Clang Analyzer on custom shared pointer, false positive or not
0
Clang static analyzer reports a memory use after it's freed with a following implementation of the shared ptr (rather naive but still it should work fine):
template <class T>
class Shared
{
public:
Shared()
: ptr(0) , count(0)
{
}
explicit Shared(T* otherPtr)
: ptr(0), count(0)
{
init(otherPtr);
}
template <class DerivedT>
explicit Shared(DerivedT* otherPtr)
: ptr(0), count(0)
{
init(otherPtr);
}
explicit Shared(OutRef<T> ref)
: ptr(0), count(0)
{
init(ref.ptr);
}
Shared(const Shared& other)
: ptr(other.ptr), count(other.count)
{
addShared();
}
template <class DerivedT>
Shared(const Shared<DerivedT>& other)
: ptr(other.ptr), count(other.count)
{
addShared();
}
Shared& operator = (const Shared& other)
{
Shared tmp(other);
swap(tmp);
return *this;
}
template <class DerivedT>
Shared& operator = (const Shared<DerivedT>& other)
{
Shared tmp(other);
swap(tmp);
return *this;
}
~Shared()
{
destroy();
}
operator bool() const
{
return ptr != 0;
}
void operator = (T* otherPtr)
{
set(otherPtr);
}
template <class DerivedT>
void operator = (DerivedT* otherPtr)
{
set(otherPtr);
}
void operator = (OutRef<T> ref)
{
set(ref.ptr);
}
T* operator->()
{
return ptr;
}
const T* operator->() const
{
return ptr;
}
T& operator*()
{
return *ptr;
}
const T& operator*() const
{
return *ptr;
}
template <class DerivedT>
void set(DerivedT* otherPtr)
{
if (ptr != otherPtr)
{
destroy();
init(otherPtr);
}
}
T* get()
{
return ptr;
}
const T* get() const
{
return ptr;
}
operator T*()
{
return ptr;
}
operator const T*() const
{
return ptr;
}
template <class TT>
Shared<TT> cast()
{
Shared<TT> result;
result.ptr = (TT*)ptr;
result.count = count;
result.addShared();
return result;
}
bool isLastOwner() const
{
return count && *count == 1;
}
private:
void addShared()
{
if (count)
{
*count += 1;
}
}
template <class DerivedT>
void init(DerivedT* otherPtr)
{
presume(ptr == 0);
presume(count == 0);
if (otherPtr == 0)
{
return;
}
ptr = otherPtr;
count = new Index(1);
}
void destroy()
{
if (count)
{
*count -= 1;
if (*count == 0)
{
presume(sizeof(T) > 0); //will break compilation in case of undefined T
delete ptr;
delete count;
}
}
ptr = 0;
count = 0;
}
void swap(Shared& other)
{
Swap(ptr, other.ptr);
Swap(count, other.count);
}
private:
T* ptr;
Index* count;
template <class OtherT> friend class Shared;
};
For example, if I have function Shared f() and use it as
Shared<X> a = f();
a->callSomeMethod();
I get static analyzer warning that "a" is used after memory is freed. Basically it detects that destroy() method was called but cannot detect that counter is positive (it writes "Assuming condition is true" for counter zero check) in the stack trace. Is this possible to add some assert() so it understands that counter is positive here? Or may be it is really an incorrect shared pointer implementation?
c++ clang shared-ptr clang-static-analyzer
asked Nov 24 '18 at 8:40
Alexander BAlexander B
19213
add a comment |
0
Clang static analyzer reports a memory use after it's freed with a following implementation of the shared ptr (rather naive but still it should work fine):
template <class T>
class Shared
{
public:
Shared()
: ptr(0) , count(0)
{
}
explicit Shared(T* otherPtr)
: ptr(0), count(0)
{
init(otherPtr);
}
template <class DerivedT>
explicit Shared(DerivedT* otherPtr)
: ptr(0), count(0)
{
init(otherPtr);
}
explicit Shared(OutRef<T> ref)
: ptr(0), count(0)
{
init(ref.ptr);
}
Shared(const Shared& other)
: ptr(other.ptr), count(other.count)
{
addShared();
}
template <class DerivedT>
Shared(const Shared<DerivedT>& other)
: ptr(other.ptr), count(other.count)
{
addShared();
}
Shared& operator = (const Shared& other)
{
Shared tmp(other);
swap(tmp);
return *this;
}
template <class DerivedT>
Shared& operator = (const Shared<DerivedT>& other)
{
Shared tmp(other);
swap(tmp);
return *this;
}
~Shared()
{
destroy();
}
operator bool() const
{
return ptr != 0;
}
void operator = (T* otherPtr)
{
set(otherPtr);
}
template <class DerivedT>
void operator = (DerivedT* otherPtr)
{
set(otherPtr);
}
void operator = (OutRef<T> ref)
{
set(ref.ptr);
}
T* operator->()
{
return ptr;
}
const T* operator->() const
{
return ptr;
}
T& operator*()
{
return *ptr;
}
const T& operator*() const
{
return *ptr;
}
template <class DerivedT>
void set(DerivedT* otherPtr)
{
if (ptr != otherPtr)
{
destroy();
init(otherPtr);
}
}
T* get()
{
return ptr;
}
const T* get() const
{
return ptr;
}
operator T*()
{
return ptr;
}
operator const T*() const
{
return ptr;
}
template <class TT>
Shared<TT> cast()
{
Shared<TT> result;
result.ptr = (TT*)ptr;
result.count = count;
result.addShared();
return result;
}
bool isLastOwner() const
{
return count && *count == 1;
}
private:
void addShared()
{
if (count)
{
*count += 1;
}
}
template <class DerivedT>
void init(DerivedT* otherPtr)
{
presume(ptr == 0);
presume(count == 0);
if (otherPtr == 0)
{
return;
}
ptr = otherPtr;
count = new Index(1);
}
void destroy()
{
if (count)
{
*count -= 1;
if (*count == 0)
{
presume(sizeof(T) > 0); //will break compilation in case of undefined T
delete ptr;
delete count;
}
}
ptr = 0;
count = 0;
}
void swap(Shared& other)
{
Swap(ptr, other.ptr);
Swap(count, other.count);
}
private:
T* ptr;
Index* count;
template <class OtherT> friend class Shared;
};
For example, if I have function Shared f() and use it as
Shared<X> a = f();
a->callSomeMethod();
I get static analyzer warning that "a" is used after memory is freed. Basically it detects that destroy() method was called but cannot detect that counter is positive (it writes "Assuming condition is true" for counter zero check) in the stack trace. Is this possible to add some assert() so it understands that counter is positive here? Or may be it is really an incorrect shared pointer implementation?
c++ clang shared-ptr clang-static-analyzer
asked Nov 24 '18 at 8:40
Alexander BAlexander B
19213
add a comment |
0
0
0
Clang static analyzer reports a memory use after it's freed with a following implementation of the shared ptr (rather naive but still it should work fine):
template <class T>
class Shared
{
public:
Shared()
: ptr(0) , count(0)
{
}
explicit Shared(T* otherPtr)
: ptr(0), count(0)
{
init(otherPtr);
}
template <class DerivedT>
explicit Shared(DerivedT* otherPtr)
: ptr(0), count(0)
{
init(otherPtr);
}
explicit Shared(OutRef<T> ref)
: ptr(0), count(0)
{
init(ref.ptr);
}
Shared(const Shared& other)
: ptr(other.ptr), count(other.count)
{
addShared();
}
template <class DerivedT>
Shared(const Shared<DerivedT>& other)
: ptr(other.ptr), count(other.count)
{
addShared();
}
Shared& operator = (const Shared& other)
{
Shared tmp(other);
swap(tmp);
return *this;
}
template <class DerivedT>
Shared& operator = (const Shared<DerivedT>& other)
{
Shared tmp(other);
swap(tmp);
return *this;
}
~Shared()
{
destroy();
}
operator bool() const
{
return ptr != 0;
}
void operator = (T* otherPtr)
{
set(otherPtr);
}
template <class DerivedT>
void operator = (DerivedT* otherPtr)
{
set(otherPtr);
}
void operator = (OutRef<T> ref)
{
set(ref.ptr);
}
T* operator->()
{
return ptr;
}
const T* operator->() const
{
return ptr;
}
T& operator*()
{
return *ptr;
}
const T& operator*() const
{
return *ptr;
}
template <class DerivedT>
void set(DerivedT* otherPtr)
{
if (ptr != otherPtr)
{
destroy();
init(otherPtr);
}
}
T* get()
{
return ptr;
}
const T* get() const
{
return ptr;
}
operator T*()
{
return ptr;
}
operator const T*() const
{
return ptr;
}
template <class TT>
Shared<TT> cast()
{
Shared<TT> result;
result.ptr = (TT*)ptr;
result.count = count;
result.addShared();
return result;
}
bool isLastOwner() const
{
return count && *count == 1;
}
private:
void addShared()
{
if (count)
{
*count += 1;
}
}
template <class DerivedT>
void init(DerivedT* otherPtr)
{
presume(ptr == 0);
presume(count == 0);
if (otherPtr == 0)
{
return;
}
ptr = otherPtr;
count = new Index(1);
}
void destroy()
{
if (count)
{
*count -= 1;
if (*count == 0)
{
presume(sizeof(T) > 0); //will break compilation in case of undefined T
delete ptr;
delete count;
}
}
ptr = 0;
count = 0;
}
void swap(Shared& other)
{
Swap(ptr, other.ptr);
Swap(count, other.count);
}
private:
T* ptr;
Index* count;
template <class OtherT> friend class Shared;
};
For example, if I have function Shared f() and use it as
Shared<X> a = f();
a->callSomeMethod();
I get static analyzer warning that "a" is used after memory is freed. Basically it detects that destroy() method was called but cannot detect that counter is positive (it writes "Assuming condition is true" for counter zero check) in the stack trace. Is this possible to add some assert() so it understands that counter is positive here? Or may be it is really an incorrect shared pointer implementation?
c++ clang shared-ptr clang-static-analyzer
asked Nov 24 '18 at 8:40
Alexander BAlexander B
19213
Clang static analyzer reports a memory use after it's freed with a following implementation of the shared ptr (rather naive but still it should work fine):
template <class T>
class Shared
{
public:
Shared()
: ptr(0) , count(0)
{
}
explicit Shared(T* otherPtr)
: ptr(0), count(0)
{
init(otherPtr);
}
template <class DerivedT>
explicit Shared(DerivedT* otherPtr)
: ptr(0), count(0)
{
init(otherPtr);
}
explicit Shared(OutRef<T> ref)
: ptr(0), count(0)
{
init(ref.ptr);
}
Shared(const Shared& other)
: ptr(other.ptr), count(other.count)
{
addShared();
}
template <class DerivedT>
Shared(const Shared<DerivedT>& other)
: ptr(other.ptr), count(other.count)
{
addShared();
}
Shared& operator = (const Shared& other)
{
Shared tmp(other);
swap(tmp);
return *this;
}
template <class DerivedT>
Shared& operator = (const Shared<DerivedT>& other)
{
Shared tmp(other);
swap(tmp);
return *this;
}
~Shared()
{
destroy();
}
operator bool() const
{
return ptr != 0;
}
void operator = (T* otherPtr)
{
set(otherPtr);
}
template <class DerivedT>
void operator = (DerivedT* otherPtr)
{
set(otherPtr);
}
void operator = (OutRef<T> ref)
{
set(ref.ptr);
}
T* operator->()
{
return ptr;
}
const T* operator->() const
{
return ptr;
}
T& operator*()
{
return *ptr;
}
const T& operator*() const
{
return *ptr;
}
template <class DerivedT>
void set(DerivedT* otherPtr)
{
if (ptr != otherPtr)
{
destroy();
init(otherPtr);
}
}
T* get()
{
return ptr;
}
const T* get() const
{
return ptr;
}
operator T*()
{
return ptr;
}
operator const T*() const
{
return ptr;
}
template <class TT>
Shared<TT> cast()
{
Shared<TT> result;
result.ptr = (TT*)ptr;
result.count = count;
result.addShared();
return result;
}
bool isLastOwner() const
{
return count && *count == 1;
}
private:
void addShared()
{
if (count)
{
*count += 1;
}
}
template <class DerivedT>
void init(DerivedT* otherPtr)
{
presume(ptr == 0);
presume(count == 0);
if (otherPtr == 0)
{
return;
}
ptr = otherPtr;
count = new Index(1);
}
void destroy()
{
if (count)
{
*count -= 1;
if (*count == 0)
{
presume(sizeof(T) > 0); //will break compilation in case of undefined T
delete ptr;
delete count;
}
}
ptr = 0;
count = 0;
}
void swap(Shared& other)
{
Swap(ptr, other.ptr);
Swap(count, other.count);
}
private:
T* ptr;
Index* count;
template <class OtherT> friend class Shared;
};
For example, if I have function Shared f() and use it as
Shared<X> a = f();
a->callSomeMethod();
I get static analyzer warning that "a" is used after memory is freed. Basically it detects that destroy() method was called but cannot detect that counter is positive (it writes "Assuming condition is true" for counter zero check) in the stack trace. Is this possible to add some assert() so it understands that counter is positive here? Or may be it is really an incorrect shared pointer implementation?
c++ clang shared-ptr clang-static-analyzer
c++ clang shared-ptr clang-static-analyzer
asked Nov 24 '18 at 8:40
Alexander BAlexander B
19213
asked Nov 24 '18 at 8:40
Alexander BAlexander B
19213
edited Nov 24 '18 at 9:23
Alexander B
asked Nov 24 '18 at 8:40
Alexander BAlexander B
19213
asked Nov 24 '18 at 8:40
Alexander BAlexander B
19213
asked Nov 24 '18 at 8:40
Alexander BAlexander B
19213
19213
add a comment |
add a comment |
0
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