[PATCH] D33606: [Sema] Fix a crash-on-invalid when a template parameter list has a class definition or non-reference class type

[Akira Hatanaka via Phabricator via cfe-commits]

ahatanak created this revision.

Currently clang crashes with an assertion failure in SemaAccess.cpp ("Assertion failed: (Access == AS_private || Access == AS_protected)") when compiling the following invalid code:

  class C0 {
  public:
    template<typename T0, typename T1 = T0 // missing closing angle bracket
    struct S0 {};
  
    C0() : m(new S0<int>) {}
    S0<int> *m;
  
    template<class C1 *p>
    void foo1();
  };
  
  C1 *x;

This seems to happen because:

- The definition of struct S0 is parsed as part of the template parameters list because of the missing closing angle bracket.
- Sema adds struct S0 to class C0's scope. But if struct S0 is introduced in a template parameter list, it should add the struct to the enclosing scope (the file scope), just like it would add class C1 to the file scope.
- It looks up S0 in C0's scope and then checks its access specifier when LookupResult is destructed. The assertion fails because S0's access specifier is not set (it's AS_none).

To fix the crash, I made changes in Sema::ActOnTag to check whether it's parsing a template parameter list and, if it is, move S0 to the correct scope. Also, the TagDecl is marked as invalid if the class is defined in a template parameter list. Note that test/SemaCXX/PR16677.cpp loses one error diagnostic because of this change.

rdar://problem/31783961
rdar://problem/19570630


https://reviews.llvm.org/D33606

Files:
  include/clang/Parse/Parser.h
  include/clang/Sema/Sema.h
  lib/Parse/ParseDecl.cpp
  lib/Parse/ParseDeclCXX.cpp
  lib/Parse/ParseTemplate.cpp
  lib/Sema/SemaDecl.cpp
  lib/Sema/SemaDeclCXX.cpp
  lib/Sema/SemaTemplate.cpp
  test/SemaCXX/PR16677.cpp
  test/SemaCXX/invalid-template-params.cpp

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