# V5004. OWASP. Consider inspecting the expression. Bit shifting of the 32-bit value with a subsequent expansion to the 64-bit type.

The analyzer has detected a potential error in an expression containing a shift operation: a 32-bit value is shifted in the program. The resulting 32-bit value is then explicitly or implicitly cast to a 64-bit type.

Consider an example of incorrect code:

    unsigned __int64 X;
    X = 1u << N;

This code causes undefined behavior if the N value is higher than 32. In practice, it means that you cannot use this code to write a value higher than 0x80000000 into the 'X' variable.

You can fix the code by making the type of the left argument 64-bit.

This is the correct code:

    unsigned __int64 X;
    X = 1ui64 << N;

The analyzer will not generate the warning if the result of an expression with the shift operation fits into a 32-bit type. It means that significant bits don't get lost and the code is correct.

This is an example of safe code:

    char W = 7;
    long long Q = W << 10;

The code works in the following way. At first, the 'W' variable is extended to the 32-bit 'int' type. Then a shift operation is performed and we get the value 0x00001C00. This number fits into a 32-bit type, which means that no error occurs. At the last step this value is extended to the 64-bit 'long long' type and written into the 'Q' variable.

This diagnostic is classified as:

CWE-190 OWASP-5.4.3 CERT-INT00-C

You can look at examples of errors detected by the V5004 diagnostic.