[clang] e69138d - PR46859: Fix crash if declaring a template in a DeclScope with no DeclContext.

[Richard Smith via cfe-commits]

Author: Richard Smith
Date: 2020-07-29T12:02:55-07:00
New Revision: e69138dad5a535c4027a1931f05cabab0f484974

URL: https://github.com/llvm/llvm-project/commit/e69138dad5a535c4027a1931f05cabab0f484974
DIFF: https://github.com/llvm/llvm-project/commit/e69138dad5a535c4027a1931f05cabab0f484974.diff

LOG: PR46859: Fix crash if declaring a template in a DeclScope with no DeclContext.

This can happen during error recovery; it could also happen at block
scope if we ever parsed a template declaration at block scope.

Added: 
    

Modified: 
    clang/lib/Sema/SemaTemplate.cpp
    clang/test/SemaCXX/extern-c.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index c05ed0b14e3e..76ba12303d84 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -7774,15 +7774,14 @@ Sema::CheckTemplateDeclScope(Scope *S, TemplateParameterList *TemplateParams) {
   // C++ [temp]p4:
   //   A template [...] shall not have C linkage.
   DeclContext *Ctx = S->getEntity();
-  assert(Ctx && "Unknown context");
-  if (Ctx->isExternCContext()) {
+  if (Ctx && Ctx->isExternCContext()) {
     Diag(TemplateParams->getTemplateLoc(), diag::err_template_linkage)
         << TemplateParams->getSourceRange();
     if (const LinkageSpecDecl *LSD = Ctx->getExternCContext())
       Diag(LSD->getExternLoc(), diag::note_extern_c_begins_here);
     return true;
   }
-  Ctx = Ctx->getRedeclContext();
+  Ctx = Ctx ? Ctx->getRedeclContext() : nullptr;
 
   // C++ [temp]p2:
   //   A template-declaration can appear only as a namespace scope or

diff  --git a/clang/test/SemaCXX/extern-c.cpp b/clang/test/SemaCXX/extern-c.cpp
index 1a32beec7baa..68d1494b9491 100644
--- a/clang/test/SemaCXX/extern-c.cpp
+++ b/clang/test/SemaCXX/extern-c.cpp
@@ -259,3 +259,8 @@ namespace PR35697 {
     }
   }
 }
+
+namespace PR46859 {
+  extern "bogus" // expected-error {{unknown linkage language}}
+    template<int> struct X {}; // expected-error {{templates can only be declared in namespace or class scope}}
+}