[PATCH] D133248: [clang] Fix crash upon stray coloncolon token in C2x mode

[Hu Jialun via Phabricator via cfe-commits]

SuibianP created this revision.
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The parser assumes that the lexer never emits coloncolon token for
C code, but this assumption no longer holds in C2x attribute namespaces.
As a result, stray coloncolon tokens out of attributes cause assertion
failures and hangs in release build, which this patch tries to handle.

Crash input minimal example: T n::v


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D133248

Files:
  clang/include/clang/Parse/Parser.h
  clang/lib/Parse/ParseDecl.cpp
  clang/lib/Parse/Parser.cpp
  clang/test/Parser/c2x-attributes.c


Index: clang/test/Parser/c2x-attributes.c
===================================================================
--- clang/test/Parser/c2x-attributes.c
+++ clang/test/Parser/c2x-attributes.c
@@ -141,3 +141,6 @@
 struct [[]] S4 *s; // expected-error {{an attribute list cannot appear here}}
 struct S5 {};
 int c = sizeof(struct [[]] S5); // expected-error {{an attribute list cannot appear here}}
+
+// Ensure that '::' outside of attributes does not crash and is not treated as scope
+double n::v; // expected-error {{expected ';' after top level declarator}}
Index: clang/lib/Parse/Parser.cpp
===================================================================
--- clang/lib/Parse/Parser.cpp
+++ clang/lib/Parse/Parser.cpp
@@ -2060,9 +2060,9 @@
     }
 
     if (!getLangOpts().CPlusPlus) {
-      // If we're in C, we can't have :: tokens at all (the lexer won't return
-      // them).  If the identifier is not a type, then it can't be scope either,
-      // just early exit.
+      // If we're in C, the only place we can have :: tokens is C2x
+      // attribute which is parsed elsewhere. If the identifier is not a type,
+      // then it can't be scope either, just early exit.
       return false;
     }
 
Index: clang/lib/Parse/ParseDecl.cpp
===================================================================
--- clang/lib/Parse/ParseDecl.cpp
+++ clang/lib/Parse/ParseDecl.cpp
@@ -5336,6 +5336,8 @@
     return isDeclarationSpecifier();
 
   case tok::coloncolon:   // ::foo::bar
+    if (!getLangOpts().CPlusPlus)
+      return false;
     if (NextToken().is(tok::kw_new) ||    // ::new
         NextToken().is(tok::kw_delete))   // ::delete
       return false;
Index: clang/include/clang/Parse/Parser.h
===================================================================
--- clang/include/clang/Parse/Parser.h
+++ clang/include/clang/Parse/Parser.h
@@ -860,10 +860,11 @@
   bool TryAnnotateCXXScopeToken(bool EnteringContext = false);
 
   bool MightBeCXXScopeToken() {
-    return Tok.is(tok::identifier) || Tok.is(tok::coloncolon) ||
-           (Tok.is(tok::annot_template_id) &&
-            NextToken().is(tok::coloncolon)) ||
-           Tok.is(tok::kw_decltype) || Tok.is(tok::kw___super);
+    return (getLangOpts().CPlusPlus) &&
+           (Tok.is(tok::identifier) || Tok.is(tok::coloncolon) ||
+            (Tok.is(tok::annot_template_id) &&
+             NextToken().is(tok::coloncolon)) ||
+            Tok.is(tok::kw_decltype) || Tok.is(tok::kw___super));
   }
   bool TryAnnotateOptionalCXXScopeToken(bool EnteringContext = false) {
     return MightBeCXXScopeToken() && TryAnnotateCXXScopeToken(EnteringContext);


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