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[analyzer] Fix null pointer deref in CastValueChecker
A crash was seen in CastValueChecker due to a null pointer dereference. The fix uses QualType::getAsString to avoid the null dereference when a CXXRecordDecl cannot be obtained. A small reproducer is added, and cast value notes LITs are updated for the new debug messages. Reviewed By: steakhal Differential Revision: https://reviews.llvm.org/D127105
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‎clang/lib/StaticAnalyzer/Checkers/CastValueChecker.cpp‎

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -108,7 +108,7 @@ static const NoteTag *getNoteTag(CheckerContext &C,
108108
bool CastSucceeds, bool IsKnownCast) {
109109
std::string CastToName =
110110
CastInfo ? CastInfo->to()->getAsCXXRecordDecl()->getNameAsString()
111-
: CastToTy->getPointeeCXXRecordDecl()->getNameAsString();
111+
: CastToTy.getAsString();
112112
Object = Object->IgnoreParenImpCasts();
113113

114114
return C.getNoteTag(
@@ -163,9 +163,9 @@ static const NoteTag *getNoteTag(CheckerContext &C,
163163
bool First = true;
164164
for (QualType CastToTy: CastToTyVec) {
165165
std::string CastToName =
166-
CastToTy->getAsCXXRecordDecl() ?
167-
CastToTy->getAsCXXRecordDecl()->getNameAsString() :
168-
CastToTy->getPointeeCXXRecordDecl()->getNameAsString();
166+
CastToTy->getAsCXXRecordDecl()
167+
? CastToTy->getAsCXXRecordDecl()->getNameAsString()
168+
: CastToTy.getAsString();
169169
Out << ' ' << ((CastToTyVec.size() == 1) ? "not" :
170170
(First ? "neither" : "nor")) << " a '" << CastToName
171171
<< '\'';

‎clang/test/Analysis/cast-value-notes.cpp‎

Lines changed: 46 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -73,7 +73,7 @@ void clang_analyzer_printState();
7373
#if defined(X86)
7474
void evalReferences(const Shape &S) {
7575
const auto &C = dyn_cast<Circle>(S);
76-
// expected-note@-1 {{Assuming 'S' is not a 'Circle'}}
76+
// expected-note@-1 {{Assuming 'S' is not a 'const class clang::Circle &'}}
7777
// expected-note@-2 {{Dereference of null pointer}}
7878
// expected-warning@-3 {{Dereference of null pointer}}
7979
clang_analyzer_printState();
@@ -93,7 +93,7 @@ void evalReferences_addrspace(const Shape &S) {
9393
#if defined(NOT_SUPPRESSED)
9494
void evalReferences_addrspace(const Shape &S) {
9595
const auto &C = dyn_cast<DEVICE Circle>(S);
96-
// expected-note@-1 {{Assuming 'S' is not a 'Circle'}}
96+
// expected-note@-1 {{Assuming 'S' is not a 'const __attribute__((address_space(3))) class clang::Circle &'}}
9797
// expected-note@-2 {{Dereference of null pointer}}
9898
// expected-warning@-3 {{Dereference of null pointer}}
9999
clang_analyzer_printState();
@@ -105,7 +105,7 @@ void evalReferences_addrspace(const Shape &S) {
105105
#elif defined(MIPS)
106106
void evalReferences(const Shape &S) {
107107
const auto &C = dyn_cast<Circle>(S);
108-
// expected-note@-1 {{Assuming 'S' is not a 'Circle'}}
108+
// expected-note@-1 {{Assuming 'S' is not a 'const class clang::Circle &'}}
109109
// expected-note@-2 {{Dereference of null pointer}}
110110
// expected-warning@-3 {{Dereference of null pointer}}
111111
}
@@ -122,25 +122,25 @@ void evalNonNullParamNonNullReturnReference(const Shape &S) {
122122
// expected-note@-1 {{'C' initialized here}}
123123

124124
if (!dyn_cast_or_null<Circle>(C)) {
125-
// expected-note@-1 {{'C' is a 'Circle'}}
125+
// expected-note@-1 {{Assuming 'C' is a 'const class clang::Circle *'}}
126126
// expected-note@-2 {{Taking false branch}}
127127
return;
128128
}
129129

130130
if (dyn_cast_or_null<Triangle>(C)) {
131-
// expected-note@-1 {{Assuming 'C' is not a 'Triangle'}}
131+
// expected-note@-1 {{Assuming 'C' is not a 'const class clang::Triangle *'}}
132132
// expected-note@-2 {{Taking false branch}}
133133
return;
134134
}
135135

136136
if (dyn_cast_or_null<Rectangle>(C)) {
137-
// expected-note@-1 {{Assuming 'C' is not a 'Rectangle'}}
137+
// expected-note@-1 {{Assuming 'C' is not a 'const class clang::Rectangle *'}}
138138
// expected-note@-2 {{Taking false branch}}
139139
return;
140140
}
141141

142142
if (dyn_cast_or_null<Hexagon>(C)) {
143-
// expected-note@-1 {{Assuming 'C' is not a 'Hexagon'}}
143+
// expected-note@-1 {{Assuming 'C' is not a 'const class clang::Hexagon *'}}
144144
// expected-note@-2 {{Taking false branch}}
145145
return;
146146
}
@@ -176,29 +176,29 @@ void evalNonNullParamNonNullReturnReference(const Shape &S) {
176176

177177
void evalNonNullParamNonNullReturn(const Shape *S) {
178178
const auto *C = cast<Circle>(S);
179-
// expected-note@-1 {{'S' is a 'Circle'}}
179+
// expected-note@-1 {{'S' is a 'const class clang::Circle *'}}
180180
// expected-note@-2 {{'C' initialized here}}
181181

182182
if (!dyn_cast_or_null<Circle>(C)) {
183-
// expected-note@-1 {{'C' is a 'Circle'}}
183+
// expected-note@-1 {{Assuming 'C' is a 'const class clang::Circle *'}}
184184
// expected-note@-2 {{Taking false branch}}
185185
return;
186186
}
187187

188188
if (dyn_cast_or_null<Triangle>(C)) {
189-
// expected-note@-1 {{Assuming 'C' is not a 'Triangle'}}
189+
// expected-note@-1 {{Assuming 'C' is not a 'const class clang::Triangle *'}}
190190
// expected-note@-2 {{Taking false branch}}
191191
return;
192192
}
193193

194194
if (dyn_cast_or_null<Rectangle>(C)) {
195-
// expected-note@-1 {{Assuming 'C' is not a 'Rectangle'}}
195+
// expected-note@-1 {{Assuming 'C' is not a 'const class clang::Rectangle *'}}
196196
// expected-note@-2 {{Taking false branch}}
197197
return;
198198
}
199199

200200
if (dyn_cast_or_null<Hexagon>(C)) {
201-
// expected-note@-1 {{Assuming 'C' is not a 'Hexagon'}}
201+
// expected-note@-1 {{Assuming 'C' is not a 'const class clang::Hexagon *'}}
202202
// expected-note@-2 {{Taking false branch}}
203203
return;
204204
}
@@ -234,10 +234,10 @@ void evalNonNullParamNonNullReturn(const Shape *S) {
234234

235235
void evalNonNullParamNullReturn(const Shape *S) {
236236
const auto *C = dyn_cast_or_null<Circle>(S);
237-
// expected-note@-1 {{Assuming 'S' is not a 'Circle'}}
237+
// expected-note@-1 {{Assuming 'S' is not a 'const class clang::Circle *'}}
238238

239239
if (const auto *T = dyn_cast_or_null<Triangle>(S)) {
240-
// expected-note@-1 {{Assuming 'S' is a 'Triangle'}}
240+
// expected-note@-1 {{Assuming 'S' is a 'const class clang::Triangle *'}}
241241
// expected-note@-2 {{'T' initialized here}}
242242
// expected-note@-3 {{'T' is non-null}}
243243
// expected-note@-4 {{Taking true branch}}
@@ -261,7 +261,7 @@ void evalNullParamNullReturn(const Shape *S) {
261261

262262
void evalZeroParamNonNullReturnPointer(const Shape *S) {
263263
const auto *C = S->castAs<Circle>();
264-
// expected-note@-1 {{'S' is a 'Circle'}}
264+
// expected-note@-1 {{'S' is a 'const class clang::Circle *'}}
265265
// expected-note@-2 {{'C' initialized here}}
266266

267267
(void)(1 / !C);
@@ -282,12 +282,12 @@ void evalZeroParamNonNullReturn(const Shape &S) {
282282

283283
void evalZeroParamNullReturn(const Shape *S) {
284284
const auto &C = S->getAs<Circle>();
285-
// expected-note@-1 {{Assuming 'S' is not a 'Circle'}}
285+
// expected-note@-1 {{Assuming 'S' is not a 'const class clang::Circle *'}}
286286
// expected-note@-2 {{Storing null pointer value}}
287287
// expected-note@-3 {{'C' initialized here}}
288288

289289
if (!dyn_cast_or_null<Triangle>(S)) {
290-
// expected-note@-1 {{Assuming 'S' is a 'Triangle'}}
290+
// expected-note@-1 {{Assuming 'S' is a 'const class clang::Triangle *'}}
291291
// expected-note@-2 {{Taking false branch}}
292292
return;
293293
}
@@ -302,3 +302,32 @@ void evalZeroParamNullReturn(const Shape *S) {
302302
// expected-note@-1 {{Division by zero}}
303303
// expected-warning@-2 {{Division by zero}}
304304
}
305+
306+
// don't crash
307+
// CastValueChecker was using QualType()->getPointeeCXXRecordDecl(), in
308+
// getNoteTag which evaluated to nullptr, then crashed when attempting to
309+
// deref an invocation to getNameAsString(). The fix is to use
310+
// QualType().getAsString().
311+
//
312+
// Example:
313+
// std::string CastToName =
314+
// CastInfo ? CastInfo->to()->getAsCXXRecordDecl()->getNameAsString()
315+
// : CastToTy->getPointeeCXXRecordDecl()->getNameAsString();
316+
// Changed to:
317+
// std::string CastToName =
318+
// CastInfo ? CastInfo->to()->getAsCXXRecordDecl()->getNameAsString()
319+
// : CastToTy.getAsString();
320+
namespace llvm {
321+
template <typename, typename a> void isa(a &);
322+
template <typename> class PointerUnion {
323+
public:
324+
template <typename T> T *getAs() {
325+
(void)isa<int>(*this);
326+
return nullptr;
327+
}
328+
};
329+
class LLVMContext {
330+
PointerUnion<LLVMContext> c;
331+
void d() { c.getAs<int>(); }
332+
};
333+
} // namespace llvm

‎clang/test/Analysis/cast-value-state-dump.cpp‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -18,12 +18,12 @@ using namespace clang;
1818

1919
void evalNonNullParamNonNullReturn(const Shape *S) {
2020
const auto *C = dyn_cast_or_null<Circle>(S);
21-
// expected-note@-1 {{Assuming 'S' is a 'Circle'}}
21+
// expected-note@-1 {{Assuming 'S' is a 'const class clang::Circle *'}}
2222
// expected-note@-2 {{'C' initialized here}}
2323

2424
// FIXME: We assumed that 'S' is a 'Circle' therefore it is not a 'Square'.
2525
if (dyn_cast_or_null<Square>(S)) {
26-
// expected-note@-1 {{Assuming 'S' is not a 'Square'}}
26+
// expected-note@-1 {{Assuming 'S' is not a 'const class clang::Square *'}}
2727
// expected-note@-2 {{Taking false branch}}
2828
return;
2929
}

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