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Compiler Warning (level 1) C4319

Error Message

'operator' : zero extending 'type' to 'type' of greater size

The result of the ~ operator is unsigned and then converted to a larger type.

In the following example, ~(a - 1) is evaluated as a 32-bit unsigned long expression and then converted to 64 bits by zero extension. This leads to pointer truncations.

// C4319.cpp
// compile with: /W1 /Wp64 /Tc
void* p;
unsigned long a;
typedef unsigned __int64 ULONG_PTR;

int main() {
  p = (void*)((ULONG_PTR)p & ~(a - 1)); // C4319 expected
}

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