Commit 98532e41 authored by Tom Stellard's avatar Tom Stellard
Browse files

Merging r310905 and r310994: 

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r310905 | rnk | 2017-08-14 18:17:47 -0700 (Mon, 14 Aug 2017) | 11 lines

Avoid PointerIntPair of constexpr EvalInfo structs

They are stack allocated, so their alignment is not to be trusted.
32-bit MSVC only guarantees 4 byte stack alignment, even though alignof
would tell you otherwise. I tried fixing this with __declspec align, but
that apparently upsets GCC. Hopefully this version will satisfy all
compilers.

See PR32018 for some info about the mingw issues.

Should supercede https://reviews.llvm.org/D34873
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r310994 | chandlerc | 2017-08-16 00:22:49 -0700 (Wed, 16 Aug 2017) | 6 lines

Fix a UBSan failure where this boolean was copied when uninitialized.

When r310905 moved the pointer and bool out of a PointerIntPair, it made
them end up uninitialized and caused UBSan failures when copying the
uninitialized boolean. However, making the pointer be null should avoid
the reference to the boolean entirely.
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llvm-svn: 318225
parent 9ad76aac

clang/lib/AST/ExprConstant.cpp

+11 −13
Original line number Diff line number Diff line
@@ -537,7 +537,7 @@ namespace { 
  /// rules.  For example, the RHS of (0 && foo()) is not evaluated.  We can

  /// evaluate the expression regardless of what the RHS is, but C only allows

  /// certain things in certain situations.

  struct LLVM_ALIGNAS(/*alignof(uint64_t)*/ 8) EvalInfo {

  struct EvalInfo {

    ASTContext &Ctx;



    /// EvalStatus - Contains information about the evaluation.
@@ -977,24 +977,22 @@ namespace { 
  /// RAII object used to optionally suppress diagnostics and side-effects from

  /// a speculative evaluation.

  class SpeculativeEvaluationRAII {

    /// Pair of EvalInfo, and a bit that stores whether or not we were

    /// speculatively evaluating when we created this RAII.

    llvm::PointerIntPair<EvalInfo *, 1, bool> InfoAndOldSpecEval;

    Expr::EvalStatus Old;

    EvalInfo *Info = nullptr;

    Expr::EvalStatus OldStatus;

    bool OldIsSpeculativelyEvaluating;



    void moveFromAndCancel(SpeculativeEvaluationRAII &&Other) {

      InfoAndOldSpecEval = Other.InfoAndOldSpecEval;

      Old = Other.Old;

      Other.InfoAndOldSpecEval.setPointer(nullptr);

      Info = Other.Info;

      OldStatus = Other.OldStatus;

      Other.Info = nullptr;

    }



    void maybeRestoreState() {

      EvalInfo *Info = InfoAndOldSpecEval.getPointer();

      if (!Info)

        return;



      Info->EvalStatus = Old;

      Info->IsSpeculativelyEvaluating = InfoAndOldSpecEval.getInt();

      Info->EvalStatus = OldStatus;

      Info->IsSpeculativelyEvaluating = OldIsSpeculativelyEvaluating;

    }



  public:
@@ -1002,8 +1000,8 @@ namespace { 


    SpeculativeEvaluationRAII(

        EvalInfo &Info, SmallVectorImpl<PartialDiagnosticAt> *NewDiag = nullptr)

        : InfoAndOldSpecEval(&Info, Info.IsSpeculativelyEvaluating),

          Old(Info.EvalStatus) {

        : Info(&Info), OldStatus(Info.EvalStatus),

          OldIsSpeculativelyEvaluating(Info.IsSpeculativelyEvaluating) {

      Info.EvalStatus.Diag = NewDiag;

      Info.IsSpeculativelyEvaluating = true;

    }