The analyzer detected a potential error in the program: coincidence of two actual arguments of a function. Passing the same value as two arguments is a normal thing for many functions. But if you deal with such functions as memmove, memcpy, strstr and strncmp, you must check the code.
Here is a sample from a real application:
#define str_cmp(s1, s2) wcscmp(s1, s2) ... v = abs(str_cmp(a->tdata, a->tdata));
The misprint here causes the wcscmp function to perform comparison of a string from itself. This is the correct code:
v = abs(str_cmp(a->tdata, b->tdata));
The analyzer generates the warning if the following functions are being handled: memcpy, memmove, memcmp, _memicmp, strstr, strspn, strtok, strcmp, strncmp, wcscmp, _stricmp, wcsncmp, etc. If you found a similar error that analyzer fails to diagnose, please tell us the name of the function that must not take same values as the first and second arguments.
According to Common Weakness Enumeration, potential errors found by using this diagnostic are classified as CWE-688.
You can look at examples of errors detected by the V549 diagnostic.