PR15539: Record "evaluating if/elif condition" flag in the right place

The previous implementation missed the case where the elif condition was
evaluated from the context of an #ifdef that was false causing PR15539.

llvm-svn: 177345

clang/lib/Lex/PPDirectives.cpp

@@ -2082,7 +2082,6 @@ void Preprocessor::HandleIfdefDirective(Token &Result, bool isIfndef,
 ///
 void Preprocessor::HandleIfDirective(Token &IfToken,
                                      bool ReadAnyTokensBeforeDirective) {
-  SaveAndRestore<bool> PPDir(ParsingIfOrElifDirective, true);
   ++NumIf;
 
   // Parse and evaluate the conditional expression.
@@ -2174,7 +2173,6 @@ void Preprocessor::HandleElseDirective(Token &Result) {
 /// HandleElifDirective - Implements the \#elif directive.
 ///
 void Preprocessor::HandleElifDirective(Token &ElifToken) {
-  SaveAndRestore<bool> PPDir(ParsingIfOrElifDirective, true);
   ++NumElse;
 
   // #elif directive in a non-skipping conditional... start skipping.

clang/lib/Lex/PPExpressions.cpp

@@ -24,6 +24,7 @@
 #include "clang/Lex/MacroInfo.h"
 #include "llvm/ADT/APSInt.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/SaveAndRestore.h"
 using namespace clang;
 
 namespace {
@@ -730,6 +731,7 @@ static bool EvaluateDirectiveSubExpr(PPValue &LHS, unsigned MinPrec,
 /// to "!defined(X)" return X in IfNDefMacro.
 bool Preprocessor::
 EvaluateDirectiveExpression(IdentifierInfo *&IfNDefMacro) {
+  SaveAndRestore<bool> PPDir(ParsingIfOrElifDirective, true);
   // Save the current state of 'DisableMacroExpansion' and reset it to false. If
   // 'DisableMacroExpansion' is true, then we must be in a macro argument list
   // in which case a directive is undefined behavior.  We want macros to be able

clang/test/Preprocessor/has_include.c

@@ -176,3 +176,12 @@ __has_include
 #else
   #error "__has_include failed (9)."
 #endif
+
+#if FOO
+#elif __has_include(<foo>)
+#endif
+
+// PR15539
+#ifdef FOO
+#elif __has_include(<foo>)
+#endif