[PATCH] D84455: [Concepts] Fix a deserialization crash.

[Haojian Wu via Phabricator via cfe-commits]

hokein created this revision.
hokein added a reviewer: rsmith.
Herald added a subscriber: kristof.beyls.
Herald added a project: clang.

`TemplateTypeParmDecl::hasTypeConstraint` is not a safe guard for
checking `TemplateTypeParmDecl::getTypeConstraint()` result is null.

in somecases (e.g. implicit deduction guide templates synthesized from the
constructor), hasTypeConstraint returns false, and getTypeConstraint
returns a nullptr.

Fix https://bugs.llvm.org/show_bug.cgi?id=46790


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D84455

Files:
  clang/lib/Serialization/ASTReaderDecl.cpp
  clang/test/PCH/cxx2a-constraints-crash.cpp


Index: clang/test/PCH/cxx2a-constraints-crash.cpp
===================================================================
--- /dev/null
+++ clang/test/PCH/cxx2a-constraints-crash.cpp
@@ -0,0 +1,29 @@
+// RUN: %clang_cc1 -std=c++2a -emit-pch %s -o %t
+// RUN: %clang_cc1 -std=c++2a -include-pch %t -verify %s
+
+// expected-no-diagnostics
+
+#ifndef HEADER
+#define HEADER
+
+template <typename T, typename U>
+concept not_same_as = true;
+
+template <int Kind>
+struct subrange {
+  template <not_same_as<int> R>
+  subrange(R) requires(Kind == 0);
+
+  template <not_same_as<int> R>
+  subrange(R) requires(Kind != 0);
+};
+
+template <typename R>
+subrange(R) -> subrange<42>;
+
+int main() {
+  int c;
+  subrange s(c);
+}
+
+#endif
\ No newline at end of file
Index: clang/lib/Serialization/ASTReaderDecl.cpp
===================================================================
--- clang/lib/Serialization/ASTReaderDecl.cpp
+++ clang/lib/Serialization/ASTReaderDecl.cpp
@@ -2909,9 +2909,11 @@
       return false;
     if (TX->hasTypeConstraint() != TY->hasTypeConstraint())
       return false;
-    if (TX->hasTypeConstraint()) {
-      const TypeConstraint *TXTC = TX->getTypeConstraint();
-      const TypeConstraint *TYTC = TY->getTypeConstraint();
+    const TypeConstraint *TXTC = TX->getTypeConstraint();
+    const TypeConstraint *TYTC = TY->getTypeConstraint();
+    if (!TXTC != !TYTC)
+      return false;
+    if (TXTC && TYTC) {
       if (TXTC->getNamedConcept() != TYTC->getNamedConcept())
         return false;
       if (TXTC->hasExplicitTemplateArgs() != TYTC->hasExplicitTemplateArgs())


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