Don't warn for empty 'if' body if there is a macro that expands to nothing, e.g:

  if (condition)
    CALL(0); // empty macro but don't warn for empty body.

Fixes rdar://8436021.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@119838 91177308-0d34-0410-b5e6-96231b3b80d8

7 files changed, 36 insertions, 13 deletions

diff --git a/lib/AST/Stmt.cpp b/lib/AST/Stmt.cpp
index acd77beaca..85e640701b 100644
--- a/lib/AST/Stmt.cpp
+++ b/lib/AST/Stmt.cpp
@@ -470,8 +470,10 @@ CXXTryStmt::CXXTryStmt(SourceLocation tryLoc, Stmt *tryBlock,
 }
 
 IfStmt::IfStmt(ASTContext &C, SourceLocation IL, VarDecl *var, Expr *cond, 
-               Stmt *then, SourceLocation EL, Stmt *elsev)
-  : Stmt(IfStmtClass), IfLoc(IL), ElseLoc(EL)
+               Stmt *then, SourceLocation EL, Stmt *elsev,
+               bool macroExpandedInThenStmt)
+  : Stmt(IfStmtClass), IfLoc(IL), ElseLoc(EL),
+    MacroExpandedInThenStmt(macroExpandedInThenStmt)
 {
   setConditionVariable(C, var);
   SubExprs[COND] = reinterpret_cast<Stmt*>(cond);
diff --git a/lib/Lex/PPMacroExpansion.cpp b/lib/Lex/PPMacroExpansion.cpp
index 2428f9af45..6d2c387d52 100644
--- a/lib/Lex/PPMacroExpansion.cpp
+++ b/lib/Lex/PPMacroExpansion.cpp
@@ -176,6 +176,7 @@ bool Preprocessor::isNextPPTokenLParen() {
 /// expanded as a macro, handle it and return the next token as 'Identifier'.
 bool Preprocessor::HandleMacroExpandedIdentifier(Token &Identifier,
                                                  MacroInfo *MI) {
+  MacroExpansionFlag = true;
   if (Callbacks) Callbacks->MacroExpands(Identifier, MI);
 
   // If this is a macro expansion in the "#if !defined(x)" line for the file,
diff --git a/lib/Parse/ParseStmt.cpp b/lib/Parse/ParseStmt.cpp
index 12444e87bb..e3c15680c2 100644
--- a/lib/Parse/ParseStmt.cpp
+++ b/lib/Parse/ParseStmt.cpp
@@ -538,7 +538,8 @@ StmtResult Parser::ParseCompoundStatementBody(bool isStmtExpr) {
 bool Parser::ParseParenExprOrCondition(ExprResult &ExprResult,
                                        Decl *&DeclResult,
                                        SourceLocation Loc,
-                                       bool ConvertToBoolean) {
+                                       bool ConvertToBoolean,
+                                       bool *MacroExpandedAfterRParen) {
   bool ParseError = false;
   
   SourceLocation LParenLoc = ConsumeParen();
@@ -567,7 +568,14 @@ bool Parser::ParseParenExprOrCondition(ExprResult &ExprResult,
   }
 
   // Otherwise the condition is valid or the rparen is present.
+
+  // Catch a macro expansion after ')'. This is used to know that there is a
+  // macro for 'if' body and not warn for empty body if the macro is empty.
+  PPMacroExpansionTrap MacroExpansionTrap(PP);
   MatchRHSPunctuation(tok::r_paren, LParenLoc);
+  if (MacroExpandedAfterRParen)
+    *MacroExpandedAfterRParen = MacroExpansionTrap.hasMacroExpansionOccured();
+
   return false;
 }
 
@@ -610,7 +618,9 @@ StmtResult Parser::ParseIfStatement(AttributeList *Attr) {
   // Parse the condition.
   ExprResult CondExp;
   Decl *CondVar = 0;
-  if (ParseParenExprOrCondition(CondExp, CondVar, IfLoc, true))
+  bool MacroExpandedInThenStmt;
+  if (ParseParenExprOrCondition(CondExp, CondVar, IfLoc, true,
+                                &MacroExpandedInThenStmt))
     return StmtError();
 
   FullExprArg FullCondExp(Actions.MakeFullExpr(CondExp.get()));
@@ -694,7 +704,7 @@ StmtResult Parser::ParseIfStatement(AttributeList *Attr) {
     ElseStmt = Actions.ActOnNullStmt(ElseStmtLoc);
 
   return Actions.ActOnIfStmt(IfLoc, FullCondExp, CondVar, ThenStmt.get(),
-                             ElseLoc, ElseStmt.get());
+                             MacroExpandedInThenStmt, ElseLoc, ElseStmt.get());
 }
 
 /// ParseSwitchStatement
diff --git a/lib/Sema/SemaStmt.cpp b/lib/Sema/SemaStmt.cpp
index a4f1d34aec..c6194edac3 100644
--- a/lib/Sema/SemaStmt.cpp
+++ b/lib/Sema/SemaStmt.cpp
@@ -282,8 +282,8 @@ Sema::ActOnLabelStmt(SourceLocation IdentLoc, IdentifierInfo *II,
 
 StmtResult
 Sema::ActOnIfStmt(SourceLocation IfLoc, FullExprArg CondVal, Decl *CondVar,
-                  Stmt *thenStmt, SourceLocation ElseLoc,
-                  Stmt *elseStmt) {
+                  Stmt *thenStmt, bool MacroExpandedInThenStmt,
+                  SourceLocation ElseLoc, Stmt *elseStmt) {
   ExprResult CondResult(CondVal.release());
 
   VarDecl *ConditionVar = 0;
@@ -304,17 +304,23 @@ Sema::ActOnIfStmt(SourceLocation IfLoc, FullExprArg CondVal, Decl *CondVar,
   // if (condition);
   //   do_stuff();
   //
-  // NOTE: Do not emit this warning if the body is expanded from a macro.
   if (!elseStmt) {
     if (NullStmt* stmt = dyn_cast<NullStmt>(thenStmt))
-      if (!stmt->getLocStart().isMacroID())
+      // But do not warn if the body is a macro that expands to nothing, e.g:
+      //
+      // #define CALL(x)
+      // if (condition)
+      //   CALL(0);
+      //
+      if (!MacroExpandedInThenStmt)
         Diag(stmt->getSemiLoc(), diag::warn_empty_if_body);
   }
 
   DiagnoseUnusedExprResult(elseStmt);
 
   return Owned(new (Context) IfStmt(Context, IfLoc, ConditionVar, ConditionExpr, 
-                                    thenStmt, ElseLoc, elseStmt));
+                                    thenStmt, ElseLoc, elseStmt,
+                                    MacroExpandedInThenStmt));
 }
 
 /// ConvertIntegerToTypeWarnOnOverflow - Convert the specified APInt to have
diff --git a/lib/Sema/TreeTransform.h b/lib/Sema/TreeTransform.h
index 807346c4c5..3ae4e5c5f4 100644
--- a/lib/Sema/TreeTransform.h
+++ b/lib/Sema/TreeTransform.h
@@ -772,9 +772,11 @@ public:
   /// By default, performs semantic analysis to build the new statement.
   /// Subclasses may override this routine to provide different behavior.
   StmtResult RebuildIfStmt(SourceLocation IfLoc, Sema::FullExprArg Cond,
-                                 VarDecl *CondVar, Stmt *Then, 
+                                 VarDecl *CondVar, Stmt *Then,
+                                 bool MacroExpandedInThenStmt,
                                  SourceLocation ElseLoc, Stmt *Else) {
-    return getSema().ActOnIfStmt(IfLoc, Cond, CondVar, Then, ElseLoc, Else);
+    return getSema().ActOnIfStmt(IfLoc, Cond, CondVar, Then,
+                                 MacroExpandedInThenStmt, ElseLoc, Else);
   }
 
   /// \brief Start building a new switch statement.
@@ -3692,7 +3694,7 @@ TreeTransform<Derived>::TransformIfStmt(IfStmt *S) {
     return SemaRef.Owned(S);
 
   return getDerived().RebuildIfStmt(S->getIfLoc(), FullCond, ConditionVar,
-                                    Then.get(),
+                                    Then.get(), S->hasMacroExpandedInThenStmt(),
                                     S->getElseLoc(), Else.get());
 }
 
diff --git a/lib/Serialization/ASTReaderStmt.cpp b/lib/Serialization/ASTReaderStmt.cpp
index 6d578f616e..a7b42cd3fc 100644
--- a/lib/Serialization/ASTReaderStmt.cpp
+++ b/lib/Serialization/ASTReaderStmt.cpp
@@ -256,6 +256,7 @@ void ASTStmtReader::VisitIfStmt(IfStmt *S) {
   S->setElse(Reader.ReadSubStmt());
   S->setIfLoc(ReadSourceLocation(Record, Idx));
   S->setElseLoc(ReadSourceLocation(Record, Idx));
+  S->MacroExpandedInThenStmt = Record[Idx++];
 }
 
 void ASTStmtReader::VisitSwitchStmt(SwitchStmt *S) {
diff --git a/lib/Serialization/ASTWriterStmt.cpp b/lib/Serialization/ASTWriterStmt.cpp
index 495c3d05ff..a59b772da4 100644
--- a/lib/Serialization/ASTWriterStmt.cpp
+++ b/lib/Serialization/ASTWriterStmt.cpp
@@ -228,6 +228,7 @@ void ASTStmtWriter::VisitIfStmt(IfStmt *S) {
   Writer.AddStmt(S->getElse());
   Writer.AddSourceLocation(S->getIfLoc(), Record);
   Writer.AddSourceLocation(S->getElseLoc(), Record);
+  Record.push_back(S->MacroExpandedInThenStmt);
   Code = serialization::STMT_IF;
 }