Lex: Don't lex after getting EOF when handling _Pragma

[majnemer]

Summary

The error recovery path in _Pragma attempted to lex past the non-string
literal token and then lex past a closing right paren if it exists.

However, this path wasn't careful in the face of EOF.

This fixes PR20662.

[rsmith]

lib/Lex/Pragma.cpp

196

I think you should also stop at EOD and EOM (that is, tok::eod and tok::annot_module_*).

[rnk]

I landed a change like this in r215672, but I don't have mail for it yet... Not sure what's up.

[majnemer]

Superseded by rL215672.

lib/Lex/Pragma.cpp

if (Tok.isNot(tok::l_paren)) {
     return _PragmaLexing.failed();
   }
 
   // Read the '"..."'.
   Lex(Tok);
   if (!tok::isStringLiteral(Tok.getKind())) {
     Diag(PragmaLoc, diag::err__Pragma_malformed);
     // Skip this token, and the ')', if present.
-    if (Tok.isNot(tok::r_paren))
+    if (Tok.isNot(tok::eof) && Tok.isNot(tok::r_paren))
       Lex(Tok);
     if (Tok.is(tok::r_paren))
       Lex(Tok);
     return _PragmaLexing.failed();
   }
 
   if (Tok.hasUDSuffix()) {
     Diag(Tok, diag::err_invalid_string_udl);

test/Preprocessor/_Pragma.c

 // RUN: %clang_cc1 %s -verify -Wall
 
 _Pragma ("GCC system_header")  // expected-warning {{system_header ignored in main file}}
 
 // rdar://6880630
 _Pragma("#define macro")    // expected-warning {{unknown pragma ignored}}
 
 _Pragma("") // expected-warning {{unknown pragma ignored}}
 _Pragma("message(\"foo \\\\\\\\ bar\")") // expected-warning {{foo \\ bar}}
 
 #ifdef macro
 #error #define invalid
 #endif
+
+_Pragma( // expected-error {{_Pragma takes a parenthesized string literal}}