zaks.anna created this revision.
zaks.anna added a reviewer: dcoughlin.
zaks.anna added subscribers: xazax.hun, cfe-commits.
Herald added a subscriber: aemerson.
The analyzer assumes that system functions will not free memory or modify the
arguments in other ways, so we assume that arguments do not escape when those
are called. However, this may lead to false positive leak errors. For example,
in code like this where the pointers added to the rb_tree are freed later on:
struct alarm_event *e = calloc(1, sizeof(*e));
<snip>
rb_tree_insert_node(&alarm_tree, e);
Add a heuristic to assume that calls to system functions taking void* arguments
allow for pointer escape.
http://reviews.llvm.org/D13488
Files:
include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h
lib/StaticAnalyzer/Checkers/MallocChecker.cpp
lib/StaticAnalyzer/Core/CallEvent.cpp
test/Analysis/Inputs/system-header-simulator.h
test/Analysis/malloc.c
Index: test/Analysis/malloc.c
===================================================================
--- test/Analysis/malloc.c
+++ test/Analysis/malloc.c
@@ -1657,6 +1657,23 @@
return p;
}
+// Some data structures may hold onto the pointer and free it later.
+void testEscapeThroughSystemCallTakingVoidPointer1(void *queue) {
+ int *data = (int *)malloc(32);
+ fake_insque(queue, data); // no warning
+}
+
+void testEscapeThroughSystemCallTakingVoidPointer2(fake_rb_tree_t *rbt) {
+ int *data = (int *)malloc(32);
+ fake_rb_tree_init(rbt, data);
+} //expected-warning{{Potential leak}}
+
+void testEscapeThroughSystemCallTakingVoidPointer3(fake_rb_tree_t *rbt) {
+ int *data = (int *)malloc(32);
+ fake_rb_tree_init(rbt, data);
+ fake_rb_tree_insert_node(rbt, data); // no warning
+}
+
// ----------------------------------------------------------------------------
// False negatives.
Index: test/Analysis/Inputs/system-header-simulator.h
===================================================================
--- test/Analysis/Inputs/system-header-simulator.h
+++ test/Analysis/Inputs/system-header-simulator.h
@@ -82,6 +82,12 @@
void fakeSystemHeaderCallInt(int *);
void fakeSystemHeaderCallIntPtr(int **);
+// Some data strauctures may hold onto the pointer and free it later.
+void fake_insque(void *, void *);
+typedef struct fake_rb_tree { void *opaque[8]; } fake_rb_tree_t;
+void fake_rb_tree_init(fake_rb_tree_t *, const void *);
+void *fake_rb_tree_insert_node(fake_rb_tree_t *, void *);
+
typedef struct __SomeStruct {
char * p;
} SomeStruct;
Index: lib/StaticAnalyzer/Core/CallEvent.cpp
===================================================================
--- lib/StaticAnalyzer/Core/CallEvent.cpp
+++ lib/StaticAnalyzer/Core/CallEvent.cpp
@@ -50,11 +50,7 @@
return ResultTy;
}
-static bool isCallbackArg(SVal V, QualType T) {
- // If the parameter is 0, it's harmless.
- if (V.isZeroConstant())
- return false;
-
+static bool isCallback(QualType T) {
// If a parameter is a block or a callback, assume it can modify pointer.
if (T->isBlockPointerType() ||
T->isFunctionPointerType() ||
@@ -75,32 +71,53 @@
return true;
}
}
-
return false;
}
-bool CallEvent::hasNonZeroCallbackArg() const {
+static bool isVoidPointerToNonConst(QualType T) {
+ if (const PointerType *PT = T->getAs<PointerType>()) {
+ QualType PointeeTy = PT->getPointeeType();
+ if (PointeeTy.isConstQualified())
+ return false;
+ return PointeeTy->isVoidType();
+ } else
+ return false;
+}
+
+bool CallEvent::hasNonNullArgumentsWithType(bool (*Condition)(QualType)) const {
unsigned NumOfArgs = getNumArgs();
// If calling using a function pointer, assume the function does not
- // have a callback. TODO: We could check the types of the arguments here.
+ // satisfy the callback.
+ // TODO: We could check the types of the arguments here.
if (!getDecl())
return false;
unsigned Idx = 0;
for (CallEvent::param_type_iterator I = param_type_begin(),
- E = param_type_end();
+ E = param_type_end();
I != E && Idx < NumOfArgs; ++I, ++Idx) {
if (NumOfArgs <= Idx)
break;
- if (isCallbackArg(getArgSVal(Idx), *I))
+ // If the parameter is 0, it's harmless.
+ if (getArgSVal(Idx).isZeroConstant())
+ continue;
+
+ if (Condition(*I))
return true;
}
-
return false;
}
+bool CallEvent::hasNonZeroCallbackArg() const {
+ return hasNonNullArgumentsWithType(isCallback);
+}
+
+bool CallEvent::hasVoidPointerToNonConstArg() const {
+ return hasNonNullArgumentsWithType(isVoidPointerToNonConst);
+}
+
bool CallEvent::isGlobalCFunction(StringRef FunctionName) const {
const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(getDecl());
if (!FD)
@@ -326,7 +343,7 @@
}
bool AnyFunctionCall::argumentsMayEscape() const {
- if (hasNonZeroCallbackArg())
+ if (CallEvent::argumentsMayEscape() || hasVoidPointerToNonConstArg())
return true;
const FunctionDecl *D = getDecl();
Index: lib/StaticAnalyzer/Checkers/MallocChecker.cpp
===================================================================
--- lib/StaticAnalyzer/Checkers/MallocChecker.cpp
+++ lib/StaticAnalyzer/Checkers/MallocChecker.cpp
@@ -2390,7 +2390,7 @@
if (const ObjCMethodCall *Msg = dyn_cast<ObjCMethodCall>(Call)) {
// If it's not a framework call, or if it takes a callback, assume it
// can free memory.
- if (!Call->isInSystemHeader() || Call->hasNonZeroCallbackArg())
+ if (!Call->isInSystemHeader() || Call->argumentsMayEscape())
return true;
// If it's a method we know about, handle it explicitly post-call.
Index: include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h
===================================================================
--- include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h
+++ include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h
@@ -253,9 +253,16 @@
/// which the return value has already been bound to the origin expression.
SVal getReturnValue() const;
+ /// \brief Returns true if the type of any of the non-null arguments satisfies
+ /// the condition.
+ bool hasNonNullArgumentsWithType(bool (*Condition)(QualType)) const;
+
/// \brief Returns true if any of the arguments appear to represent callbacks.
bool hasNonZeroCallbackArg() const;
+ /// \brief Returns true if any of the arguments is void*.
+ bool hasVoidPointerToNonConstArg() const;
+
/// \brief Returns true if any of the arguments are known to escape to long-
/// term storage, even if this method will not modify them.
// NOTE: The exact semantics of this are still being defined!
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