Issue #6042: lnotab-based tracing is very complicated and isn't documented very well. There were at least 3 comment blocks purporting to document co_lnotab, and none did a very good job. This patch unifies them into Objects/lnotab_notes.txt which tries to completely capture the current state of affairs. I also discovered that we've attached 2 layers of patches to the basic tracing scheme. The first layer avoids jumping to instructions that don't start a line, to avoid problems in if statements and while loops. The second layer discovered that jumps backward do need to trace at instructions that don't start a line, so it added extra lnotab entries for 'while' and 'for' loops, and added a special case for backward jumps within the same line. I replaced these patches by just treating forward and backward jumps differently.

/* 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));
}