/*    caretx.c
 *
 *    Copyright (C) 2013
 *     by Larry Wall and others
 *
 *    You may distribute under the terms of either the GNU General Public
 *    License or the Artistic License, as specified in the README file.
 *
 */

/*
 *   'I do not know clearly,' said Frodo; 'but the path climbs, I think,
 * up into the mountains on the northern side of that vale where the old
 * city stands.  It goes up to a high cleft and so down to -- that which
 * is beyond.'
 *   'Do you know the name of that high pass?' said Faramir.
 *
 *     [p.691 of _The Lord of the Rings_, IV/xi: "The Forbidden Pool"]
 */

/* This file contains a single function, set_caret_X, to set the $^X
 * variable.  It's only used in perl.c, but has various OS dependencies,
 * so its been moved to its own file to reduce header pollution.
 * See RT 120314 for details.
 */

#if defined(PERL_IS_MINIPERL) && !defined(USE_SITECUSTOMIZE)
#  define USE_SITECUSTOMIZE
#endif

#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

#ifdef NETWARE
#include "nwutil.h"
#endif

#ifdef USE_KERN_PROC_PATHNAME
#  include <sys/sysctl.h>
#endif

#ifdef USE_NSGETEXECUTABLEPATH
# include <mach-o/dyld.h>
#endif

/* Note: Functions in this file must not have bool parameters.  When
   PERL_BOOL_AS_CHAR is #defined, mach-o/dyld.h overrides it in this file
   by #including stdbool.h, so the function parameters here would conflict
   with those in proto.h.
*/

void
Perl_set_caret_X(pTHX) {
    GV* tmpgv = gv_fetchpvs("\030", GV_ADD|GV_NOTQUAL, SVt_PV); /* $^X */
    if (tmpgv) {
        SV *const caret_x = GvSV(tmpgv);
#if defined(OS2)
        sv_setpv(caret_x, os2_execname(aTHX));
#else
#  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);

        _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];
        SSize_t len = readlink(PROCSELFEXE_PATH, buf, sizeof(buf) - 1);
        /* NOTE: if the length returned by readlink() is sizeof(buf) - 1,
         * it is impossible to know whether the result was truncated. */

        if (len != -1) {
            buf[len] = '\0';
        }

        /* 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]);
#endif
    }
}

/*
 * ex: set ts=8 sts=4 sw=4 et:
 */
