[clang] Bump AS_GNU to 1

[rsandifo-arm]

Summary

Following a suggestion from Erich in https://reviews.llvm.org/D148101,
this patch bumps AS_GNU to 1 so that syntax 0 is invalid. It also
asserts that the syntax is in range.

[erichkeane]

This LGTM, though curious about the re-ordering.

clang/include/clang/Basic/AttributeCommonInfo.h

135

Did these two ctors swap places somehow? There's something goofy going on here? Or is this just to make the delegation of ctors more sensible?

[erichkeane]

clang/include/clang/Basic/AttributeCommonInfo.h

28

Note for others: we're now at 11 items (10 items + starting at 1), stored in 4 bits. So this doesn't cause problems. In the future, once we're sure the '0' case isn't being used/abused for a while (god help my downstream...), we can start re-using 0.

[rsandifo-arm]

clang/include/clang/Basic/AttributeCommonInfo.h

135

Ah, yeah, I should have mentioned that, sorry. The most general constructor was previously the second in the list. Like you say, I moved it up to make the delegation more obvious. The other three keep their relative order.

[erichkeane]

clang/include/clang/Basic/AttributeCommonInfo.h

135

Thanks for explaining, sounds good to me.

[rsandifo-arm]

Gah, sorry. Due to a botched git operation, I posted a first cut with a stupid typo, rather than the version that passed testing.

clang/include/clang/Basic/AttributeCommonInfo.h

 class IdentifierInfo;
 class ASTRecordWriter;
 
 class AttributeCommonInfo {
 public:
   /// The style used to specify an attribute.
   enum Syntax {
     /// __attribute__((...))
-    AS_GNU,
+    AS_GNU = 1,
 
     /// [[...]]
     AS_CXX11,
 
     /// [[...]]
     AS_C2x,
 
     /// __declspec(...)
private:
 
     unsigned SyntaxUsed : 4;
     unsigned SpellingIndex : 4;
     unsigned IsAlignas : 1;
   };
 
   AttributeCommonInfo(const IdentifierInfo *AttrName,
                       const IdentifierInfo *ScopeName, SourceRange AttrRange,
-                      SourceLocation ScopeLoc, Form FormUsed)
+                      SourceLocation ScopeLoc, Kind AttrKind, Form FormUsed)
       : AttrName(AttrName), ScopeName(ScopeName), AttrRange(AttrRange),
-        ScopeLoc(ScopeLoc),
-        AttrKind(getParsedKind(AttrName, ScopeName, FormUsed.getSyntax())),
+        ScopeLoc(ScopeLoc), AttrKind(AttrKind),
         SyntaxUsed(FormUsed.getSyntax()),
         SpellingIndex(FormUsed.getSpellingIndex()),
-        IsAlignas(FormUsed.isAlignas()) {}
+        IsAlignas(FormUsed.isAlignas()) {
+    assert(SyntaxUsed >= AS_GNU && SyntaxUsed <= AS_Implicit &&
+           "Invalid syntax!");
+  }
 
   AttributeCommonInfo(const IdentifierInfo *AttrName,
                       const IdentifierInfo *ScopeName, SourceRange AttrRange,
-                      SourceLocation ScopeLoc, Kind AttrKind, Form FormUsed)
-      : AttrName(AttrName), ScopeName(ScopeName), AttrRange(AttrRange),
-        ScopeLoc(ScopeLoc), AttrKind(AttrKind),
-        SyntaxUsed(FormUsed.getSyntax()),
-        SpellingIndex(FormUsed.getSpellingIndex()),
-        IsAlignas(FormUsed.isAlignas()) {}
+                      SourceLocation ScopeLoc, Form FormUsed)
+      : AttributeCommonInfo(
+            AttrName, ScopeName, AttrRange, ScopeLoc,
+            getParsedKind(AttrName, ScopeName, FormUsed.getSyntax()),
+            FormUsed) {}
 
   AttributeCommonInfo(const IdentifierInfo *AttrName, SourceRange AttrRange,
                       Form FormUsed)
-      : AttrName(AttrName), ScopeName(nullptr), AttrRange(AttrRange),
-        ScopeLoc(),
-        AttrKind(getParsedKind(AttrName, ScopeName, FormUsed.getSyntax())),
-        SyntaxUsed(FormUsed.getSyntax()),
-        SpellingIndex(FormUsed.getSpellingIndex()),
-        IsAlignas(FormUsed.isAlignas()) {}
+      : AttributeCommonInfo(AttrName, nullptr, AttrRange, SourceLocation(),
+                            FormUsed) {}
 
   AttributeCommonInfo(SourceRange AttrRange, Kind K, Form FormUsed)
-      : AttrName(nullptr), ScopeName(nullptr), AttrRange(AttrRange), ScopeLoc(),
-        AttrKind(K), SyntaxUsed(FormUsed.getSyntax()),
-        SpellingIndex(FormUsed.getSpellingIndex()),
-        IsAlignas(FormUsed.isAlignas()) {}
+      : AttributeCommonInfo(nullptr, nullptr, AttrRange, SourceLocation(), K,
+                            FormUsed) {}
 
   AttributeCommonInfo(AttributeCommonInfo &&) = default;
   AttributeCommonInfo(const AttributeCommonInfo &) = default;
 
   Kind getParsedKind() const { return Kind(AttrKind); }
   Syntax getSyntax() const { return Syntax(SyntaxUsed); }
   Form getForm() const { return Form(getSyntax(), SpellingIndex, IsAlignas); }
   const IdentifierInfo *getAttrName() const { return AttrName; }