r350404 - Refactor the way we handle diagnosing unused expression results.

Richard Smith via cfe-commits cfe-commits at lists.llvm.org
Fri Jan 4 17:41:09 PST 2019


On Fri, 4 Jan 2019 at 17:33, Nico Weber via cfe-commits <
cfe-commits at lists.llvm.org> wrote:

> Nice, this is finding bugs:
> https://bugs.chromium.org/p/chromium/issues/detail?id=919262
>
> However, I noticed that for that case, the same warning is printed twice:
>
> ../../third_party/crashpad/crashpad/util/win/process_info.cc(227,36):
> error: expression result unused [-Werror,-Wunused-value]
>       NTSTATUS_LOG(ERROR, status), "NtQueryInformationProcess";
>                                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> ../../third_party/crashpad/crashpad/util/win/process_info.cc(227,36):
> error: expression result unused [-Werror,-Wunused-value]
>       NTSTATUS_LOG(ERROR, status), "NtQueryInformationProcess";
>
>
> Is that expected?
>

The first diagnostic appears when parsing the template, the second one
appears when instantiating it. In the complete diagnostic output:

../../third_party/crashpad/crashpad/util/win/process_info.cc(227,36):
error: expression result unused [-Werror,-Wunused-value]
      NTSTATUS_LOG(ERROR, status), "NtQueryInformationProcess";
                                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~

../../third_party/crashpad/crashpad/util/win/process_info.cc(227,36):
error: expression result unused [-Werror,-Wunused-value]
      NTSTATUS_LOG(ERROR, status), "NtQueryInformationProcess";
                                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~
../../third_party/crashpad/crashpad/util/win/process_info.cc(531,17):
note: in instantiation of function template specialization
'crashpad::GetProcessBasicInformation<crashpad::process_types::internal::Traits32>'
requested here
  bool result =
GetProcessBasicInformation<process_types::internal::Traits32>(
                ^

It'd be nice to suppress the diagnostic during instantiation if it appeared
during the initial parse (generally, not with something specific to this
warning).

Code is here:
>
> https://cs.chromium.org/chromium/src/third_party/crashpad/crashpad/util/win/process_info.cc?q=crashpad/util/win/process_info.cc&sq=package:chromium&g=0&l=227
>
> https://cs.chromium.org/chromium/src/third_party/crashpad/crashpad/util/win/ntstatus_logging.h?type=cs&q=NTSTATUS_LOG&sq=package:chromium&g=0&l=63
>
>
> On Fri, Jan 4, 2019 at 12:01 PM Aaron Ballman via cfe-commits <
> cfe-commits at lists.llvm.org> wrote:
>
>> Author: aaronballman
>> Date: Fri Jan  4 08:58:14 2019
>> New Revision: 350404
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=350404&view=rev
>> Log:
>> Refactor the way we handle diagnosing unused expression results.
>>
>> Rather than sprinkle calls to DiagnoseUnusedExprResult() around in places
>> where we want diagnostics, we now diagnose unused expression statements and
>> full expressions in a more generic way when acting on the final expression
>> statement. This results in more appropriate diagnostics for [[nodiscard]]
>> where we were previously lacking them, such as when the body of a for loop
>> is not a compound statement.
>>
>> This patch fixes PR39837.
>>
>> Modified:
>>     cfe/trunk/include/clang/Parse/Parser.h
>>     cfe/trunk/include/clang/Sema/Sema.h
>>     cfe/trunk/lib/Parse/ParseObjc.cpp
>>     cfe/trunk/lib/Parse/ParseOpenMP.cpp
>>     cfe/trunk/lib/Parse/ParseStmt.cpp
>>     cfe/trunk/lib/Sema/SemaCoroutine.cpp
>>     cfe/trunk/lib/Sema/SemaDecl.cpp
>>     cfe/trunk/lib/Sema/SemaDeclCXX.cpp
>>     cfe/trunk/lib/Sema/SemaExpr.cpp
>>     cfe/trunk/lib/Sema/SemaExprCXX.cpp
>>     cfe/trunk/lib/Sema/SemaLambda.cpp
>>     cfe/trunk/lib/Sema/SemaOpenMP.cpp
>>     cfe/trunk/lib/Sema/SemaStmt.cpp
>>     cfe/trunk/lib/Sema/TreeTransform.h
>>     cfe/trunk/test/CXX/stmt.stmt/stmt.select/p3.cpp
>>     cfe/trunk/test/CodeCompletion/pragma-macro-token-caching.c
>>     cfe/trunk/test/Parser/cxx1z-init-statement.cpp
>>     cfe/trunk/test/Parser/switch-recovery.cpp
>>     cfe/trunk/test/SemaCXX/cxx1z-init-statement.cpp
>>     cfe/trunk/test/SemaCXX/for-range-examples.cpp
>>     cfe/trunk/test/SemaCXX/warn-unused-result.cpp
>>
>> Modified: cfe/trunk/include/clang/Parse/Parser.h
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Parse/Parser.h?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/include/clang/Parse/Parser.h (original)
>> +++ cfe/trunk/include/clang/Parse/Parser.h Fri Jan  4 08:58:14 2019
>> @@ -360,6 +360,11 @@ class Parser : public CodeCompletionHand
>>    /// just a regular sub-expression.
>>    SourceLocation ExprStatementTokLoc;
>>
>> +  /// Tests whether an expression value is discarded based on token
>> lookahead.
>> +  /// It will return true if the lexer is currently processing the })
>> +  /// terminating a GNU statement expression and false otherwise.
>> +  bool isExprValueDiscarded();
>> +
>>  public:
>>    Parser(Preprocessor &PP, Sema &Actions, bool SkipFunctionBodies);
>>    ~Parser() override;
>>
>> Modified: cfe/trunk/include/clang/Sema/Sema.h
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Sema/Sema.h?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/include/clang/Sema/Sema.h (original)
>> +++ cfe/trunk/include/clang/Sema/Sema.h Fri Jan  4 08:58:14 2019
>> @@ -1365,6 +1365,7 @@ public:
>>    void PopCompoundScope();
>>
>>    sema::CompoundScopeInfo &getCurCompoundScope() const;
>> +  bool isCurCompoundStmtAStmtExpr() const;
>>
>>    bool hasAnyUnrecoverableErrorsInThisFunction() const;
>>
>> @@ -3685,16 +3686,17 @@ public:
>>      return MakeFullExpr(Arg, Arg ? Arg->getExprLoc() : SourceLocation());
>>    }
>>    FullExprArg MakeFullExpr(Expr *Arg, SourceLocation CC) {
>> -    return FullExprArg(ActOnFinishFullExpr(Arg, CC).get());
>> +    return FullExprArg(
>> +        ActOnFinishFullExpr(Arg, CC, /*DiscardedValue*/ false).get());
>>    }
>>    FullExprArg MakeFullDiscardedValueExpr(Expr *Arg) {
>>      ExprResult FE =
>> -      ActOnFinishFullExpr(Arg, Arg ? Arg->getExprLoc() :
>> SourceLocation(),
>> -                          /*DiscardedValue*/ true);
>> +        ActOnFinishFullExpr(Arg, Arg ? Arg->getExprLoc() :
>> SourceLocation(),
>> +                            /*DiscardedValue*/ true);
>>      return FullExprArg(FE.get());
>>    }
>>
>> -  StmtResult ActOnExprStmt(ExprResult Arg);
>> +  StmtResult ActOnExprStmt(ExprResult Arg, bool DiscardedValue = true);
>>    StmtResult ActOnExprStmtError();
>>
>>    StmtResult ActOnNullStmt(SourceLocation SemiLoc,
>> @@ -5340,13 +5342,12 @@ public:
>>    CreateMaterializeTemporaryExpr(QualType T, Expr *Temporary,
>>                                   bool BoundToLvalueReference);
>>
>> -  ExprResult ActOnFinishFullExpr(Expr *Expr) {
>> -    return ActOnFinishFullExpr(Expr, Expr ? Expr->getExprLoc()
>> -                                          : SourceLocation());
>> +  ExprResult ActOnFinishFullExpr(Expr *Expr, bool DiscardedValue) {
>> +    return ActOnFinishFullExpr(
>> +        Expr, Expr ? Expr->getExprLoc() : SourceLocation(),
>> DiscardedValue);
>>    }
>>    ExprResult ActOnFinishFullExpr(Expr *Expr, SourceLocation CC,
>> -                                 bool DiscardedValue = false,
>> -                                 bool IsConstexpr = false);
>> +                                 bool DiscardedValue, bool IsConstexpr =
>> false);
>>    StmtResult ActOnFinishFullStmt(Stmt *Stmt);
>>
>>    // Marks SS invalid if it represents an incomplete type.
>>
>> Modified: cfe/trunk/lib/Parse/ParseObjc.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Parse/ParseObjc.cpp?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Parse/ParseObjc.cpp (original)
>> +++ cfe/trunk/lib/Parse/ParseObjc.cpp Fri Jan  4 08:58:14 2019
>> @@ -2741,7 +2741,7 @@ StmtResult Parser::ParseObjCAtStatement(
>>
>>    // Otherwise, eat the semicolon.
>>    ExpectAndConsumeSemi(diag::err_expected_semi_after_expr);
>> -  return Actions.ActOnExprStmt(Res);
>> +  return Actions.ActOnExprStmt(Res, isExprValueDiscarded());
>>  }
>>
>>  ExprResult Parser::ParseObjCAtExpression(SourceLocation AtLoc) {
>>
>> Modified: cfe/trunk/lib/Parse/ParseOpenMP.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Parse/ParseOpenMP.cpp?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Parse/ParseOpenMP.cpp (original)
>> +++ cfe/trunk/lib/Parse/ParseOpenMP.cpp Fri Jan  4 08:58:14 2019
>> @@ -314,7 +314,7 @@ Parser::ParseOpenMPDeclareReductionDirec
>>      Actions.ActOnOpenMPDeclareReductionCombinerStart(getCurScope(), D);
>>      ExprResult CombinerResult =
>>          Actions.ActOnFinishFullExpr(ParseAssignmentExpression().get(),
>> -                                    D->getLocation(),
>> /*DiscardedValue=*/true);
>> +                                    D->getLocation(), /*DiscardedValue*/
>> false);
>>      Actions.ActOnOpenMPDeclareReductionCombinerEnd(D,
>> CombinerResult.get());
>>
>>      if (CombinerResult.isInvalid() && Tok.isNot(tok::r_paren) &&
>> @@ -356,7 +356,7 @@ Parser::ParseOpenMPDeclareReductionDirec
>>            if (Actions.getLangOpts().CPlusPlus) {
>>              InitializerResult = Actions.ActOnFinishFullExpr(
>>                  ParseAssignmentExpression().get(), D->getLocation(),
>> -                /*DiscardedValue=*/true);
>> +                /*DiscardedValue*/ false);
>>            } else {
>>              ConsumeToken();
>>              ParseOpenMPReductionInitializerForDecl(OmpPrivParm);
>> @@ -364,7 +364,7 @@ Parser::ParseOpenMPDeclareReductionDirec
>>          } else {
>>            InitializerResult = Actions.ActOnFinishFullExpr(
>>                ParseAssignmentExpression().get(), D->getLocation(),
>> -              /*DiscardedValue=*/true);
>> +              /*DiscardedValue*/ false);
>>          }
>>          Actions.ActOnOpenMPDeclareReductionInitializerEnd(
>>              D, InitializerResult.get(), OmpPrivParm);
>> @@ -1455,7 +1455,7 @@ ExprResult Parser::ParseOpenMPParensExpr
>>    ExprResult LHS(ParseCastExpression(
>>        /*isUnaryExpression=*/false, /*isAddressOfOperand=*/false,
>> NotTypeCast));
>>    ExprResult Val(ParseRHSOfBinaryExpression(LHS, prec::Conditional));
>> -  Val = Actions.ActOnFinishFullExpr(Val.get(), ELoc);
>> +  Val = Actions.ActOnFinishFullExpr(Val.get(), ELoc, /*DiscardedValue*/
>> false);
>>
>>    // Parse ')'.
>>    RLoc = Tok.getLocation();
>> @@ -1711,7 +1711,8 @@ OMPClause *Parser::ParseOpenMPSingleExpr
>>      SourceLocation ELoc = Tok.getLocation();
>>      ExprResult LHS(ParseCastExpression(false, false, NotTypeCast));
>>      Val = ParseRHSOfBinaryExpression(LHS, prec::Conditional);
>> -    Val = Actions.ActOnFinishFullExpr(Val.get(), ELoc);
>> +    Val =
>> +        Actions.ActOnFinishFullExpr(Val.get(), ELoc, /*DiscardedValue*/
>> false);
>>    }
>>
>>    // Parse ')'.
>> @@ -1996,7 +1997,8 @@ bool Parser::ParseOpenMPVarList(OpenMPDi
>>      Data.ColonLoc = Tok.getLocation();
>>      SourceLocation ELoc = ConsumeToken();
>>      ExprResult Tail = ParseAssignmentExpression();
>> -    Tail = Actions.ActOnFinishFullExpr(Tail.get(), ELoc);
>> +    Tail =
>> +        Actions.ActOnFinishFullExpr(Tail.get(), ELoc, /*DiscardedValue*/
>> false);
>>      if (Tail.isUsable())
>>        Data.TailExpr = Tail.get();
>>      else
>>
>> Modified: cfe/trunk/lib/Parse/ParseStmt.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Parse/ParseStmt.cpp?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Parse/ParseStmt.cpp (original)
>> +++ cfe/trunk/lib/Parse/ParseStmt.cpp Fri Jan  4 08:58:14 2019
>> @@ -439,7 +439,7 @@ StmtResult Parser::ParseExprStatement()
>>
>>    // Otherwise, eat the semicolon.
>>    ExpectAndConsumeSemi(diag::err_expected_semi_after_expr);
>> -  return Actions.ActOnExprStmt(Expr);
>> +  return Actions.ActOnExprStmt(Expr, isExprValueDiscarded());
>>  }
>>
>>  /// ParseSEHTryBlockCommon
>> @@ -958,6 +958,16 @@ bool Parser::ConsumeNullStmt(StmtVector
>>    return true;
>>  }
>>
>> +bool Parser::isExprValueDiscarded() {
>> +  if (Actions.isCurCompoundStmtAStmtExpr()) {
>> +    // Look to see if the next two tokens close the statement expression;
>> +    // if so, this expression statement is the last statement in a
>> +    // statment expression.
>> +    return Tok.isNot(tok::r_brace) || NextToken().isNot(tok::r_paren);
>> +  }
>> +  return true;
>> +}
>> +
>>  /// ParseCompoundStatementBody - Parse a sequence of statements and
>> invoke the
>>  /// ActOnCompoundStmt action.  This expects the '{' to be the current
>> token, and
>>  /// consume the '}' at the end of the block.  It does not manipulate the
>> scope
>> @@ -1062,7 +1072,7 @@ StmtResult Parser::ParseCompoundStatemen
>>          // Eat the semicolon at the end of stmt and convert the expr
>> into a
>>          // statement.
>>          ExpectAndConsumeSemi(diag::err_expected_semi_after_expr);
>> -        R = Actions.ActOnExprStmt(Res);
>> +        R = Actions.ActOnExprStmt(Res, isExprValueDiscarded());
>>        }
>>      }
>>
>> @@ -1698,8 +1708,16 @@ StmtResult Parser::ParseForStatement(Sou
>>      if (!Value.isInvalid()) {
>>        if (ForEach)
>>          FirstPart = Actions.ActOnForEachLValueExpr(Value.get());
>> -      else
>> -        FirstPart = Actions.ActOnExprStmt(Value);
>> +      else {
>> +        // We already know this is not an init-statement within a for
>> loop, so
>> +        // if we are parsing a C++11 range-based for loop, we should
>> treat this
>> +        // expression statement as being a discarded value expression
>> because
>> +        // we will err below. This way we do not warn on an unused
>> expression
>> +        // that was an error in the first place, like with: for (expr :
>> expr);
>> +        bool IsRangeBasedFor =
>> +            getLangOpts().CPlusPlus11 && !ForEach && Tok.is(tok::colon);
>> +        FirstPart = Actions.ActOnExprStmt(Value, !IsRangeBasedFor);
>> +      }
>>      }
>>
>>      if (Tok.is(tok::semi)) {
>>
>> Modified: cfe/trunk/lib/Sema/SemaCoroutine.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaCoroutine.cpp?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Sema/SemaCoroutine.cpp (original)
>> +++ cfe/trunk/lib/Sema/SemaCoroutine.cpp Fri Jan  4 08:58:14 2019
>> @@ -647,7 +647,7 @@ bool Sema::ActOnCoroutineBodyStart(Scope
>>        return StmtError();
>>      Suspend = BuildResolvedCoawaitExpr(Loc, Suspend.get(),
>>                                         /*IsImplicit*/ true);
>> -    Suspend = ActOnFinishFullExpr(Suspend.get());
>> +    Suspend = ActOnFinishFullExpr(Suspend.get(), /*DiscardedValue*/
>> false);
>>      if (Suspend.isInvalid()) {
>>        Diag(Loc, diag::note_coroutine_promise_suspend_implicitly_required)
>>            << ((Name == "initial_suspend") ? 0 : 1);
>> @@ -868,7 +868,7 @@ StmtResult Sema::BuildCoreturnStmt(Sourc
>>    if (PC.isInvalid())
>>      return StmtError();
>>
>> -  Expr *PCE = ActOnFinishFullExpr(PC.get()).get();
>> +  Expr *PCE = ActOnFinishFullExpr(PC.get(), /*DiscardedValue*/
>> false).get();
>>
>>    Stmt *Res = new (Context) CoreturnStmt(Loc, E, PCE, IsImplicit);
>>    return Res;
>> @@ -1237,7 +1237,7 @@ bool CoroutineStmtBuilder::makeNewAndDel
>>
>>    ExprResult NewExpr =
>>        S.ActOnCallExpr(S.getCurScope(), NewRef.get(), Loc, NewArgs, Loc);
>> -  NewExpr = S.ActOnFinishFullExpr(NewExpr.get());
>> +  NewExpr = S.ActOnFinishFullExpr(NewExpr.get(), /*DiscardedValue*/
>> false);
>>    if (NewExpr.isInvalid())
>>      return false;
>>
>> @@ -1263,7 +1263,8 @@ bool CoroutineStmtBuilder::makeNewAndDel
>>
>>    ExprResult DeleteExpr =
>>        S.ActOnCallExpr(S.getCurScope(), DeleteRef.get(), Loc, DeleteArgs,
>> Loc);
>> -  DeleteExpr = S.ActOnFinishFullExpr(DeleteExpr.get());
>> +  DeleteExpr =
>> +      S.ActOnFinishFullExpr(DeleteExpr.get(), /*DiscardedValue*/ false);
>>    if (DeleteExpr.isInvalid())
>>      return false;
>>
>> @@ -1348,7 +1349,8 @@ bool CoroutineStmtBuilder::makeOnExcepti
>>
>>    ExprResult UnhandledException = buildPromiseCall(S,
>> Fn.CoroutinePromise, Loc,
>>
>> "unhandled_exception", None);
>> -  UnhandledException = S.ActOnFinishFullExpr(UnhandledException.get(),
>> Loc);
>> +  UnhandledException = S.ActOnFinishFullExpr(UnhandledException.get(),
>> Loc,
>> +                                             /*DiscardedValue*/ false);
>>    if (UnhandledException.isInvalid())
>>      return false;
>>
>> @@ -1401,7 +1403,8 @@ bool CoroutineStmtBuilder::makeGroDeclAn
>>           "get_return_object type must no longer be dependent");
>>
>>    if (FnRetType->isVoidType()) {
>> -    ExprResult Res = S.ActOnFinishFullExpr(this->ReturnValue, Loc);
>> +    ExprResult Res =
>> +        S.ActOnFinishFullExpr(this->ReturnValue, Loc, /*DiscardedValue*/
>> false);
>>      if (Res.isInvalid())
>>        return false;
>>
>> @@ -1433,7 +1436,7 @@ bool CoroutineStmtBuilder::makeGroDeclAn
>>    if (Res.isInvalid())
>>      return false;
>>
>> -  Res = S.ActOnFinishFullExpr(Res.get());
>> +  Res = S.ActOnFinishFullExpr(Res.get(), /*DiscardedValue*/ false);
>>    if (Res.isInvalid())
>>      return false;
>>
>>
>> Modified: cfe/trunk/lib/Sema/SemaDecl.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDecl.cpp?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Sema/SemaDecl.cpp (original)
>> +++ cfe/trunk/lib/Sema/SemaDecl.cpp Fri Jan  4 08:58:14 2019
>> @@ -11204,9 +11204,9 @@ void Sema::AddInitializerToDecl(Decl *Re
>>    //   struct T { S a, b; } t = { Temp(), Temp() }
>>    //
>>    // we should destroy the first Temp before constructing the second.
>> -  ExprResult Result = ActOnFinishFullExpr(Init, VDecl->getLocation(),
>> -                                          false,
>> -                                          VDecl->isConstexpr());
>> +  ExprResult Result =
>> +      ActOnFinishFullExpr(Init, VDecl->getLocation(),
>> +                          /*DiscardedValue*/ false,
>> VDecl->isConstexpr());
>>    if (Result.isInvalid()) {
>>      VDecl->setInvalidDecl();
>>      return;
>>
>> Modified: cfe/trunk/lib/Sema/SemaDeclCXX.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDeclCXX.cpp?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Sema/SemaDeclCXX.cpp (original)
>> +++ cfe/trunk/lib/Sema/SemaDeclCXX.cpp Fri Jan  4 08:58:14 2019
>> @@ -1205,7 +1205,7 @@ static bool checkTupleLikeDecomposition(
>>      E = Seq.Perform(S, Entity, Kind, Init);
>>      if (E.isInvalid())
>>        return true;
>> -    E = S.ActOnFinishFullExpr(E.get(), Loc);
>> +    E = S.ActOnFinishFullExpr(E.get(), Loc, /*DiscardedValue*/ false);
>>      if (E.isInvalid())
>>        return true;
>>      RefVD->setInit(E.get());
>> @@ -3682,7 +3682,7 @@ void Sema::ActOnFinishCXXInClassMemberIn
>>    // C++11 [class.base.init]p7:
>>    //   The initialization of each base and member constitutes a
>>    //   full-expression.
>> -  Init = ActOnFinishFullExpr(Init.get(), InitLoc);
>> +  Init = ActOnFinishFullExpr(Init.get(), InitLoc, /*DiscardedValue*/
>> false);
>>    if (Init.isInvalid()) {
>>      FD->setInvalidDecl();
>>      return;
>> @@ -4040,7 +4040,8 @@ Sema::BuildMemberInitializer(ValueDecl *
>>      // C++11 [class.base.init]p7:
>>      //   The initialization of each base and member constitutes a
>>      //   full-expression.
>> -    MemberInit = ActOnFinishFullExpr(MemberInit.get(),
>> InitRange.getBegin());
>> +    MemberInit = ActOnFinishFullExpr(MemberInit.get(),
>> InitRange.getBegin(),
>> +                                     /*DiscardedValue*/ false);
>>      if (MemberInit.isInvalid())
>>        return true;
>>
>> @@ -4095,8 +4096,8 @@ Sema::BuildDelegatingInitializer(TypeSou
>>    // C++11 [class.base.init]p7:
>>    //   The initialization of each base and member constitutes a
>>    //   full-expression.
>> -  DelegationInit = ActOnFinishFullExpr(DelegationInit.get(),
>> -                                       InitRange.getBegin());
>> +  DelegationInit = ActOnFinishFullExpr(
>> +      DelegationInit.get(), InitRange.getBegin(), /*DiscardedValue*/
>> false);
>>    if (DelegationInit.isInvalid())
>>      return true;
>>
>> @@ -4225,7 +4226,8 @@ Sema::BuildBaseInitializer(QualType Base
>>    // C++11 [class.base.init]p7:
>>    //   The initialization of each base and member constitutes a
>>    //   full-expression.
>> -  BaseInit = ActOnFinishFullExpr(BaseInit.get(), InitRange.getBegin());
>> +  BaseInit = ActOnFinishFullExpr(BaseInit.get(), InitRange.getBegin(),
>> +                                 /*DiscardedValue*/ false);
>>    if (BaseInit.isInvalid())
>>      return true;
>>
>>
>> Modified: cfe/trunk/lib/Sema/SemaExpr.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
>> +++ cfe/trunk/lib/Sema/SemaExpr.cpp Fri Jan  4 08:58:14 2019
>> @@ -4736,8 +4736,9 @@ bool Sema::CheckCXXDefaultArgExpr(Source
>>      if (Result.isInvalid())
>>        return true;
>>
>> -    Result = ActOnFinishFullExpr(Result.getAs<Expr>(),
>> -                                 Param->getOuterLocStart());
>> +    Result =
>> +        ActOnFinishFullExpr(Result.getAs<Expr>(),
>> Param->getOuterLocStart(),
>> +                            /*DiscardedValue*/ false);
>>      if (Result.isInvalid())
>>        return true;
>>
>>
>> Modified: cfe/trunk/lib/Sema/SemaExprCXX.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExprCXX.cpp?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Sema/SemaExprCXX.cpp (original)
>> +++ cfe/trunk/lib/Sema/SemaExprCXX.cpp Fri Jan  4 08:58:14 2019
>> @@ -7803,6 +7803,8 @@ ExprResult Sema::ActOnFinishFullExpr(Exp
>>      FullExpr = IgnoredValueConversions(FullExpr.get());
>>      if (FullExpr.isInvalid())
>>        return ExprError();
>> +
>> +    DiagnoseUnusedExprResult(FullExpr.get());
>>    }
>>
>>    FullExpr = CorrectDelayedTyposInExpr(FullExpr.get());
>>
>> Modified: cfe/trunk/lib/Sema/SemaLambda.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaLambda.cpp?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Sema/SemaLambda.cpp (original)
>> +++ cfe/trunk/lib/Sema/SemaLambda.cpp Fri Jan  4 08:58:14 2019
>> @@ -1724,7 +1724,7 @@ ExprResult Sema::BuildBlockForLambdaConv
>>                                                   /*NRVO=*/false),
>>        CurrentLocation, Src);
>>    if (!Init.isInvalid())
>> -    Init = ActOnFinishFullExpr(Init.get());
>> +    Init = ActOnFinishFullExpr(Init.get(), /*DiscardedValue*/ false);
>>
>>    if (Init.isInvalid())
>>      return ExprError();
>>
>> Modified: cfe/trunk/lib/Sema/SemaOpenMP.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaOpenMP.cpp?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Sema/SemaOpenMP.cpp (original)
>> +++ cfe/trunk/lib/Sema/SemaOpenMP.cpp Fri Jan  4 08:58:14 2019
>> @@ -5320,7 +5320,7 @@ checkOpenMPLoop(OpenMPDirectiveKind DKin
>>          LastIteration.get(), UB.get());
>>      EUB = SemaRef.BuildBinOp(CurScope, InitLoc, BO_Assign, UB.get(),
>>                               CondOp.get());
>> -    EUB = SemaRef.ActOnFinishFullExpr(EUB.get());
>> +    EUB = SemaRef.ActOnFinishFullExpr(EUB.get(), /*DiscardedValue*/
>> false);
>>
>>      // If we have a combined directive that combines 'distribute', 'for'
>> or
>>      // 'simd' we need to be able to access the bounds of the schedule of
>> the
>> @@ -5349,7 +5349,8 @@ checkOpenMPLoop(OpenMPDirectiveKind DKin
>>                                       LastIteration.get(), CombUB.get());
>>        CombEUB = SemaRef.BuildBinOp(CurScope, InitLoc, BO_Assign,
>> CombUB.get(),
>>                                     CombCondOp.get());
>> -      CombEUB = SemaRef.ActOnFinishFullExpr(CombEUB.get());
>> +      CombEUB =
>> +          SemaRef.ActOnFinishFullExpr(CombEUB.get(), /*DiscardedValue*/
>> false);
>>
>>        const CapturedDecl *CD =
>> cast<CapturedStmt>(AStmt)->getCapturedDecl();
>>        // We expect to have at least 2 more parameters than the 'parallel'
>> @@ -5383,7 +5384,7 @@ checkOpenMPLoop(OpenMPDirectiveKind DKin
>>              ? LB.get()
>>              : SemaRef.ActOnIntegerConstant(SourceLocation(), 0).get();
>>      Init = SemaRef.BuildBinOp(CurScope, InitLoc, BO_Assign, IV.get(),
>> RHS);
>> -    Init = SemaRef.ActOnFinishFullExpr(Init.get());
>> +    Init = SemaRef.ActOnFinishFullExpr(Init.get(), /*DiscardedValue*/
>> false);
>>
>>      if (isOpenMPLoopBoundSharingDirective(DKind)) {
>>        Expr *CombRHS =
>> @@ -5394,7 +5395,8 @@ checkOpenMPLoop(OpenMPDirectiveKind DKin
>>                : SemaRef.ActOnIntegerConstant(SourceLocation(), 0).get();
>>        CombInit =
>>            SemaRef.BuildBinOp(CurScope, InitLoc, BO_Assign, IV.get(),
>> CombRHS);
>> -      CombInit = SemaRef.ActOnFinishFullExpr(CombInit.get());
>> +      CombInit =
>> +          SemaRef.ActOnFinishFullExpr(CombInit.get(), /*DiscardedValue*/
>> false);
>>      }
>>    }
>>
>> @@ -5426,7 +5428,7 @@ checkOpenMPLoop(OpenMPDirectiveKind DKin
>>    if (!Inc.isUsable())
>>      return 0;
>>    Inc = SemaRef.BuildBinOp(CurScope, IncLoc, BO_Assign, IV.get(),
>> Inc.get());
>> -  Inc = SemaRef.ActOnFinishFullExpr(Inc.get());
>> +  Inc = SemaRef.ActOnFinishFullExpr(Inc.get(), /*DiscardedValue*/ false);
>>    if (!Inc.isUsable())
>>      return 0;
>>
>> @@ -5444,7 +5446,8 @@ checkOpenMPLoop(OpenMPDirectiveKind DKin
>>      // LB = LB + ST
>>      NextLB =
>>          SemaRef.BuildBinOp(CurScope, IncLoc, BO_Assign, LB.get(),
>> NextLB.get());
>> -    NextLB = SemaRef.ActOnFinishFullExpr(NextLB.get());
>> +    NextLB =
>> +        SemaRef.ActOnFinishFullExpr(NextLB.get(), /*DiscardedValue*/
>> false);
>>      if (!NextLB.isUsable())
>>        return 0;
>>      // UB + ST
>> @@ -5454,7 +5457,8 @@ checkOpenMPLoop(OpenMPDirectiveKind DKin
>>      // UB = UB + ST
>>      NextUB =
>>          SemaRef.BuildBinOp(CurScope, IncLoc, BO_Assign, UB.get(),
>> NextUB.get());
>> -    NextUB = SemaRef.ActOnFinishFullExpr(NextUB.get());
>> +    NextUB =
>> +        SemaRef.ActOnFinishFullExpr(NextUB.get(), /*DiscardedValue*/
>> false);
>>      if (!NextUB.isUsable())
>>        return 0;
>>      if (isOpenMPLoopBoundSharingDirective(DKind)) {
>> @@ -5465,7 +5469,8 @@ checkOpenMPLoop(OpenMPDirectiveKind DKin
>>        // LB = LB + ST
>>        CombNextLB = SemaRef.BuildBinOp(CurScope, IncLoc, BO_Assign,
>> CombLB.get(),
>>                                        CombNextLB.get());
>> -      CombNextLB = SemaRef.ActOnFinishFullExpr(CombNextLB.get());
>> +      CombNextLB = SemaRef.ActOnFinishFullExpr(CombNextLB.get(),
>> +                                               /*DiscardedValue*/ false);
>>        if (!CombNextLB.isUsable())
>>          return 0;
>>        // UB + ST
>> @@ -5476,7 +5481,8 @@ checkOpenMPLoop(OpenMPDirectiveKind DKin
>>        // UB = UB + ST
>>        CombNextUB = SemaRef.BuildBinOp(CurScope, IncLoc, BO_Assign,
>> CombUB.get(),
>>                                        CombNextUB.get());
>> -      CombNextUB = SemaRef.ActOnFinishFullExpr(CombNextUB.get());
>> +      CombNextUB = SemaRef.ActOnFinishFullExpr(CombNextUB.get(),
>> +                                               /*DiscardedValue*/ false);
>>        if (!CombNextUB.isUsable())
>>          return 0;
>>      }
>> @@ -5497,7 +5503,8 @@ checkOpenMPLoop(OpenMPDirectiveKind DKin
>>      assert(DistInc.isUsable() && "distribute inc expr was not built");
>>      DistInc = SemaRef.BuildBinOp(CurScope, DistIncLoc, BO_Assign,
>> IV.get(),
>>                                   DistInc.get());
>> -    DistInc = SemaRef.ActOnFinishFullExpr(DistInc.get());
>> +    DistInc =
>> +        SemaRef.ActOnFinishFullExpr(DistInc.get(), /*DiscardedValue*/
>> false);
>>      assert(DistInc.isUsable() && "distribute inc expr was not built");
>>
>>      // Build expression: UB = min(UB, prevUB) for #for in composite or
>> combined
>> @@ -5509,7 +5516,8 @@ checkOpenMPLoop(OpenMPDirectiveKind DKin
>>          DistEUBLoc, DistEUBLoc, IsUBGreater.get(), PrevUB.get(),
>> UB.get());
>>      PrevEUB = SemaRef.BuildBinOp(CurScope, DistIncLoc, BO_Assign,
>> UB.get(),
>>                                   CondOp.get());
>> -    PrevEUB = SemaRef.ActOnFinishFullExpr(PrevEUB.get());
>> +    PrevEUB =
>> +        SemaRef.ActOnFinishFullExpr(PrevEUB.get(), /*DiscardedValue*/
>> false);
>>
>>      // Build IV <= PrevUB to be used in parallel for is in combination
>> with
>>      // a distribute directive with schedule(static, 1)
>> @@ -5613,8 +5621,10 @@ checkOpenMPLoop(OpenMPDirectiveKind DKin
>>    Built.IterationVarRef = IV.get();
>>    Built.LastIteration = LastIteration.get();
>>    Built.NumIterations = NumIterations.get();
>> -  Built.CalcLastIteration =
>> -      SemaRef.ActOnFinishFullExpr(CalcLastIteration.get()).get();
>> +  Built.CalcLastIteration = SemaRef
>> +
>> .ActOnFinishFullExpr(CalcLastIteration.get(),
>> +                                                     /*DiscardedValue*/
>> false)
>> +                                .get();
>>    Built.PreCond = PreCond.get();
>>    Built.PreInits = buildPreInits(C, Captures);
>>    Built.Cond = Cond.get();
>> @@ -10267,8 +10277,8 @@ OMPClause *Sema::ActOnOpenMPLastprivateC
>>                                           PseudoDstExpr, PseudoSrcExpr);
>>      if (AssignmentOp.isInvalid())
>>        continue;
>> -    AssignmentOp = ActOnFinishFullExpr(AssignmentOp.get(), ELoc,
>> -                                       /*DiscardedValue=*/true);
>> +    AssignmentOp =
>> +        ActOnFinishFullExpr(AssignmentOp.get(), ELoc, /*DiscardedValue*/
>> false);
>>      if (AssignmentOp.isInvalid())
>>        continue;
>>
>> @@ -11274,7 +11284,8 @@ static bool actOnOMPReductionKindClause(
>>                             BO_Assign, LHSDRE, ConditionalOp);
>>          }
>>          if (ReductionOp.isUsable())
>> -          ReductionOp = S.ActOnFinishFullExpr(ReductionOp.get());
>> +          ReductionOp = S.ActOnFinishFullExpr(ReductionOp.get(),
>> +                                              /*DiscardedValue*/ false);
>>        }
>>        if (!ReductionOp.isUsable())
>>          continue;
>> @@ -11612,7 +11623,7 @@ OMPClause *Sema::ActOnOpenMPLinearClause
>>          buildDeclRefExpr(*this, SaveVar, StepExpr->getType(), StepLoc);
>>      ExprResult CalcStep =
>>          BuildBinOp(CurScope, StepLoc, BO_Assign, SaveRef.get(),
>> StepExpr);
>> -    CalcStep = ActOnFinishFullExpr(CalcStep.get());
>> +    CalcStep = ActOnFinishFullExpr(CalcStep.get(), /*DiscardedValue*/
>> false);
>>
>>      // Warn about zero linear step (it would be probably better
>> specified as
>>      // making corresponding variables 'const').
>> @@ -11700,7 +11711,7 @@ static bool FinishOpenMPLinearClause(OMP
>>      else
>>        Update = *CurPrivate;
>>      Update = SemaRef.ActOnFinishFullExpr(Update.get(), DE->getBeginLoc(),
>> -                                         /*DiscardedValue=*/true);
>> +                                         /*DiscardedValue*/ false);
>>
>>      // Build final: Var = InitExpr + NumIterations * Step
>>      ExprResult Final;
>> @@ -11711,7 +11722,7 @@ static bool FinishOpenMPLinearClause(OMP
>>      else
>>        Final = *CurPrivate;
>>      Final = SemaRef.ActOnFinishFullExpr(Final.get(), DE->getBeginLoc(),
>> -                                        /*DiscardedValue=*/true);
>> +                                        /*DiscardedValue*/ false);
>>
>>      if (!Update.isUsable() || !Final.isUsable()) {
>>        Updates.push_back(nullptr);
>> @@ -11879,7 +11890,7 @@ OMPClause *Sema::ActOnOpenMPCopyinClause
>>      if (AssignmentOp.isInvalid())
>>        continue;
>>      AssignmentOp = ActOnFinishFullExpr(AssignmentOp.get(),
>> DE->getExprLoc(),
>> -                                       /*DiscardedValue=*/true);
>> +                                       /*DiscardedValue*/ false);
>>      if (AssignmentOp.isInvalid())
>>        continue;
>>
>> @@ -11987,8 +11998,8 @@ OMPClause *Sema::ActOnOpenMPCopyprivateC
>>          DSAStack->getCurScope(), ELoc, BO_Assign, PseudoDstExpr,
>> PseudoSrcExpr);
>>      if (AssignmentOp.isInvalid())
>>        continue;
>> -    AssignmentOp = ActOnFinishFullExpr(AssignmentOp.get(), ELoc,
>> -                                       /*DiscardedValue=*/true);
>> +    AssignmentOp =
>> +        ActOnFinishFullExpr(AssignmentOp.get(), ELoc, /*DiscardedValue*/
>> false);
>>      if (AssignmentOp.isInvalid())
>>        continue;
>>
>>
>> Modified: cfe/trunk/lib/Sema/SemaStmt.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaStmt.cpp?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Sema/SemaStmt.cpp (original)
>> +++ cfe/trunk/lib/Sema/SemaStmt.cpp Fri Jan  4 08:58:14 2019
>> @@ -42,12 +42,11 @@
>>  using namespace clang;
>>  using namespace sema;
>>
>> -StmtResult Sema::ActOnExprStmt(ExprResult FE) {
>> +StmtResult Sema::ActOnExprStmt(ExprResult FE, bool DiscardedValue) {
>>    if (FE.isInvalid())
>>      return StmtError();
>>
>> -  FE = ActOnFinishFullExpr(FE.get(), FE.get()->getExprLoc(),
>> -                           /*DiscardedValue*/ true);
>> +  FE = ActOnFinishFullExpr(FE.get(), FE.get()->getExprLoc(),
>> DiscardedValue);
>>    if (FE.isInvalid())
>>      return StmtError();
>>
>> @@ -348,6 +347,10 @@ sema::CompoundScopeInfo &Sema::getCurCom
>>    return getCurFunction()->CompoundScopes.back();
>>  }
>>
>> +bool Sema::isCurCompoundStmtAStmtExpr() const {
>> +  return getCurCompoundScope().IsStmtExpr;
>> +}
>> +
>>  StmtResult Sema::ActOnCompoundStmt(SourceLocation L, SourceLocation R,
>>                                     ArrayRef<Stmt *> Elts, bool
>> isStmtExpr) {
>>    const unsigned NumElts = Elts.size();
>> @@ -370,14 +373,6 @@ StmtResult Sema::ActOnCompoundStmt(Sourc
>>        Diag(D->getLocation(), diag::ext_mixed_decls_code);
>>      }
>>    }
>> -  // Warn about unused expressions in statements.
>> -  for (unsigned i = 0; i != NumElts; ++i) {
>> -    // Ignore statements that are last in a statement expression.
>> -    if (isStmtExpr && i == NumElts - 1)
>> -      continue;
>> -
>> -    DiagnoseUnusedExprResult(Elts[i]);
>> -  }
>>
>>    // Check for suspicious empty body (null statement) in `for' and
>> `while'
>>    // statements.  Don't do anything for template instantiations, this
>> just adds
>> @@ -469,15 +464,12 @@ Sema::ActOnCaseStmt(SourceLocation CaseL
>>
>>  /// ActOnCaseStmtBody - This installs a statement as the body of a case.
>>  void Sema::ActOnCaseStmtBody(Stmt *S, Stmt *SubStmt) {
>> -  DiagnoseUnusedExprResult(SubStmt);
>>    cast<CaseStmt>(S)->setSubStmt(SubStmt);
>>  }
>>
>>  StmtResult
>>  Sema::ActOnDefaultStmt(SourceLocation DefaultLoc, SourceLocation
>> ColonLoc,
>>                         Stmt *SubStmt, Scope *CurScope) {
>> -  DiagnoseUnusedExprResult(SubStmt);
>> -
>>    if (getCurFunction()->SwitchStack.empty()) {
>>      Diag(DefaultLoc, diag::err_default_not_in_switch);
>>      return SubStmt;
>> @@ -571,9 +563,6 @@ StmtResult Sema::BuildIfStmt(SourceLocat
>>    if (IsConstexpr || isa<ObjCAvailabilityCheckExpr>(Cond.get().second))
>>      setFunctionHasBranchProtectedScope();
>>
>> -  DiagnoseUnusedExprResult(thenStmt);
>> -  DiagnoseUnusedExprResult(elseStmt);
>> -
>>    return IfStmt::Create(Context, IfLoc, IsConstexpr, InitStmt,
>> Cond.get().first,
>>                          Cond.get().second, thenStmt, ElseLoc, elseStmt);
>>  }
>> @@ -1301,8 +1290,6 @@ StmtResult Sema::ActOnWhileStmt(SourceLo
>>        !Diags.isIgnored(diag::warn_comma_operator,
>> CondVal.second->getExprLoc()))
>>      CommaVisitor(*this).Visit(CondVal.second);
>>
>> -  DiagnoseUnusedExprResult(Body);
>> -
>>    if (isa<NullStmt>(Body))
>>      getCurCompoundScope().setHasEmptyLoopBodies();
>>
>> @@ -1322,7 +1309,7 @@ Sema::ActOnDoStmt(SourceLocation DoLoc,
>>      return StmtError();
>>    Cond = CondResult.get();
>>
>> -  CondResult = ActOnFinishFullExpr(Cond, DoLoc);
>> +  CondResult = ActOnFinishFullExpr(Cond, DoLoc, /*DiscardedValue*/
>> false);
>>    if (CondResult.isInvalid())
>>      return StmtError();
>>    Cond = CondResult.get();
>> @@ -1332,8 +1319,6 @@ Sema::ActOnDoStmt(SourceLocation DoLoc,
>>        !Diags.isIgnored(diag::warn_comma_operator, Cond->getExprLoc()))
>>      CommaVisitor(*this).Visit(Cond);
>>
>> -  DiagnoseUnusedExprResult(Body);
>> -
>>    return new (Context) DoStmt(Body, Cond, DoLoc, WhileLoc, CondRParen);
>>  }
>>
>> @@ -1778,11 +1763,6 @@ StmtResult Sema::ActOnForStmt(SourceLoca
>>      CommaVisitor(*this).Visit(Second.get().second);
>>
>>    Expr *Third  = third.release().getAs<Expr>();
>> -
>> -  DiagnoseUnusedExprResult(First);
>> -  DiagnoseUnusedExprResult(Third);
>> -  DiagnoseUnusedExprResult(Body);
>> -
>>    if (isa<NullStmt>(Body))
>>      getCurCompoundScope().setHasEmptyLoopBodies();
>>
>> @@ -1802,7 +1782,7 @@ StmtResult Sema::ActOnForEachLValueExpr(
>>    if (result.isInvalid()) return StmtError();
>>    E = result.get();
>>
>> -  ExprResult FullExpr = ActOnFinishFullExpr(E);
>> +  ExprResult FullExpr = ActOnFinishFullExpr(E, /*DiscardedValue*/ false);
>>    if (FullExpr.isInvalid())
>>      return StmtError();
>>    return StmtResult(static_cast<Stmt*>(FullExpr.get()));
>> @@ -1956,7 +1936,8 @@ Sema::ActOnObjCForCollectionStmt(SourceL
>>    if (CollectionExprResult.isInvalid())
>>      return StmtError();
>>
>> -  CollectionExprResult = ActOnFinishFullExpr(CollectionExprResult.get());
>> +  CollectionExprResult =
>> +      ActOnFinishFullExpr(CollectionExprResult.get(), /*DiscardedValue*/
>> false);
>>    if (CollectionExprResult.isInvalid())
>>      return StmtError();
>>
>> @@ -2593,7 +2574,8 @@ StmtResult Sema::BuildCXXForRangeStmt(So
>>      if (!NotEqExpr.isInvalid())
>>        NotEqExpr = CheckBooleanCondition(ColonLoc, NotEqExpr.get());
>>      if (!NotEqExpr.isInvalid())
>> -      NotEqExpr = ActOnFinishFullExpr(NotEqExpr.get());
>> +      NotEqExpr =
>> +          ActOnFinishFullExpr(NotEqExpr.get(), /*DiscardedValue*/ false);
>>      if (NotEqExpr.isInvalid()) {
>>        Diag(RangeLoc, diag::note_for_range_invalid_iterator)
>>          << RangeLoc << 0 << BeginRangeRef.get()->getType();
>> @@ -2616,7 +2598,7 @@ StmtResult Sema::BuildCXXForRangeStmt(So
>>        // co_await during the initial parse.
>>        IncrExpr = ActOnCoawaitExpr(S, CoawaitLoc, IncrExpr.get());
>>      if (!IncrExpr.isInvalid())
>> -      IncrExpr = ActOnFinishFullExpr(IncrExpr.get());
>> +      IncrExpr = ActOnFinishFullExpr(IncrExpr.get(), /*DiscardedValue*/
>> false);
>>      if (IncrExpr.isInvalid()) {
>>        Diag(RangeLoc, diag::note_for_range_invalid_iterator)
>>          << RangeLoc << 2 << BeginRangeRef.get()->getType() ;
>> @@ -2871,7 +2853,7 @@ Sema::ActOnIndirectGotoStmt(SourceLocati
>>        return StmtError();
>>    }
>>
>> -  ExprResult ExprRes = ActOnFinishFullExpr(E);
>> +  ExprResult ExprRes = ActOnFinishFullExpr(E, /*DiscardedValue*/ false);
>>    if (ExprRes.isInvalid())
>>      return StmtError();
>>    E = ExprRes.get();
>> @@ -3221,7 +3203,8 @@ Sema::ActOnCapScopeReturnStmt(SourceLoca
>>            ExpressionEvaluationContext::DiscardedStatement &&
>>        (HasDeducedReturnType || CurCap->HasImplicitReturnType)) {
>>      if (RetValExp) {
>> -      ExprResult ER = ActOnFinishFullExpr(RetValExp, ReturnLoc);
>> +      ExprResult ER =
>> +          ActOnFinishFullExpr(RetValExp, ReturnLoc, /*DiscardedValue*/
>> false);
>>        if (ER.isInvalid())
>>          return StmtError();
>>        RetValExp = ER.get();
>> @@ -3348,7 +3331,8 @@ Sema::ActOnCapScopeReturnStmt(SourceLoca
>>    }
>>
>>    if (RetValExp) {
>> -    ExprResult ER = ActOnFinishFullExpr(RetValExp, ReturnLoc);
>> +    ExprResult ER =
>> +        ActOnFinishFullExpr(RetValExp, ReturnLoc, /*DiscardedValue*/
>> false);
>>      if (ER.isInvalid())
>>        return StmtError();
>>      RetValExp = ER.get();
>> @@ -3578,7 +3562,8 @@ StmtResult Sema::BuildReturnStmt(SourceL
>>            ExpressionEvaluationContext::DiscardedStatement &&
>>        FnRetType->getContainedAutoType()) {
>>      if (RetValExp) {
>> -      ExprResult ER = ActOnFinishFullExpr(RetValExp, ReturnLoc);
>> +      ExprResult ER =
>> +          ActOnFinishFullExpr(RetValExp, ReturnLoc, /*DiscardedValue*/
>> false);
>>        if (ER.isInvalid())
>>          return StmtError();
>>        RetValExp = ER.get();
>> @@ -3672,7 +3657,8 @@ StmtResult Sema::BuildReturnStmt(SourceL
>>        }
>>
>>        if (RetValExp) {
>> -        ExprResult ER = ActOnFinishFullExpr(RetValExp, ReturnLoc);
>> +        ExprResult ER =
>> +            ActOnFinishFullExpr(RetValExp, ReturnLoc, /*DiscardedValue*/
>> false);
>>          if (ER.isInvalid())
>>            return StmtError();
>>          RetValExp = ER.get();
>> @@ -3751,7 +3737,8 @@ StmtResult Sema::BuildReturnStmt(SourceL
>>      }
>>
>>      if (RetValExp) {
>> -      ExprResult ER = ActOnFinishFullExpr(RetValExp, ReturnLoc);
>> +      ExprResult ER =
>> +          ActOnFinishFullExpr(RetValExp, ReturnLoc, /*DiscardedValue*/
>> false);
>>        if (ER.isInvalid())
>>          return StmtError();
>>        RetValExp = ER.get();
>> @@ -3804,7 +3791,7 @@ StmtResult Sema::BuildObjCAtThrowStmt(So
>>      if (Result.isInvalid())
>>        return StmtError();
>>
>> -    Result = ActOnFinishFullExpr(Result.get());
>> +    Result = ActOnFinishFullExpr(Result.get(), /*DiscardedValue*/ false);
>>      if (Result.isInvalid())
>>        return StmtError();
>>      Throw = Result.get();
>> @@ -3876,7 +3863,7 @@ Sema::ActOnObjCAtSynchronizedOperand(Sou
>>    }
>>
>>    // The operand to @synchronized is a full-expression.
>> -  return ActOnFinishFullExpr(operand);
>> +  return ActOnFinishFullExpr(operand, /*DiscardedValue*/ false);
>>  }
>>
>>  StmtResult
>>
>> Modified: cfe/trunk/lib/Sema/TreeTransform.h
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/TreeTransform.h?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Sema/TreeTransform.h (original)
>> +++ cfe/trunk/lib/Sema/TreeTransform.h Fri Jan  4 08:58:14 2019
>> @@ -328,7 +328,7 @@ public:
>>    /// other mechanism.
>>    ///
>>    /// \returns the transformed statement.
>> -  StmtResult TransformStmt(Stmt *S);
>> +  StmtResult TransformStmt(Stmt *S, bool DiscardedValue = false);
>>
>>    /// Transform the given statement.
>>    ///
>> @@ -3269,8 +3269,8 @@ private:
>>                                        bool DeducibleTSTContext);
>>  };
>>
>> -template<typename Derived>
>> -StmtResult TreeTransform<Derived>::TransformStmt(Stmt *S) {
>> +template <typename Derived>
>> +StmtResult TreeTransform<Derived>::TransformStmt(Stmt *S, bool
>> DiscardedValue) {
>>    if (!S)
>>      return S;
>>
>> @@ -3294,7 +3294,7 @@ StmtResult TreeTransform<Derived>::Trans
>>        if (E.isInvalid())
>>          return StmtError();
>>
>> -      return getSema().ActOnExprStmt(E);
>> +      return getSema().ActOnExprStmt(E, DiscardedValue);
>>      }
>>    }
>>
>> @@ -4715,7 +4715,8 @@ TreeTransform<Derived>::TransformVariabl
>>    }
>>    if (SizeResult.isInvalid())
>>      return QualType();
>> -  SizeResult = SemaRef.ActOnFinishFullExpr(SizeResult.get());
>> +  SizeResult =
>> +      SemaRef.ActOnFinishFullExpr(SizeResult.get(), /*DiscardedValue*/
>> false);
>>    if (SizeResult.isInvalid())
>>      return QualType();
>>
>> @@ -6520,7 +6521,9 @@ TreeTransform<Derived>::TransformCompoun
>>    bool SubStmtChanged = false;
>>    SmallVector<Stmt*, 8> Statements;
>>    for (auto *B : S->body()) {
>> -    StmtResult Result = getDerived().TransformStmt(B);
>> +    StmtResult Result =
>> +        getDerived().TransformStmt(B, !IsStmtExpr || B !=
>> S->body_back());
>> +
>>      if (Result.isInvalid()) {
>>        // Immediately fail if this was a DeclStmt, since it's very
>>        // likely that this will cause problems for future statements.
>>
>> Modified: cfe/trunk/test/CXX/stmt.stmt/stmt.select/p3.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/stmt.stmt/stmt.select/p3.cpp?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/CXX/stmt.stmt/stmt.select/p3.cpp (original)
>> +++ cfe/trunk/test/CXX/stmt.stmt/stmt.select/p3.cpp Fri Jan  4 08:58:14
>> 2019
>> @@ -1,5 +1,5 @@
>> -// RUN: %clang_cc1 -fsyntax-only -verify %s
>> -// RUN: %clang_cc1 -fsyntax-only -std=c++1z -Wc++14-compat -verify %s
>> -DCPP17
>> +// RUN: %clang_cc1 -fsyntax-only -Wno-unused-value -verify %s
>> +// RUN: %clang_cc1 -fsyntax-only -Wno-unused-value -std=c++1z
>> -Wc++14-compat -verify %s -DCPP17
>>
>>  int f();
>>
>> @@ -71,7 +71,6 @@ void whileInitStatement() {
>>  // last loop above. It would be nice to remove this.
>>  void whileInitStatement2() {
>>    while (; false) {} // expected-error {{expected expression}}
>> -  // expected-warning at -1 {{expression result unused}}
>> -  // expected-error at -2 {{expected ';' after expression}}
>> -  // expected-error at -3 {{expected expression}}
>> +  // expected-error at -1 {{expected ';' after expression}}
>> +  // expected-error at -2 {{expected expression}}
>>  }
>>
>> Modified: cfe/trunk/test/CodeCompletion/pragma-macro-token-caching.c
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeCompletion/pragma-macro-token-caching.c?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/CodeCompletion/pragma-macro-token-caching.c (original)
>> +++ cfe/trunk/test/CodeCompletion/pragma-macro-token-caching.c Fri Jan  4
>> 08:58:14 2019
>> @@ -12,7 +12,7 @@ void completeParam(int param) {
>>
>>  void completeParamPragmaError(int param) {
>>      Outer(__extension__({ _Pragma(2) })); // expected-error {{_Pragma
>> takes a parenthesized string literal}}
>> -    param;
>> +    param; // expected-warning {{expression result unused}}
>>  }
>>
>>  // RUN: %clang_cc1 -fsyntax-only -verify -code-completion-at=%s:16:1 %s
>> | FileCheck %s
>>
>> Modified: cfe/trunk/test/Parser/cxx1z-init-statement.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Parser/cxx1z-init-statement.cpp?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/Parser/cxx1z-init-statement.cpp (original)
>> +++ cfe/trunk/test/Parser/cxx1z-init-statement.cpp Fri Jan  4 08:58:14
>> 2019
>> @@ -13,9 +13,9 @@ int f() {
>>    if (T(n) = 0; n) {}
>>
>>    // init-statement expressions
>> -  if (T{f()}; f()) {}
>> -  if (T{f()}, g, h; f()) {} // expected-warning 2{{unused}}
>> -  if (T(f()), g, h + 1; f()) {} // expected-warning 2{{unused}}
>> +  if (T{f()}; f()) {} // expected-warning {{expression result unused}}
>> +  if (T{f()}, g, h; f()) {} // expected-warning 2{{unused}}
>> expected-warning {{expression result unused}}
>> +  if (T(f()), g, h + 1; f()) {} // expected-warning 2{{unused}}
>> expected-warning {{expression result unused}}
>>
>>    // condition declarations
>>    if (T(n){g}) {}
>> @@ -35,7 +35,7 @@ int f() {
>>
>>    // Likewise for 'switch'
>>    switch (int n; n) {}
>> -  switch (g; int g = 5) {}
>> +  switch (g; int g = 5) {} // expected-warning {{expression result
>> unused}}
>>
>>    if (int a, b; int c = a) { // expected-note 6{{previous}}
>>      int a; // expected-error {{redefinition}}
>>
>> Modified: cfe/trunk/test/Parser/switch-recovery.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Parser/switch-recovery.cpp?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/Parser/switch-recovery.cpp (original)
>> +++ cfe/trunk/test/Parser/switch-recovery.cpp Fri Jan  4 08:58:14 2019
>> @@ -105,7 +105,7 @@ void test9(int x) { // expected-note {{'
>>                expected-error {{expected expression}}
>>      8:: x; // expected-error {{expected ';' after expression}} \
>>                expected-error {{no member named 'x' in the global
>> namespace; did you mean simply 'x'?}} \
>> -              expected-warning 2 {{expression result unused}}
>> +              expected-warning {{expression result unused}}
>>      9:: :y; // expected-error {{expected ';' after expression}} \
>>                 expected-error {{expected unqualified-id}} \
>>                 expected-warning {{expression result unused}}
>>
>> Modified: cfe/trunk/test/SemaCXX/cxx1z-init-statement.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/cxx1z-init-statement.cpp?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/SemaCXX/cxx1z-init-statement.cpp (original)
>> +++ cfe/trunk/test/SemaCXX/cxx1z-init-statement.cpp Fri Jan  4 08:58:14
>> 2019
>> @@ -1,5 +1,5 @@
>> -// RUN: %clang_cc1 -std=c++1z -verify %s
>> -// RUN: %clang_cc1 -std=c++17 -verify %s
>> +// RUN: %clang_cc1 -std=c++1z -Wno-unused-value -verify %s
>> +// RUN: %clang_cc1 -std=c++17 -Wno-unused-value -verify %s
>>
>>  void testIf() {
>>    int x = 0;
>> @@ -12,7 +12,7 @@ void testIf() {
>>      int x = 0; // expected-error {{redefinition of 'x'}}
>>
>>    if (x; int a = 0) ++a;
>> -  if (x, +x; int a = 0) // expected-note 2 {{previous definition is
>> here}} expected-warning {{unused}}
>> +  if (x, +x; int a = 0) // expected-note 2 {{previous definition is
>> here}}
>>      int a = 0; // expected-error {{redefinition of 'a'}}
>>    else
>>      int a = 0; // expected-error {{redefinition of 'a'}}
>> @@ -48,7 +48,7 @@ void testSwitch() {
>>        ++a;
>>    }
>>
>> -  switch (x, +x; int a = 0) { // expected-note {{previous definition is
>> here}} expected-warning {{unused}}
>> +  switch (x, +x; int a = 0) { // expected-note {{previous definition is
>> here}}
>>      case 0:
>>        int a = 0; // expected-error {{redefinition of 'a'}} //
>> expected-note {{previous definition is here}}
>>      case 1:
>>
>> Modified: cfe/trunk/test/SemaCXX/for-range-examples.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/for-range-examples.cpp?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/SemaCXX/for-range-examples.cpp (original)
>> +++ cfe/trunk/test/SemaCXX/for-range-examples.cpp Fri Jan  4 08:58:14 2019
>> @@ -244,7 +244,7 @@ void foo ()
>>  {
>>    int b = 1, a[b];
>>    a[0] = 0;
>> -  [&] { for (int c : a) 0; } ();
>> +  [&] { for (int c : a) 0; } (); // expected-warning {{expression result
>> unused}}
>>  }
>>
>>
>>
>> Modified: cfe/trunk/test/SemaCXX/warn-unused-result.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/warn-unused-result.cpp?rev=350404&r1=350403&r2=350404&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/SemaCXX/warn-unused-result.cpp (original)
>> +++ cfe/trunk/test/SemaCXX/warn-unused-result.cpp Fri Jan  4 08:58:14 2019
>> @@ -33,6 +33,36 @@ void test() {
>>    const S &s4 = g1();
>>  }
>>
>> +void testSubstmts(int i) {
>> +  switch (i) {
>> +  case 0:
>> +    f(); // expected-warning {{ignoring return value}}
>> +  default:
>> +    f(); // expected-warning {{ignoring return value}}
>> +  }
>> +
>> +  if (i)
>> +    f(); // expected-warning {{ignoring return value}}
>> +  else
>> +    f(); // expected-warning {{ignoring return value}}
>> +
>> +  while (i)
>> +    f(); // expected-warning {{ignoring return value}}
>> +
>> +  do
>> +    f(); // expected-warning {{ignoring return value}}
>> +  while (i);
>> +
>> +  for (f(); // expected-warning {{ignoring return value}}
>> +       ;
>> +       f() // expected-warning {{ignoring return value}}
>> +      )
>> +    f(); // expected-warning {{ignoring return value}}
>> +
>> +  f(),  // expected-warning {{ignoring return value}}
>> +  (void)f();
>> +}
>> +
>>  struct X {
>>   int foo() __attribute__((warn_unused_result));
>>  };
>> @@ -206,3 +236,13 @@ void f() {
>>    (void)++p;
>>  }
>>  } // namespace
>> +
>> +namespace PR39837 {
>> +[[clang::warn_unused_result]] int f(int);
>> +
>> +void g() {
>> +  int a[2];
>> +  for (int b : a)
>> +    f(b); // expected-warning {{ignoring return value}}
>> +}
>> +} // namespace PR39837
>>
>>
>> _______________________________________________
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>> cfe-commits at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
>>
> _______________________________________________
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