Make importlib compatible with __import__ by "fixing" code.co_filename paths. __import__ does a little trick when importing from bytecode by back-patching the co_filename paths to point to the file location where the code object was loaded from, *not* where the code object was originally created. This allows co_filename to point to a valid path. Problem is that co_filename is immutable from Python, so a private function -- imp._fix_co_filename() -- had to be introduced in order to get things working properly. Originally the plan was to add a file argument to marshal.loads(), but that failed as the algorithm used by __import__ is not fully recursive as one might expect, so to be fully backwards-compatible the code used by __import__ needed to be exposed. This closes issue #6811 by taking a different approach than outlined in the issue.

/* Cross platform case insensitive string compare functions
 */

#include "Python.h"

int
PyOS_mystrnicmp(const char *s1, const char *s2, Py_ssize_t size)
{
    if (size == 0)
        return 0;
    while ((--size > 0) &&
           (tolower((unsigned)*s1) == tolower((unsigned)*s2))) {
        if (!*s1++ || !*s2++)
            break;
    }
    return tolower((unsigned)*s1) - tolower((unsigned)*s2);
}

int
PyOS_mystricmp(const char *s1, const char *s2)
{
    while (*s1 && (tolower((unsigned)*s1++) == tolower((unsigned)*s2++))) {
        ;
    }
    return (tolower((unsigned)*s1) - tolower((unsigned)*s2));
}