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V121. Implicit conversion of the type o…


V121. Implicit conversion of the type of 'new' operator's argument to size_t type.

The analyzer detected a potential error related to calling the operator new. A value of a non-memsize type is passed to the operator "new" as an argument. The operator new takes values of the type size_t, and passing a 32-bit actual argument may signal a potential overflow that may occur when calculating the memory amount being allocated.

Here is an example: 

unsigned a = 5;
unsigned b = 1024;
unsigned c = 1024;
unsigned d = 1024;
char *ptr = new char[a*b*c*d]; //V121

Here you may see an overflow occurring when calculating the expression "a*b*c*d". As a result, the program allocates less memory than it should. To correct the code, use the type size_t:

size_t a = 5;
size_t b = 1024;
size_t c = 1024;
size_t d = 1024;
char *ptr = new char[a*b*c*d]; //Ok

The error will not be diagnosed if the value of the argument is defined as a safe 32-bit constant value. Here is an example of safe code:

char *ptr = new char[100]; 
const int size = 3*3;
char *p2 = new char[size];

This warning message is similar to the warning V106.

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