Compiler Warning (level 1) C4311


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The latest version of this topic can be found at Compiler Warning (level 1) C4311.

variable' : pointer truncation from 'type' to 'type'

This warning detects 64-bit pointer truncation issues. For example, if code is compiled for a 64-bit architecture, the value of a pointer (64 bits) will be truncated if it is assigned to an int (32 bits). For more information, see Rules for Using Pointers.

For additional information about common causes of warning C4311, see Common Compiler Errors.

The following code example generates C4311 when compiled for a 64-bit target, and then demonstrates how to fix it:

// C4311.cpp  
// compile by using: cl /W1 C4311.cpp  
int main() {  
   void* p = &p;  
   unsigned int i = (unsigned int) p;   // C4311 for 64-bit targets  
   unsigned long long j = (unsigned long long) p;   // OK