From: David Majnemer Date: Wed, 12 Feb 2014 00:43:02 +0000 (+0000) Subject: MS ABI: vptr injection should obey alignment requirements X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=10dbcf4aad39719036dc32b338ac2c111ecd00d8;p=clang MS ABI: vptr injection should obey alignment requirements vptr injection must inject padding equivalent to the alignment of the most aligned non-virtual subobject, not the alignment of the enclosing record. To fascilitate this change, don't let record layout observe the alignment of the record until we've injected our vptrs. Also, do not allow the alignment of vbases to affect required alignment until just before we insert the vtordisp field. git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@201199 91177308-0d34-0410-b5e6-96231b3b80d8 --- diff --git a/lib/AST/RecordLayoutBuilder.cpp b/lib/AST/RecordLayoutBuilder.cpp index 903f973e61..1f64b4be50 100644 --- a/lib/AST/RecordLayoutBuilder.cpp +++ b/lib/AST/RecordLayoutBuilder.cpp @@ -2277,6 +2277,8 @@ void MicrosoftRecordLayoutBuilder::layout(const RecordDecl *RD) { initializeLayout(RD); layoutFields(RD); DataSize = Size = Size.RoundUpToAlignment(Alignment); + RequiredAlignment = std::max( + RequiredAlignment, Context.toCharUnitsFromBits(RD->getMaxAlignment())); finalizeLayout(RD); } @@ -2287,6 +2289,8 @@ void MicrosoftRecordLayoutBuilder::cxxLayout(const CXXRecordDecl *RD) { layoutFields(RD); injectVPtrs(RD); DataSize = Size = Size.RoundUpToAlignment(Alignment); + RequiredAlignment = std::max( + RequiredAlignment, Context.toCharUnitsFromBits(RD->getMaxAlignment())); layoutVirtualBases(RD); finalizeLayout(RD); } @@ -2300,8 +2304,6 @@ void MicrosoftRecordLayoutBuilder::initializeLayout(const RecordDecl *RD) { // In 32-bit mode we do not. The check to see if we need to perform alignment // checks the RequiredAlignment field and performs alignment if it isn't 0. RequiredAlignment = Is64BitMode ? CharUnits::One() : CharUnits::Zero(); - RequiredAlignment = std::max(RequiredAlignment, - Context.toCharUnitsFromBits(RD->getMaxAlignment())); // Compute the maximum field alignment. MaxFieldAlignment = CharUnits::Zero(); // Honor the default struct packing maximum alignment flag. @@ -2352,14 +2354,14 @@ MicrosoftRecordLayoutBuilder::layoutNonVirtualBases(const CXXRecordDecl *RD) { i != e; ++i) { const CXXRecordDecl *BaseDecl = i->getType()->getAsCXXRecordDecl(); const ASTRecordLayout &BaseLayout = Context.getASTRecordLayout(BaseDecl); - // Track RequiredAlignment for all bases in this pass. - RequiredAlignment = std::max(RequiredAlignment, - BaseLayout.getRequiredAlignment()); // Mark and skip virtual bases. if (i->isVirtual()) { HasVBPtr = true; continue; } + // Track RequiredAlignment for all bases in this pass. + RequiredAlignment = std::max(RequiredAlignment, + BaseLayout.getRequiredAlignment()); // Check fo a base to share a VBPtr with. if (!SharedVBPtrBase && BaseLayout.hasVBPtr()) { SharedVBPtrBase = BaseDecl; @@ -2525,7 +2527,8 @@ void MicrosoftRecordLayoutBuilder::injectVBPtr(const CXXRecordDecl *RD) { CharUnits FieldStart = VBPtrOffset + PointerInfo.Size; // Make sure that the amount we push the fields back by is a multiple of the // alignment. - CharUnits Offset = (FieldStart - InjectionSite).RoundUpToAlignment(Alignment); + CharUnits Offset = (FieldStart - InjectionSite).RoundUpToAlignment( + std::max(RequiredAlignment, Alignment)); // Increase the size of the object and push back all fields by the offset // amount. Size += Offset; @@ -2547,11 +2550,12 @@ void MicrosoftRecordLayoutBuilder::injectVFPtr(const CXXRecordDecl *RD) { return; // Make sure that the amount we push the struct back by is a multiple of the // alignment. - CharUnits Offset = PointerInfo.Size.RoundUpToAlignment(Alignment); + CharUnits Offset = PointerInfo.Size.RoundUpToAlignment( + std::max(RequiredAlignment, Alignment)); // Increase the size of the object and push back all fields, the vbptr and all // bases by the offset amount. Size += Offset; - for (SmallVector::iterator i = FieldOffsets.begin(), + for (SmallVectorImpl::iterator i = FieldOffsets.begin(), e = FieldOffsets.end(); i != e; ++i) *i += Context.toBits(Offset); @@ -2646,6 +2650,14 @@ void MicrosoftRecordLayoutBuilder::layoutVirtualBases(const CXXRecordDecl *RD) { // The alignment of the vtordisp is at least the required alignment of the // entire record. This requirement may be present to support vtordisp // injection. + for (CXXRecordDecl::base_class_const_iterator i = RD->vbases_begin(), + e = RD->vbases_end(); + i != e; ++i) { + const CXXRecordDecl *BaseDecl = i->getType()->getAsCXXRecordDecl(); + const ASTRecordLayout &BaseLayout = Context.getASTRecordLayout(BaseDecl); + RequiredAlignment = + std::max(RequiredAlignment, BaseLayout.getRequiredAlignment()); + } VtorDispAlignment = std::max(VtorDispAlignment, RequiredAlignment); // Compute the vtordisp set. llvm::SmallPtrSet HasVtordispSet = diff --git a/test/Layout/ms-x86-pack-and-align.cpp b/test/Layout/ms-x86-pack-and-align.cpp index c09c363994..a9685f12e7 100644 --- a/test/Layout/ms-x86-pack-and-align.cpp +++ b/test/Layout/ms-x86-pack-and-align.cpp @@ -371,6 +371,49 @@ struct KB : KA { __declspec(align(2)) char a; }; // CHECK-X64-NEXT: | [sizeof=4, align=2 // CHECK-X64-NEXT: | nvsize=3, nvalign=2] +#pragma pack(1) +struct L { + virtual void fun() {} + __declspec(align(256)) int Field; +}; + +// CHECK: *** Dumping AST Record Layout +// CHECK-NEXT: 0 | struct L +// CHECK-NEXT: 0 | (L vftable pointer) +// CHECK-NEXT: 256 | int Field +// CHECK-NEXT: | [sizeof=512, align=256 +// CHECK-NEXT: | nvsize=260, nvalign=256] +// CHECK-X64: *** Dumping AST Record Layout +// CHECK-X64-NEXT: 0 | struct L +// CHECK-X64-NEXT: 0 | (L vftable pointer) +// CHECK-X64-NEXT: 256 | int Field +// CHECK-X64-NEXT: | [sizeof=512, align=256 +// CHECK-X64-NEXT: | nvsize=260, nvalign=256] + +#pragma pack() +struct MA {}; +#pragma pack(1) +struct MB : virtual MA { + __declspec(align(256)) int Field; +}; + +// CHECK: *** Dumping AST Record Layout +// CHECK: *** Dumping AST Record Layout +// CHECK-NEXT: 0 | struct MB +// CHECK-NEXT: 0 | (MB vbtable pointer) +// CHECK-NEXT: 256 | int Field +// CHECK-NEXT: 260 | struct MA (virtual base) (empty) +// CHECK-NEXT: | [sizeof=512, align=256 +// CHECK-NEXT: | nvsize=260, nvalign=256] +// CHECK-X64: *** Dumping AST Record Layout +// CHECK-X64: *** Dumping AST Record Layout +// CHECK-X64-NEXT: 0 | struct MB +// CHECK-X64-NEXT: 0 | (MB vbtable pointer) +// CHECK-X64-NEXT: 256 | int Field +// CHECK-X64-NEXT: 260 | struct MA (virtual base) (empty) +// CHECK-X64-NEXT: | [sizeof=512, align=256 +// CHECK-X64-NEXT: | nvsize=260, nvalign=256] + int a[ sizeof(X)+ sizeof(Y)+ @@ -387,4 +430,6 @@ sizeof(YF)+ sizeof(D2)+ sizeof(JC)+ sizeof(KB)+ +sizeof(L)+ +sizeof(MB)+ 0];