Provide a sanity check during PyThreadState_DeleteCurrent() and PyThreadState_Delete() to avoid an infinite loop when the tstate list is messed up and has somehow becomes circular and does not contain the current thread. I don't know how this happens but it does, *very* rarely. On more than one hardware platform. I have not been able to reproduce it manually. Attaching to a process where its happening: it has always been in an infinite loop over a single element tstate list that is not the tstate we're looking to delete. It has been in t_bootstrap()'s call to PyThreadState_DeleteCurrent() as a pthread is exiting.

/* Cross platform case insenstive 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(*s1) == tolower(*s2))) {
		if (!*s1++ || !*s2++)
			break;
	}
	return tolower(*s1) - tolower(*s2);
}

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