CodeQL library for C/C++
codeql/cpp-all 1.1.0 (changelog, source)

Primitive predicate string::indexOf

Returns the index of the n’th (starting at 0) occurrence of the given string within the receiver, starting at the given 0-based offset. Has no result if the string does not occur in the receiver.

int indexOf(string substringToFind, int n, int startAt)