[MC] - Disallow invalid section groups declarations.

[grimar]

Summary

This fixes parseGroup() so that it always sets error condition on error.
Previously it was not done, because parseIdentifier looks never do that,
assuming that caller should do it if he wants to.

So previously cases from test were silently accepted and produced broken output.

lib/MC/MCParser/ELFAsmParser.cpp

bool ELFAsmParser::parseGroup(StringRef &GroupName) {
   MCAsmLexer &L = getLexer();
   if (L.isNot(AsmToken::Comma))
     return TokError("expected group name");
   Lex();
   if (L.is(AsmToken::Integer)) {
     GroupName = getTok().getString();
     Lex();
   } else if (getParser().parseIdentifier(GroupName)) {
-    return true;
+    return TokError("invalid group name");
   }
   if (L.is(AsmToken::Comma)) {
     Lex();
     StringRef Linkage;
     if (getParser().parseIdentifier(Linkage))
-      return true;
+      return TokError("invalid linkage");
     if (Linkage != "comdat")
       return TokError("Linkage must be 'comdat'");
   }
   return false;
 }
 
 bool ELFAsmParser::parseMetadataSym(MCSymbolELF *&Associated) {
   MCAsmLexer &L = getLexer();

test/MC/ELF/comdat-declaration-errors.s

+// RUN: not llvm-mc -triple x86_64-pc-linux-gnu %s \
+// RUN:   -filetype=obj -o %t.o 2>&1 | FileCheck %s
+
+// Check we error out on incorrect COMDATs declarations
+// and not just silently ingnore them.
+
+// CHECK:      error: invalid group name
+// CHECK-NEXT: .section .foo,"G",@progbits,-abc,comdat
+
+// CHECK:      error: invalid linkage
+// CHECK-NEXT: .section .bar,"G",@progbits,abc,-comdat
+
+.section .foo,"G",@progbits,-abc,comdat
+.section .bar,"G",@progbits,abc,-comdat