The analyzer has detected a potential error: incorrect addition of a character constant to a string literal pointer.
This error usually occurs when the programmer tries to unite a string literal with a character.
Consider a simple example of incorrect code:
std::string S = "abcd" + 'x';
The programmer expected to get the "abcdx" string, but actually value 120 will be added to the pointer to the "abcd" string. This will surely lead to the string literal overrun. To prevent this bug you should avoid such arithmetic operations over string and character variables.
This is the correct code:
std::string S = std::string("abcd") + 'x';
According to Common Weakness Enumeration, potential errors found by using this diagnostic are classified as CWE-480.
You can look at examples of errors detected by the V643 diagnostic.