warning C6308: 'realloc' may return null pointer: assigning a null pointer to <variable>, which is passed as an argument to 'realloc', will cause the original memory block to be leaked
This warning indicates a memory leak that is the result of the incorrect use of a reallocation function. Heap reallocation functions do not free the passed buffer if reallocation is unsuccessful. To correct the defect, assign the result of the reallocation function to a temporary, and then replace the original pointer after successful reallocation.
Example
The following sample code generates this warning:
#include <malloc.h>
#include <windows.h>
void f( )
{
char *x;
x = (char *) malloc(10);
if (x != NULL)
{
x = (char *) realloc(x, 512);
// code...
free(x);
}
}
To correct this warning, use the following code:
#include <malloc.h>
#include <windows.h>
void f()
{
char *x, *tmp;
x = (char *) malloc(10);
if (x != NULL)
{
tmp = (char *) realloc(x,512);
if (tmp != NULL)
{
x = tmp;
}
free(x);
}
}
This warning might generate noise if there is a live alias to the buffer-to-be-reallocated at the time of the assignment of the result of the reallocation function.