to attach
+
AdjustDeclIfTemplate(ClassDecl);
- AttachBaseSpecifiers(cast<CXXRecordDecl>(ClassDecl), Bases);
+ // Attach only the valid bases so downstream never ICEs
+ AttachBaseSpecifiers(cast<CXXRecordDecl>(ClassDecl),
+ llvm::MutableArrayRef<CXXBaseSpecifier *>(
+ ValidBases.data(), ValidBases.size()));
}
bool Sema::IsDerivedFrom(SourceLocation Loc, CXXRecordDecl *Derived,
diff --git a/clang/test/SemaCXX/invalid-base-inheritance.cpp
b/clang/test/SemaCXX/invalid-base-inheritance.cpp
new file mode 100644
index 0000000000000..e37b77bcd3fea
--- /dev/null
+++ b/clang/test/SemaCXX/invalid-base-inheritance.cpp
@@ -0,0 +1,17 @@
+// Tests that invalid base-specifiers no longer crash the compiler.
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+class X; // forward declaration
+
+class A : X { // incomplete base → error, but no ICE
+ // expected-error@-1 {{base class has incomplete type}}
+};
+
+class Y : int { // base not a class → error, but no ICE
+ // expected-error@-1 {{expected class name}}
+};
+
+class Z : X*, virtual int { // mixed invalid specifiers
+ // expected-error@-2 {{base class has incomplete type}}
+ // expected-error@-1 {{expected class name}}
+};
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