george.burgess.iv updated this revision to Diff 36972.
george.burgess.iv marked 4 inline comments as done.
george.burgess.iv added a comment.
Addressed all feedback.
Also, updated object-size tests to use CHECK-LABEL instead of CHECK, because
yay I’m learning how to do things properly.
http://reviews.llvm.org/D12821
Files:
lib/AST/ExprConstant.cpp
test/CodeGen/object-size.c
test/CodeGen/object-size.cpp
Index: test/CodeGen/object-size.cpp
===================================================================
--- test/CodeGen/object-size.cpp
+++ test/CodeGen/object-size.cpp
@@ -28,3 +28,37 @@
// CHECK: store i32 4
gi = __builtin_object_size((char*)(B*)&c, 0);
}
+
+// CHECK-LABEL: define void @_Z5test2v()
+void test2() {
+ struct A { char buf[16]; };
+ struct B : A {};
+ struct C { int i; B bs[1]; } *c;
+
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(&c->bs[0], 0);
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(&c->bs[0], 1);
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 true)
+ gi = __builtin_object_size(&c->bs[0], 2);
+ // CHECK: store i32 16
+ gi = __builtin_object_size(&c->bs[0], 3);
+
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size((A*)&c->bs[0], 0);
+ // CHECK: store i32 16
+ gi = __builtin_object_size((A*)&c->bs[0], 1);
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 true)
+ gi = __builtin_object_size((A*)&c->bs[0], 2);
+ // CHECK: store i32 16
+ gi = __builtin_object_size((A*)&c->bs[0], 3);
+
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(&c->bs[0].buf[0], 0);
+ // CHECK: store i32 16
+ gi = __builtin_object_size(&c->bs[0].buf[0], 1);
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 true)
+ gi = __builtin_object_size(&c->bs[0].buf[0], 2);
+ // CHECK: store i32 16
+ gi = __builtin_object_size(&c->bs[0].buf[0], 3);
+}
Index: test/CodeGen/object-size.c
===================================================================
--- test/CodeGen/object-size.c
+++ test/CodeGen/object-size.c
@@ -127,7 +127,7 @@
strcpy(gp += 1, "Hi there");
}
-// CHECK: @test17
+// CHECK-LABEL: @test17
void test17() {
// CHECK: store i32 -1
gi = __builtin_object_size(gp++, 0);
@@ -139,15 +139,15 @@
gi = __builtin_object_size(gp++, 3);
}
-// CHECK: @test18
+// CHECK-LABEL: @test18
unsigned test18(int cond) {
int a[4], b[4];
// CHECK: phi i32*
// CHECK: call i64 @llvm.objectsize.i64
return __builtin_object_size(cond ? a : b, 0);
}
-// CHECK: @test19
+// CHECK-LABEL: @test19
void test19() {
struct {
int a, b;
@@ -172,7 +172,7 @@
gi = __builtin_object_size(&foo.b, 3);
}
-// CHECK: @test20
+// CHECK-LABEL: @test20
void test20() {
struct { int t[10]; } t[10];
@@ -186,7 +186,7 @@
gi = __builtin_object_size(&t[0].t[5], 3);
}
-// CHECK: @test21
+// CHECK-LABEL: @test21
void test21() {
struct { int t; } t;
@@ -209,7 +209,7 @@
gi = __builtin_object_size(&t.t + 1, 3);
}
-// CHECK: @test22
+// CHECK-LABEL: @test22
void test22() {
struct { int t[10]; } t[10];
@@ -252,7 +252,7 @@
struct Test23Ty { int a; int t[10]; };
-// CHECK: @test23
+// CHECK-LABEL: @test23
void test23(struct Test23Ty *p) {
// CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
gi = __builtin_object_size(p, 0);
@@ -285,7 +285,7 @@
}
// PR24493 -- ICE if __builtin_object_size called with NULL and (Type & 1) != 0
-// CHECK: @test24
+// CHECK-LABEL: @test24
void test24() {
// CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* {{.*}}, i1 false)
gi = __builtin_object_size((void*)0, 0);
@@ -299,7 +299,7 @@
gi = __builtin_object_size((void*)0, 3);
}
-// CHECK: @test25
+// CHECK-LABEL: @test25
void test25() {
// CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* {{.*}}, i1 false)
gi = __builtin_object_size((void*)0x1000, 0);
@@ -324,7 +324,7 @@
gi = __builtin_object_size((void*)0 + 0x1000, 3);
}
-// CHECK: @test26
+// CHECK-LABEL: @test26
void test26() {
struct { int v[10]; } t[10];
@@ -340,7 +340,7 @@
struct Test27IncompleteTy;
-// CHECK: @test27
+// CHECK-LABEL: @test27
void test27(struct Test27IncompleteTy *t) {
// CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
gi = __builtin_object_size(t, 0);
@@ -367,7 +367,7 @@
// The intent of this test is to ensure that __builtin_object_size treats `&foo`
// and `(T*)&foo` identically, when used as the pointer argument.
-// CHECK: @test28
+// CHECK-LABEL: @test28
void test28() {
struct { int v[10]; } t[10];
@@ -391,3 +391,129 @@
gi = __builtin_object_size(addCasts(&t[1].v[1]), 3);
#undef addCasts
}
+
+struct DynStructVar {
+ char fst[16];
+ char snd[];
+};
+
+struct DynStruct0 {
+ char fst[16];
+ char snd[0];
+};
+
+struct DynStruct1 {
+ char fst[16];
+ char snd[1];
+};
+
+struct StaticStruct {
+ char fst[16];
+ char snd[2];
+};
+
+// CHECK-LABEL: @test29
+void test29(struct DynStructVar *dv, struct DynStruct0 *d0,
+ struct DynStruct1 *d1, struct StaticStruct *ss) {
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(dv->snd, 0);
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(dv->snd, 1);
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 true)
+ gi = __builtin_object_size(dv->snd, 2);
+ // CHECK: store i32 0
+ gi = __builtin_object_size(dv->snd, 3);
+
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(d0->snd, 0);
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(d0->snd, 1);
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 true)
+ gi = __builtin_object_size(d0->snd, 2);
+ // CHECK: store i32 0
+ gi = __builtin_object_size(d0->snd, 3);
+
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(d1->snd, 0);
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(d1->snd, 1);
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 true)
+ gi = __builtin_object_size(d1->snd, 2);
+ // CHECK: store i32 1
+ gi = __builtin_object_size(d1->snd, 3);
+
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(ss->snd, 0);
+ // CHECK: store i32 2
+ gi = __builtin_object_size(ss->snd, 1);
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 true)
+ gi = __builtin_object_size(ss->snd, 2);
+ // CHECK: store i32 2
+ gi = __builtin_object_size(ss->snd, 3);
+}
+
+// CHECK-LABEL: @test30
+void test30() {
+ struct { struct DynStruct1 fst, snd; } *nested;
+
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(nested->fst.snd, 0);
+ // CHECK: store i32 1
+ gi = __builtin_object_size(nested->fst.snd, 1);
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 true)
+ gi = __builtin_object_size(nested->fst.snd, 2);
+ // CHECK: store i32 1
+ gi = __builtin_object_size(nested->fst.snd, 3);
+
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(nested->snd.snd, 0);
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(nested->snd.snd, 1);
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 true)
+ gi = __builtin_object_size(nested->snd.snd, 2);
+ // CHECK: store i32 1
+ gi = __builtin_object_size(nested->snd.snd, 3);
+
+ union { struct DynStruct1 d1; char c[1]; } *u;
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(u->c, 0);
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(u->c, 1);
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 true)
+ gi = __builtin_object_size(u->c, 2);
+ // CHECK: store i32 1
+ gi = __builtin_object_size(u->c, 3);
+
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(u->d1.snd, 0);
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(u->d1.snd, 1);
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 true)
+ gi = __builtin_object_size(u->d1.snd, 2);
+ // CHECK: store i32 1
+ gi = __builtin_object_size(u->d1.snd, 3);
+}
+
+// CHECK-LABEL: @test31
+void test31() {
+ // Miscellaneous 'writing off the end' detection tests
+ struct DynStructVar *dsv;
+ struct DynStruct0 *ds0;
+ struct DynStruct1 *ds1;
+ struct StaticStruct *ss;
+
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(ds1[9].snd, 1);
+
+ // CHECH: store i32 2
+ gi = __builtin_object_size(&ss[9].snd[0], 1);
+
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(&ds1[9].snd[0], 1);
+
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(&ds0[9].snd[0], 1);
+
+ // CHECK: call i64 @llvm.objectsize.i64.p0i8(i8* %{{.*}}, i1 false)
+ gi = __builtin_object_size(&dsv[9].snd[0], 1);
+}
Index: lib/AST/ExprConstant.cpp
===================================================================
--- lib/AST/ExprConstant.cpp
+++ lib/AST/ExprConstant.cpp
@@ -114,7 +114,8 @@
static
unsigned findMostDerivedSubobject(ASTContext &Ctx, QualType Base,
ArrayRef<APValue::LValuePathEntry> Path,
- uint64_t &ArraySize, QualType &Type) {
+ uint64_t &ArraySize, QualType &Type,
+ bool &IsArray) {
unsigned MostDerivedLength = 0;
Type = Base;
for (unsigned I = 0, N = Path.size(); I != N; ++I) {
@@ -124,18 +125,22 @@
Type = CAT->getElementType();
ArraySize = CAT->getSize().getZExtValue();
MostDerivedLength = I + 1;
+ IsArray = true;
} else if (Type->isAnyComplexType()) {
const ComplexType *CT = Type->castAs<ComplexType>();
Type = CT->getElementType();
ArraySize = 2;
MostDerivedLength = I + 1;
+ IsArray = true;
} else if (const FieldDecl *FD = getAsField(Path[I])) {
Type = FD->getType();
ArraySize = 0;
MostDerivedLength = I + 1;
+ IsArray = false;
} else {
// Path[I] describes a base class.
ArraySize = 0;
+ IsArray = false;
}
}
return MostDerivedLength;
@@ -157,12 +162,17 @@
/// Is this a pointer one past the end of an object?
bool IsOnePastTheEnd : 1;
+ /// Indicator of whether the most-derived object is an array element.
+ bool MostDerivedIsArrayElement : 1;
+
/// The length of the path to the most-derived object of which this is a
/// subobject.
- unsigned MostDerivedPathLength : 30;
+ unsigned MostDerivedPathLength : 29;
- /// The size of the array of which the most-derived object is an element, or
- /// 0 if the most-derived object is not an array element.
+ /// The size of the array of which the most-derived object is an element.
+ /// This will always be 0 if the most-derived object is not an array
+ /// element. 0 is not an indicator of whether or not the most-derived object
+ /// is an array, however, because 0-length arrays are allowed.
uint64_t MostDerivedArraySize;
/// The type of the most derived object referred to by this address.
@@ -176,21 +186,26 @@
SubobjectDesignator() : Invalid(true) {}
explicit SubobjectDesignator(QualType T)
- : Invalid(false), IsOnePastTheEnd(false), MostDerivedPathLength(0),
- MostDerivedArraySize(0), MostDerivedType(T) {}
+ : Invalid(false), IsOnePastTheEnd(false),
+ MostDerivedIsArrayElement(false), MostDerivedPathLength(0),
+ MostDerivedArraySize(0), MostDerivedType(T) {}
SubobjectDesignator(ASTContext &Ctx, const APValue &V)
- : Invalid(!V.isLValue() || !V.hasLValuePath()), IsOnePastTheEnd(false),
- MostDerivedPathLength(0), MostDerivedArraySize(0) {
+ : Invalid(!V.isLValue() || !V.hasLValuePath()), IsOnePastTheEnd(false),
+ MostDerivedIsArrayElement(false), MostDerivedPathLength(0),
+ MostDerivedArraySize(0) {
if (!Invalid) {
IsOnePastTheEnd = V.isLValueOnePastTheEnd();
ArrayRef<PathEntry> VEntries = V.getLValuePath();
Entries.insert(Entries.end(), VEntries.begin(), VEntries.end());
- if (V.getLValueBase())
+ if (V.getLValueBase()) {
+ bool IsArray = false;
MostDerivedPathLength =
findMostDerivedSubobject(Ctx, getType(V.getLValueBase()),
V.getLValuePath(), MostDerivedArraySize,
- MostDerivedType);
+ MostDerivedType, IsArray);
+ MostDerivedIsArrayElement = IsArray;
+ }
}
}
@@ -204,7 +219,7 @@
assert(!Invalid);
if (IsOnePastTheEnd)
return true;
- if (MostDerivedArraySize &&
+ if (MostDerivedIsArrayElement &&
Entries[MostDerivedPathLength - 1].ArrayIndex == MostDerivedArraySize)
return true;
return false;
@@ -228,6 +243,7 @@
// This is a most-derived object.
MostDerivedType = CAT->getElementType();
+ MostDerivedIsArrayElement = true;
MostDerivedArraySize = CAT->getSize().getZExtValue();
MostDerivedPathLength = Entries.size();
}
@@ -242,6 +258,7 @@
// If this isn't a base class, it's a new most-derived object.
if (const FieldDecl *FD = dyn_cast<FieldDecl>(D)) {
MostDerivedType = FD->getType();
+ MostDerivedIsArrayElement = false;
MostDerivedArraySize = 0;
MostDerivedPathLength = Entries.size();
}
@@ -255,14 +272,16 @@
// This is technically a most-derived object, though in practice this
// is unlikely to matter.
MostDerivedType = EltTy;
+ MostDerivedIsArrayElement = true;
MostDerivedArraySize = 2;
MostDerivedPathLength = Entries.size();
}
void diagnosePointerArithmetic(EvalInfo &Info, const Expr *E, uint64_t N);
/// Add N to the address of this subobject.
void adjustIndex(EvalInfo &Info, const Expr *E, uint64_t N) {
if (Invalid) return;
- if (MostDerivedPathLength == Entries.size() && MostDerivedArraySize) {
+ if (MostDerivedPathLength == Entries.size() &&
+ MostDerivedIsArrayElement) {
Entries.back().ArrayIndex += N;
if (Entries.back().ArrayIndex > MostDerivedArraySize) {
diagnosePointerArithmetic(Info, E, Entries.back().ArrayIndex);
@@ -834,7 +853,7 @@
void SubobjectDesignator::diagnosePointerArithmetic(EvalInfo &Info,
const Expr *E, uint64_t N) {
- if (MostDerivedPathLength == Entries.size() && MostDerivedArraySize)
+ if (MostDerivedPathLength == Entries.size() && MostDerivedIsArrayElement)
Info.CCEDiag(E, diag::note_constexpr_array_index)
<< static_cast<int>(N) << /*array*/ 0
<< static_cast<unsigned>(MostDerivedArraySize);
@@ -2517,7 +2536,7 @@
if (A.Entries.size() != B.Entries.size())
return false;
- bool IsArray = A.MostDerivedArraySize != 0;
+ bool IsArray = A.MostDerivedIsArrayElement;
if (IsArray && A.MostDerivedPathLength != A.Entries.size())
// A is a subobject of the array element.
return false;
@@ -4416,7 +4435,8 @@
if (!EvalOK) {
if (!this->Info.allowInvalidBaseExpr())
return false;
- Result.setInvalid(E->getBase());
+ Result.setInvalid(E);
+ return true;
}
const ValueDecl *MD = E->getMemberDecl();
@@ -6276,6 +6296,82 @@
return ignorePointerCastsAndParens(SubExpr);
}
+/// Checks to see if the given LValue's Designator is at the end of the LValue's
+/// record layout. e.g.
+/// struct { struct { int a, b; } fst, snd; } obj;
+/// obj.fst // no
+/// obj.snd // yes
+/// obj.fst.a // no
+/// obj.fst.b // no
+/// obj.snd.a // no
+/// obj.snd.b // yes
+static bool isDesignatorAtObjectEnd(const ASTContext &Ctx, const LValue &LVal) {
+ assert(!LVal.Designator.Invalid);
+
+ auto IsLastFieldDecl = [&Ctx](const FieldDecl *FD) {
+ if (FD->getParent()->isUnion())
+ return true;
+ const ASTRecordLayout &Layout = Ctx.getASTRecordLayout(FD->getParent());
+ return FD->getFieldIndex() + 1 == Layout.getFieldCount();
+ };
+
+ auto &Base = LVal.getLValueBase();
+ if (auto *ME = dyn_cast_or_null<MemberExpr>(Base.dyn_cast<const Expr *>())) {
+ if (auto *FD = dyn_cast<FieldDecl>(ME->getMemberDecl())) {
+ if (!IsLastFieldDecl(FD))
+ return false;
+ } else if (auto *IFD = dyn_cast<IndirectFieldDecl>(ME->getMemberDecl())) {
+ for (auto *FD : IFD->chain())
+ if (!IsLastFieldDecl(cast<FieldDecl>(FD)))
+ return false;
+ }
+ }
+
+ QualType BaseType = getType(Base);
+ for (int I = 0, E = LVal.Designator.Entries.size(); I != E; ++I) {
+ if (BaseType->isArrayType()) {
+ // Because __builtin_object_size treats arrays as objects, we can ignore
+ // the index iff this is the last array in the Designator.
+ if (I + 1 == E)
+ return true;
+ auto *CAT = cast<ConstantArrayType>(Ctx.getAsArrayType(BaseType));
+ uint64_t Index = LVal.Designator.Entries[I].ArrayIndex;
+ if (Index + 1 != CAT->getSize())
+ return false;
+ BaseType = CAT->getElementType();
+ } else if (BaseType->isAnyComplexType()) {
+ auto *CT = BaseType->castAs<ComplexType>();
+ uint64_t Index = LVal.Designator.Entries[I].ArrayIndex;
+ if (Index != 1)
+ return false;
+ BaseType = CT->getElementType();
+ } else if (auto *FD = getAsField(LVal.Designator.Entries[I])) {
+ if (!IsLastFieldDecl(FD))
+ return false;
+ BaseType = FD->getType();
+ } else {
+ assert(getAsBaseClass(LVal.Designator.Entries[I]) != nullptr &&
+ "Expecting cast to a base class");
+ return false;
+ }
+ }
+ return true;
+}
+
+/// Tests to see if the has a designator (that isn't necessarily valid).
+static bool hasDesignator(const LValue &LVal) {
+ if (LVal.Designator.Invalid || !LVal.Designator.Entries.empty())
+ return true;
+
+ if (!LVal.InvalidBase)
+ return false;
+
+ auto *E = LVal.Base.dyn_cast<const Expr *>();
+ (void)E;
+ assert(E != nullptr && isa<MemberExpr>(E));
+ return true;
+}
+
bool IntExprEvaluator::TryEvaluateBuiltinObjectSize(const CallExpr *E,
unsigned Type) {
// Determine the denoted object.
@@ -6299,8 +6395,7 @@
// In the case where we're not dealing with a subobject, we discard the
// subobject bit.
- if (!Base.Designator.Invalid && Base.Designator.Entries.empty())
- Type = Type & ~1U;
+ bool SubobjectOnly = (Type & 1) != 0 && hasDesignator(Base);
// If Type & 1 is 0, we need to be able to statically guarantee that the bytes
// exist. If we can't verify the base, then we can't do that.
@@ -6313,17 +6408,17 @@
// int b = __builtin_object_size(p->buff + 4, 2); // returns 0, not 40
//
// This matches GCC's behavior.
- if ((Type & 1) == 0 && Base.InvalidBase)
+ if (Base.InvalidBase && !SubobjectOnly)
return Error(E);
- // If Type & 1 is 0, the object in question is the complete object; reset to
- // a complete object designator in that case.
+ // If we're not examining only the subobject, then we reset to a complete
+ // object designator
//
// If Type is 1 and we've lost track of the subobject, just find the complete
// object instead. (If Type is 3, that's not correct behavior and we should
// return 0 instead.)
LValue End = Base;
- if (((Type & 1) == 0) || (End.Designator.Invalid && Type == 1)) {
+ if (!SubobjectOnly || (End.Designator.Invalid && Type == 1)) {
QualType T = getObjectType(End.getLValueBase());
if (T.isNull())
End.Designator.setInvalid();
@@ -6343,7 +6438,7 @@
// denoted by the pointer. But that's not quite right -- what we actually
// want is the size of the immediately-enclosing array, if there is one.
int64_t AmountToAdd = 1;
- if (End.Designator.MostDerivedArraySize &&
+ if (End.Designator.MostDerivedIsArrayElement &&
End.Designator.Entries.size() == End.Designator.MostDerivedPathLength) {
// We got a pointer to an array. Step to its end.
AmountToAdd = End.Designator.MostDerivedArraySize -
@@ -6363,6 +6458,24 @@
return false;
auto EndOffset = End.getLValueOffset();
+
+ // The following is a moderately common idiom in C:
+ //
+ // struct Foo { int a; char c[1]; };
+ // struct Foo *F = (struct Foo *)malloc(sizeof(struct Foo) + strlen(Bar));
+ // strcpy(&F->c[0], Bar);
+ //
+ // So, if we see that we're examining a 1-length (or 0-length) array at the
+ // end of a struct with an unknown base, we give up instead of breaking code
+ // that behaves this way. Note that we only do this when Type=1, because
+ // Type=3 is a lower bound, so answering conservatively is fine.
+ if (End.InvalidBase && SubobjectOnly && Type == 1 &&
+ End.Designator.Entries.size() == End.Designator.MostDerivedPathLength &&
+ End.Designator.MostDerivedIsArrayElement &&
+ End.Designator.MostDerivedArraySize < 2 &&
+ isDesignatorAtObjectEnd(Info.Ctx, End))
+ return false;
+
if (BaseOffset > EndOffset)
return Success(0, E);
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