Identifying uninitialized pointer - c++

Question

Considering:
my class.h
class MyClass
{
Var* var;
public:
MyClass();
};
my class.cpp
MyClass::MyClass()
{
if(var) {};
}
Is there any compiler, or compiler flag, that will tell me I forgot to initialize var, Var* var = nullptr;?
I tried Microsoft (Visual Studio 2019) and MinGW compilers on Qt Creator (Qt 5.15.2), passing -Wall flag to the compiler and seen nothing telling me about that.
So the above was on Windows. And the following I tried on macOS:
class MyClass
{
int* var;
public:
MyClass();
};
MyClass::MyClass()
{
if(var) {}
}
int main()
{
MyClass a;
return 0;
}
While compiling with
g++ -Wuninitialized main.cpp -o main
and
clang++ -Wuninitialized main.cpp -o main
I see no warning, even with -Wall. Why?
g++ --version
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/4.2.1
Apple clang version 13.0.0 (clang-1300.0.29.30)
Target: x86_64-apple-darwin21.3.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
clang++ --version
Apple clang version 13.0.0 (clang-1300.0.29.30)
Target: x86_64-apple-darwin21.3.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

Answer 1

With Visual Studio and the Microsoft C++ compiler, I suggest compiling your code at warning level 4 (/W4).
If you are using the IDE, in Solution Explorer right click on your project and select Properties.
Then select C/C++ | General, and choose Warning Level 4, as shown below:
However, testing your case with VS2019, I got this warning message even at warning level 3:
Warning C26495 Variable 'MyClass::var' is uninitialized. Always
initialize a member variable (type.6).