+# ifdef USE_KERN_PROC_PATHNAME
+ size_t size = 0;
+ int mib[4];
+ mib[0] = CTL_KERN;
+ mib[1] = KERN_PROC;
+ mib[2] = KERN_PROC_PATHNAME;
+ mib[3] = -1;
+
+ if (sysctl(mib, 4, NULL, &size, NULL, 0) == 0
+ && size > 0 && size < MAXPATHLEN * MAXPATHLEN) {
+ sv_grow(caret_x, size);
+
+ if (sysctl(mib, 4, SvPVX(caret_x), &size, NULL, 0) == 0
+ && size > 2) {
+ SvPOK_only(caret_x);
+ SvCUR_set(caret_x, size - 1);
+ SvTAINT(caret_x);
+ return;
+ }
+ }
+# elif defined(USE_NSGETEXECUTABLEPATH)
+ char buf[1];
+ uint32_t size = sizeof(buf);
+ int result;
+
+ _NSGetExecutablePath(buf, &size);
+ if (size < MAXPATHLEN * MAXPATHLEN) {
+ sv_grow(caret_x, size);
+ if (_NSGetExecutablePath(SvPVX(caret_x), &size) == 0) {
+ char *const tidied = realpath(SvPVX(caret_x), NULL);
+ if (tidied) {
+ sv_setpv(caret_x, tidied);
+ free(tidied);
+ } else {
+ SvPOK_only(caret_x);
+ SvCUR_set(caret_x, size);
+ }
+ return;
+ }
+ }
+# elif defined(HAS_PROCSELFEXE)
+ char buf[MAXPATHLEN];
+ int len = readlink(PROCSELFEXE_PATH, buf, sizeof(buf) - 1);
+
+ /* On Playstation2 Linux V1.0 (kernel 2.2.1) readlink(/proc/self/exe)
+ includes a spurious NUL which will cause $^X to fail in system
+ or backticks (this will prevent extensions from being built and
+ many tests from working). readlink is not meant to add a NUL.
+ Normal readlink works fine.
+ */
+ if (len > 0 && buf[len-1] == '\0') {
+ len--;
+ }
+
+ /* FreeBSD's implementation is acknowledged to be imperfect, sometimes
+ returning the text "unknown" from the readlink rather than the path
+ to the executable (or returning an error from the readlink). Any
+ valid path has a '/' in it somewhere, so use that to validate the
+ result. See http://www.freebsd.org/cgi/query-pr.cgi?pr=35703
+ */
+ if (len > 0 && memchr(buf, '/', len)) {
+ sv_setpvn(caret_x, buf, len);
+ return;
+ }
+# endif
+ /* Fallback to this: */
+ sv_setpv(caret_x, PL_origargv[0]);