dln.c

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/**********************************************************************

  dln.c -

  $Author: eban $
  $Date: 2005/11/26 11:01:01 $
  created at: Tue Jan 18 17:05:06 JST 1994

  Copyright (C) 1993-2003 Yukihiro Matsumoto

**********************************************************************/

#include "ruby.h"
#include "dln.h"

#ifdef HAVE_STDLIB_H
# include <stdlib.h>
#endif

#ifdef __CHECKER__
#undef HAVE_DLOPEN
#undef USE_DLN_A_OUT
#undef USE_DLN_DLOPEN
#endif

#ifdef USE_DLN_A_OUT
char *dln_argv0;
#endif

#ifdef _AIX
#pragma alloca
#endif

#if defined(HAVE_ALLOCA_H)
#include <alloca.h>
#endif

#ifdef HAVE_STRING_H
# include <string.h>
#else
# include <strings.h>
#endif

#ifndef xmalloc
void *xmalloc();
void *xcalloc();
void *xrealloc();
#endif

#include <stdio.h>
#if defined(_WIN32) || defined(__VMS)
#include "missing/file.h"
#endif
#include <sys/types.h>
#include <sys/stat.h>

#ifndef S_ISDIR
#   define S_ISDIR(m) ((m & S_IFMT) == S_IFDIR)
#endif

#ifdef HAVE_SYS_PARAM_H
# include <sys/param.h>
#endif
#ifndef MAXPATHLEN
# define MAXPATHLEN 1024
#endif

#ifdef HAVE_UNISTD_H
# include <unistd.h>
#endif

#ifndef _WIN32
char *getenv();
#endif

#if defined(__VMS)
#pragma builtins
#include <dlfcn.h>
#endif

#ifdef __MACOS__
# include <TextUtils.h>
# include <CodeFragments.h>
# include <Aliases.h>
# include "macruby_private.h"
#endif

#ifdef __BEOS__
# include <image.h>
#endif

int eaccess();

#ifndef NO_DLN_LOAD

#if defined(HAVE_DLOPEN) && !defined(USE_DLN_A_OUT) && !defined(_AIX) && !defined(__APPLE__) && !defined(_UNICOSMP)
/* dynamic load with dlopen() */
# define USE_DLN_DLOPEN
#endif

#ifndef FUNCNAME_PATTERN
# if defined(__hp9000s300) ||  (defined(__NetBSD__) && !defined(__ELF__)) || defined(__BORLANDC__) || (defined(__FreeBSD__) && !defined(__ELF__)) || (defined(__OpenBSD__) && !defined(__ELF__)) || defined(NeXT) || defined(__WATCOMC__) || defined(__APPLE__)
#  define FUNCNAME_PATTERN "_Init_%s"
# else
#  define FUNCNAME_PATTERN "Init_%s"
# endif
#endif

static int
init_funcname_len(buf, file)
    char **buf;
    const char *file;
{
    char *p;
    const char *slash;
    int len;

    /* Load the file as an object one */
    for (slash = file-1; *file; file++) /* Find position of last '/' */
#ifdef __MACOS__
        if (*file == ':') slash = file;
#else
        if (*file == '/') slash = file;
#endif

    len = strlen(FUNCNAME_PATTERN) + strlen(slash + 1);
    *buf = xmalloc(len);
    snprintf(*buf, len, FUNCNAME_PATTERN, slash + 1);
    for (p = *buf; *p; p++) {         /* Delete suffix if it exists */
        if (*p == '.') {
            *p = '\0'; break;
        }
    }
    return p - *buf;
}

#define init_funcname(buf, file) do {\
    int len = init_funcname_len(buf, file);\
    char *tmp = ALLOCA_N(char, len+1);\
    if (!tmp) {\
        free(*buf);\
        rb_memerror();\
    }\
    strcpy(tmp, *buf);\
    free(*buf);\
    *buf = tmp;\
} while (0)

#ifdef USE_DLN_A_OUT

#ifndef LIBC_NAME
# define LIBC_NAME "libc.a"
#endif

#ifndef DLN_DEFAULT_LIB_PATH
#  define DLN_DEFAULT_LIB_PATH "/lib:/usr/lib:/usr/local/lib:."
#endif

#include <errno.h>

static int dln_errno;

#define DLN_ENOEXEC     ENOEXEC /* Exec format error */
#define DLN_ECONFL      1201    /* Symbol name conflict */
#define DLN_ENOINIT     1202    /* No initializer given */
#define DLN_EUNDEF      1203    /* Undefine symbol remains */
#define DLN_ENOTLIB     1204    /* Not a library file */
#define DLN_EBADLIB     1205    /* Malformed library file */
#define DLN_EINIT       1206    /* Not initialized */

static int dln_init_p = 0;

#include <ar.h>
#include <a.out.h>
#ifndef N_COMM
# define N_COMM 0x12
#endif
#ifndef N_MAGIC
# define N_MAGIC(x) (x).a_magic
#endif

#define INVALID_OBJECT(h) (N_MAGIC(h) != OMAGIC)

#include "util.h"
#include "st.h"

static st_table *sym_tbl;
static st_table *undef_tbl;

static int load_lib();

static int
load_header(fd, hdrp, disp)
    int fd;
    struct exec *hdrp;
    long disp;
{
    int size;

    lseek(fd, disp, 0);
    size = read(fd, hdrp, sizeof(struct exec));
    if (size == -1) {
        dln_errno = errno;
        return -1;
    }
    if (size != sizeof(struct exec) || N_BADMAG(*hdrp)) {
        dln_errno = DLN_ENOEXEC;
        return -1;
    }
    return 0;
}

#if defined(sequent)
#define RELOC_SYMBOL(r)                 ((r)->r_symbolnum)
#define RELOC_MEMORY_SUB_P(r)           ((r)->r_bsr)
#define RELOC_PCREL_P(r)                ((r)->r_pcrel || (r)->r_bsr)
#define RELOC_TARGET_SIZE(r)            ((r)->r_length)
#endif

/* Default macros */
#ifndef RELOC_ADDRESS
#define RELOC_ADDRESS(r)                ((r)->r_address)
#define RELOC_EXTERN_P(r)               ((r)->r_extern)
#define RELOC_SYMBOL(r)                 ((r)->r_symbolnum)
#define RELOC_MEMORY_SUB_P(r)           0
#define RELOC_PCREL_P(r)                ((r)->r_pcrel)
#define RELOC_TARGET_SIZE(r)            ((r)->r_length)
#endif

#if defined(sun) && defined(sparc)
/* Sparc (Sun 4) macros */
#  undef relocation_info
#  define relocation_info reloc_info_sparc
#  define R_RIGHTSHIFT(r)       (reloc_r_rightshift[(r)->r_type])
#  define R_BITSIZE(r)          (reloc_r_bitsize[(r)->r_type])
#  define R_LENGTH(r)           (reloc_r_length[(r)->r_type])
static int reloc_r_rightshift[] = {
  0, 0, 0, 0, 0, 0, 2, 2, 10, 0, 0, 0, 0, 0, 0,
};
static int reloc_r_bitsize[] = {
  8, 16, 32, 8, 16, 32, 30, 22, 22, 22, 13, 10, 32, 32, 16,
};
static int reloc_r_length[] = {
  0, 1, 2, 0, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
};
#  define R_PCREL(r) \
    ((r)->r_type >= RELOC_DISP8 && (r)->r_type <= RELOC_WDISP22)
#  define R_SYMBOL(r) ((r)->r_index)
#endif

#if defined(sequent)
#define R_SYMBOL(r)             ((r)->r_symbolnum)
#define R_MEMORY_SUB(r)         ((r)->r_bsr)
#define R_PCREL(r)              ((r)->r_pcrel || (r)->r_bsr)
#define R_LENGTH(r)             ((r)->r_length)
#endif

#ifndef R_SYMBOL
#  define R_SYMBOL(r)           ((r)->r_symbolnum)
#  define R_MEMORY_SUB(r)       0
#  define R_PCREL(r)            ((r)->r_pcrel)
#  define R_LENGTH(r)           ((r)->r_length)
#endif

static struct relocation_info *
load_reloc(fd, hdrp, disp)
     int fd;
     struct exec *hdrp;
     long disp;
{
    struct relocation_info *reloc;
    int size;

    lseek(fd, disp + N_TXTOFF(*hdrp) + hdrp->a_text + hdrp->a_data, 0);
    size = hdrp->a_trsize + hdrp->a_drsize;
    reloc = (struct relocation_info*)xmalloc(size);
    if (reloc == NULL) {
        dln_errno = errno;
        return NULL;
    }

    if (read(fd, reloc, size) !=  size) {
        dln_errno = errno;
        free(reloc);
        return NULL;
    }

    return reloc;
}

static struct nlist *
load_sym(fd, hdrp, disp)
    int fd;
    struct exec *hdrp;
    long disp;
{
    struct nlist * buffer;
    struct nlist * sym;
    struct nlist * end;
    long displ;
    int size;

    lseek(fd, N_SYMOFF(*hdrp) + hdrp->a_syms + disp, 0);
    if (read(fd, &size, sizeof(int)) != sizeof(int)) {
        goto err_noexec;
    }

    buffer = (struct nlist*)xmalloc(hdrp->a_syms + size);
    if (buffer == NULL) {
        dln_errno = errno;
        return NULL;
    }

    lseek(fd, disp + N_SYMOFF(*hdrp), 0);
    if (read(fd, buffer, hdrp->a_syms + size) != hdrp->a_syms + size) {
        free(buffer);
        goto err_noexec;
    }

    sym = buffer;
    end = sym + hdrp->a_syms / sizeof(struct nlist);
    displ = (long)buffer + (long)(hdrp->a_syms);

    while (sym < end) {
        sym->n_un.n_name = (char*)sym->n_un.n_strx + displ;
        sym++;
    }
    return buffer;

  err_noexec:
    dln_errno = DLN_ENOEXEC;
    return NULL;
}

static st_table *
sym_hash(hdrp, syms)
    struct exec *hdrp;
    struct nlist *syms;
{
    st_table *tbl;
    struct nlist *sym = syms;
    struct nlist *end = syms + (hdrp->a_syms / sizeof(struct nlist));

    tbl = st_init_strtable();
    if (tbl == NULL) {
        dln_errno = errno;
        return NULL;
    }

    while (sym < end) {
        st_insert(tbl, sym->n_un.n_name, sym);
        sym++;
    }
    return tbl;
}

static int
dln_init(prog)
    const char *prog;
{
    char *file;
    int fd;
    struct exec hdr;
    struct nlist *syms;

    if (dln_init_p == 1) return 0;

    file = dln_find_exe(prog, NULL);
    if (file == NULL || (fd = open(file, O_RDONLY)) < 0) {
        dln_errno = errno;
        return -1;
    }

    if (load_header(fd, &hdr, 0) == -1) return -1;
    syms = load_sym(fd, &hdr, 0);
    if (syms == NULL) {
        close(fd);
        return -1;
    }
    sym_tbl = sym_hash(&hdr, syms);
    if (sym_tbl == NULL) {      /* file may be start with #! */
        char c = '\0';
        char buf[MAXPATHLEN];
        char *p;

        free(syms);
        lseek(fd, 0L, 0);
        if (read(fd, &c, 1) == -1) {
            dln_errno = errno;
            return -1;
        }
        if (c != '#') goto err_noexec;
        if (read(fd, &c, 1) == -1) {
            dln_errno = errno;
            return -1;
        }
        if (c != '!') goto err_noexec;

        p = buf;
        /* skip forwarding spaces */
        while (read(fd, &c, 1) == 1) {
            if (c == '\n') goto err_noexec;
            if (c != '\t' && c != ' ') {
                *p++ = c;
                break;
            }
        }
        /* read in command name */
        while (read(fd, p, 1) == 1) {
            if (*p == '\n' || *p == '\t' || *p == ' ') break;
            p++;
            if (p-buf >= MAXPATHLEN) {
                dln_errno = ENAMETOOLONG;
                return -1;
            }
        }
        *p = '\0';

        return dln_init(buf);
    }
    dln_init_p = 1;
    undef_tbl = st_init_strtable();
    close(fd);
    return 0;

  err_noexec:
    close(fd);
    dln_errno = DLN_ENOEXEC;
    return -1;
}

static long
load_text_data(fd, hdrp, bss, disp)
    int fd;
    struct exec *hdrp;
    int bss;
    long disp;
{
    int size;
    unsigned char* addr;

    lseek(fd, disp + N_TXTOFF(*hdrp), 0);
    size = hdrp->a_text + hdrp->a_data;

    if (bss == -1) size += hdrp->a_bss;
    else if (bss > 1) size += bss;

    addr = (unsigned char*)xmalloc(size);
    if (addr == NULL) {
        dln_errno = errno;
        return 0;
    }

    if (read(fd, addr, size) !=  size) {
        dln_errno = errno;
        free(addr);
        return 0;
    }

    if (bss == -1) {
        memset(addr +  hdrp->a_text + hdrp->a_data, 0, hdrp->a_bss);
    }
    else if (bss > 0) {
        memset(addr +  hdrp->a_text + hdrp->a_data, 0, bss);
    }

    return (long)addr;
}

static int
undef_print(key, value)
    char *key, *value;
{
    fprintf(stderr, "  %s\n", key);
    return ST_CONTINUE;
}

static void
dln_print_undef()
{
    fprintf(stderr, " Undefined symbols:\n");
    st_foreach(undef_tbl, undef_print, NULL);
}

static void
dln_undefined()
{
    if (undef_tbl->num_entries > 0) {
        fprintf(stderr, "dln: Calling undefined function\n");
        dln_print_undef();
        rb_exit(1);
    }
}

struct undef {
    char *name;
    struct relocation_info reloc;
    long base;
    char *addr;
    union {
        char c;
        short s;
        long l;
    } u;
};

static st_table *reloc_tbl = NULL;
static void
link_undef(name, base, reloc)
    const char *name;
    long base;
    struct relocation_info *reloc;
{
    static int u_no = 0;
    struct undef *obj;
    char *addr = (char*)(reloc->r_address + base);

    obj = (struct undef*)xmalloc(sizeof(struct undef));
    obj->name = strdup(name);
    obj->reloc = *reloc;
    obj->base = base;
    switch (R_LENGTH(reloc)) {
      case 0:           /* byte */
        obj->u.c = *addr;
        break;
      case 1:           /* word */
        obj->u.s = *(short*)addr;
        break;
      case 2:           /* long */
        obj->u.l = *(long*)addr;
        break;
    }
    if (reloc_tbl == NULL) {
        reloc_tbl = st_init_numtable();
    }
    st_insert(reloc_tbl, u_no++, obj);
}

struct reloc_arg {
    const char *name;
    long value;
};

static int
reloc_undef(no, undef, arg)
    int no;
    struct undef *undef;
    struct reloc_arg *arg;
{
    int datum;
    char *address;
#if defined(sun) && defined(sparc)
    unsigned int mask = 0;
#endif

    if (strcmp(arg->name, undef->name) != 0) return ST_CONTINUE;
    address = (char*)(undef->base + undef->reloc.r_address);
    datum = arg->value;

    if (R_PCREL(&(undef->reloc))) datum -= undef->base;
#if defined(sun) && defined(sparc)
    datum += undef->reloc.r_addend;
    datum >>= R_RIGHTSHIFT(&(undef->reloc));
    mask = (1 << R_BITSIZE(&(undef->reloc))) - 1;
    mask |= mask -1;
    datum &= mask;
    switch (R_LENGTH(&(undef->reloc))) {
      case 0:
        *address = undef->u.c;
        *address &= ~mask;
        *address |= datum;
        break;
      case 1:
        *(short *)address = undef->u.s;
        *(short *)address &= ~mask;
        *(short *)address |= datum;
        break;
      case 2:
        *(long *)address = undef->u.l;
        *(long *)address &= ~mask;
        *(long *)address |= datum;
        break;
    }
#else
    switch (R_LENGTH(&(undef->reloc))) {
      case 0:           /* byte */
        if (R_MEMORY_SUB(&(undef->reloc)))
            *address = datum - *address;
        else *address = undef->u.c + datum;
        break;
      case 1:           /* word */
        if (R_MEMORY_SUB(&(undef->reloc)))
            *(short*)address = datum - *(short*)address;
        else *(short*)address = undef->u.s + datum;
        break;
      case 2:           /* long */
        if (R_MEMORY_SUB(&(undef->reloc)))
            *(long*)address = datum - *(long*)address;
        else *(long*)address = undef->u.l + datum;
        break;
    }
#endif
    free(undef->name);
    free(undef);
    return ST_DELETE;
}

static void
unlink_undef(name, value)
    const char *name;
    long value;
{
    struct reloc_arg arg;

    arg.name = name;
    arg.value = value;
    st_foreach(reloc_tbl, reloc_undef, &arg);
}

#ifdef N_INDR
struct indr_data {
    char *name0, *name1;
};

static int
reloc_repl(no, undef, data)
    int no;
    struct undef *undef;
    struct indr_data *data;
{
    if (strcmp(data->name0, undef->name) == 0) {
        free(undef->name);
        undef->name = strdup(data->name1);
    }
    return ST_CONTINUE;
}
#endif

static int
load_1(fd, disp, need_init)
    int fd;
    long disp;
    const char *need_init;
{
    static char *libc = LIBC_NAME;
    struct exec hdr;
    struct relocation_info *reloc = NULL;
    long block = 0;
    long new_common = 0; /* Length of new common */
    struct nlist *syms = NULL;
    struct nlist *sym;
    struct nlist *end;
    int init_p = 0;

    if (load_header(fd, &hdr, disp) == -1) return -1;
    if (INVALID_OBJECT(hdr)) {
        dln_errno = DLN_ENOEXEC;
        return -1;
    }
    reloc = load_reloc(fd, &hdr, disp);
    if (reloc == NULL) return -1;

    syms = load_sym(fd, &hdr, disp);
    if (syms == NULL) {
        free(reloc);
        return -1;
    }

    sym = syms;
    end = syms + (hdr.a_syms / sizeof(struct nlist));
    while (sym < end) {
        struct nlist *old_sym;
        int value = sym->n_value;

#ifdef N_INDR
        if (sym->n_type == (N_INDR | N_EXT)) {
            char *key = sym->n_un.n_name;

            if (st_lookup(sym_tbl, sym[1].n_un.n_name, &old_sym)) {
                if (st_delete(undef_tbl, (st_data_t*)&key, NULL)) {
                    unlink_undef(key, old_sym->n_value);
                    free(key);
                }
            }
            else {
                struct indr_data data;

                data.name0 = sym->n_un.n_name;
                data.name1 = sym[1].n_un.n_name;
                st_foreach(reloc_tbl, reloc_repl, &data);

                st_insert(undef_tbl, strdup(sym[1].n_un.n_name), NULL);
                if (st_delete(undef_tbl, (st_data_t*)&key, NULL)) {
                    free(key);
                }
            }
            sym += 2;
            continue;
        }
#endif
        if (sym->n_type == (N_UNDF | N_EXT)) {
            if (st_lookup(sym_tbl, sym->n_un.n_name, &old_sym) == 0) {
                old_sym = NULL;
            }

            if (value) {
                if (old_sym) {
                    sym->n_type = N_EXT | N_COMM;
                    sym->n_value = old_sym->n_value;
                }
                else {
                    int rnd =
                        value >= sizeof(double) ? sizeof(double) - 1
                            : value >= sizeof(long) ? sizeof(long) - 1
                                : sizeof(short) - 1;

                    sym->n_type = N_COMM;
                    new_common += rnd;
                    new_common &= ~(long)rnd;
                    sym->n_value = new_common;
                    new_common += value;
                }
            }
            else {
                if (old_sym) {
                    sym->n_type = N_EXT | N_COMM;
                    sym->n_value = old_sym->n_value;
                }
                else {
                    sym->n_value = (long)dln_undefined;
                    st_insert(undef_tbl, strdup(sym->n_un.n_name), NULL);
                }
            }
        }
        sym++;
    }

    block = load_text_data(fd, &hdr, hdr.a_bss + new_common, disp);
    if (block == 0) goto err_exit;

    sym = syms;
    while (sym < end) {
        struct nlist *new_sym;
        char *key;

        switch (sym->n_type) {
          case N_COMM:
            sym->n_value += hdr.a_text + hdr.a_data;
          case N_TEXT|N_EXT:
          case N_DATA|N_EXT:

            sym->n_value += block;

            if (st_lookup(sym_tbl, sym->n_un.n_name, &new_sym) != 0
                && new_sym->n_value != (long)dln_undefined) {
                dln_errno = DLN_ECONFL;
                goto err_exit;
            }

            key = sym->n_un.n_name;
            if (st_delete(undef_tbl, (st_data_t*)&key, NULL) != 0) {
                unlink_undef(key, sym->n_value);
                free(key);
            }

            new_sym = (struct nlist*)xmalloc(sizeof(struct nlist));
            *new_sym = *sym;
            new_sym->n_un.n_name = strdup(sym->n_un.n_name);
            st_insert(sym_tbl, new_sym->n_un.n_name, new_sym);
            break;

          case N_TEXT:
          case N_DATA:
            sym->n_value += block;
            break;
        }
        sym++;
    }

    /*
     * First comes the text-relocation
     */
    {
        struct relocation_info * rel = reloc;
        struct relocation_info * rel_beg = reloc +
            (hdr.a_trsize/sizeof(struct relocation_info));
        struct relocation_info * rel_end = reloc +
            (hdr.a_trsize+hdr.a_drsize)/sizeof(struct relocation_info);

        while (rel < rel_end) {
            char *address = (char*)(rel->r_address + block);
            long datum = 0;
#if defined(sun) && defined(sparc)
            unsigned int mask = 0;
#endif

            if(rel >= rel_beg)
                address += hdr.a_text;

            if (rel->r_extern) { /* Look it up in symbol-table */
                sym = &(syms[R_SYMBOL(rel)]);
                switch (sym->n_type) {
                  case N_EXT|N_UNDF:
                    link_undef(sym->n_un.n_name, block, rel);
                  case N_EXT|N_COMM:
                  case N_COMM:
                    datum = sym->n_value;
                    break;
                  default:
                    goto err_exit;
                }
            } /* end.. look it up */
            else { /* is static */
                switch (R_SYMBOL(rel)) { 
                  case N_TEXT:
                  case N_DATA:
                    datum = block;
                    break;
                  case N_BSS:
                    datum = block +  new_common;
                    break;
                  case N_ABS:
                    break;
                }
            } /* end .. is static */
            if (R_PCREL(rel)) datum -= block;

#if defined(sun) && defined(sparc)
            datum += rel->r_addend;
            datum >>= R_RIGHTSHIFT(rel);
            mask = (1 << R_BITSIZE(rel)) - 1;
            mask |= mask -1;
            datum &= mask;

            switch (R_LENGTH(rel)) {
              case 0:
                *address &= ~mask;
                *address |= datum;
                break;
              case 1:
                *(short *)address &= ~mask;
                *(short *)address |= datum;
                break;
              case 2:
                *(long *)address &= ~mask;
                *(long *)address |= datum;
                break;
            }
#else
            switch (R_LENGTH(rel)) {
              case 0:           /* byte */
                if (datum < -128 || datum > 127) goto err_exit;
                *address += datum;
                break;
              case 1:           /* word */
                *(short *)address += datum;
                break;
              case 2:           /* long */
                *(long *)address += datum;
                break;
            }
#endif
            rel++;
        }
    }

    if (need_init) {
        int len;
        char **libs_to_be_linked = 0;
        char *buf;

        if (undef_tbl->num_entries > 0) {
            if (load_lib(libc) == -1) goto err_exit;
        }

        init_funcname(&buf, need_init);
        len = strlen(buf);

        for (sym = syms; sym<end; sym++) {
            char *name = sym->n_un.n_name;
            if (name[0] == '_' && sym->n_value >= block) {
                if (strcmp(name+1, "dln_libs_to_be_linked") == 0) {
                    libs_to_be_linked = (char**)sym->n_value;
                }
                else if (strcmp(name+1, buf) == 0) {
                    init_p = 1;
                    ((int (*)())sym->n_value)();
                }
            }
        }
        if (libs_to_be_linked && undef_tbl->num_entries > 0) {
            while (*libs_to_be_linked) {
                load_lib(*libs_to_be_linked);
                libs_to_be_linked++;
            }
        }
    }
    free(reloc);
    free(syms);
    if (need_init) {
        if (init_p == 0) {
            dln_errno = DLN_ENOINIT;
            return -1;
        }
        if (undef_tbl->num_entries > 0) {
            if (load_lib(libc) == -1) goto err_exit;
            if (undef_tbl->num_entries > 0) {
                dln_errno = DLN_EUNDEF;
                return -1;
            }
        }
    }
    return 0;

  err_exit:
    if (syms) free(syms);
    if (reloc) free(reloc);
    if (block) free((char*)block);
    return -1;
}

static int target_offset;
static int
search_undef(key, value, lib_tbl)
    const char *key;
    int value;
    st_table *lib_tbl;
{
    long offset;

    if (st_lookup(lib_tbl, key, &offset) == 0) return ST_CONTINUE;
    target_offset = offset;
    return ST_STOP;
}

struct symdef {
    int rb_str_index;
    int lib_offset;
};

char *dln_librrb_ary_path = DLN_DEFAULT_LIB_PATH;

static int
load_lib(lib)
    const char *lib;
{
    char *path, *file;
    char armagic[SARMAG];
    int fd, size;
    struct ar_hdr ahdr;
    st_table *lib_tbl = NULL;
    int *data, nsym;
    struct symdef *base;
    char *name_base;

    if (dln_init_p == 0) {
        dln_errno = DLN_ENOINIT;
        return -1;
    }

    if (undef_tbl->num_entries == 0) return 0;
    dln_errno = DLN_EBADLIB;

    if (lib[0] == '-' && lib[1] == 'l') {
        long len = strlen(lib) + 4;
        char *p = alloca(len);
        snprintf(p, len, "lib%s.a", lib+2);
        lib = p;
    }

    /* library search path: */
    /* look for environment variable DLN_LIBRARY_PATH first. */
    /* then variable dln_librrb_ary_path. */
    /* if path is still NULL, use "." for path. */
    path = getenv("DLN_LIBRARY_PATH");
    if (path == NULL) path = dln_librrb_ary_path;

    file = dln_find_file(lib, path);
    fd = open(file, O_RDONLY);
    if (fd == -1) goto syserr;
    size = read(fd, armagic, SARMAG);
    if (size == -1) goto syserr;

    if (size != SARMAG) {
        dln_errno = DLN_ENOTLIB;
        goto badlib;
    }
    size = read(fd, &ahdr, sizeof(ahdr));
    if (size == -1) goto syserr;
    if (size != sizeof(ahdr) || sscanf(ahdr.ar_size, "%d", &size) != 1) {
        goto badlib;
    }

    if (strncmp(ahdr.ar_name, "__.SYMDEF", 9) == 0) {
        /* make hash table from __.SYMDEF */

        lib_tbl = st_init_strtable();
        data = (int*)xmalloc(size);
        if (data == NULL) goto syserr;
        size = read(fd, data, size);
        nsym = *data / sizeof(struct symdef);
        base = (struct symdef*)(data + 1);
        name_base = (char*)(base + nsym) + sizeof(int);
        while (nsym > 0) {
            char *name = name_base + base->rb_str_index;

            st_insert(lib_tbl, name, base->lib_offset + sizeof(ahdr));
            nsym--;
            base++;
        }
        for (;;) {
            target_offset = -1;
            st_foreach(undef_tbl, search_undef, lib_tbl);
            if (target_offset == -1) break;
            if (load_1(fd, target_offset, 0) == -1) {
                st_free_table(lib_tbl);
                free(data);
                goto badlib;
            }
            if (undef_tbl->num_entries == 0) break;
        }
        free(data);
        st_free_table(lib_tbl);
    }
    else {
        /* linear library, need to scan (FUTURE) */

        for (;;) {
            int offset = SARMAG;
            int found = 0;
            struct exec hdr;
            struct nlist *syms, *sym, *end;

            while (undef_tbl->num_entries > 0) {
                found = 0;
                lseek(fd, offset, 0);
                size = read(fd, &ahdr, sizeof(ahdr));
                if (size == -1) goto syserr;
                if (size == 0) break;
                if (size != sizeof(ahdr)
                    || sscanf(ahdr.ar_size, "%d", &size) != 1) {
                    goto badlib;
                }
                offset += sizeof(ahdr);
                if (load_header(fd, &hdr, offset) == -1)
                    goto badlib;
                syms = load_sym(fd, &hdr, offset);
                if (syms == NULL) goto badlib;
                sym = syms;
                end = syms + (hdr.a_syms / sizeof(struct nlist));
                while (sym < end) {
                    if (sym->n_type == N_EXT|N_TEXT
                        && st_lookup(undef_tbl, sym->n_un.n_name, NULL)) {
                        break;
                    }
                    sym++;
                }
                if (sym < end) {
                    found++;
                    free(syms);
                    if (load_1(fd, offset, 0) == -1) {
                        goto badlib;
                    }
                }
                offset += size;
                if (offset & 1) offset++;
            }
            if (found) break;
        }
    }
    close(fd);
    return 0;

  syserr:
    dln_errno = errno;
  badlib:
    if (fd >= 0) close(fd);
    return -1;
}

static int
load(file)
    const char *file;
{
    int fd;
    int result;

    if (dln_init_p == 0) {
        if (dln_init(dln_argv0) == -1) return -1;
    }
    result = strlen(file);
    if (file[result-1] == 'a') {
        return load_lib(file);
    }

    fd = open(file, O_RDONLY);
    if (fd == -1) {
        dln_errno = errno;
        return -1;
    }
    result = load_1(fd, 0, file);
    close(fd);

    return result;
}

void*
dln_sym(name)
    const char *name;
{
    struct nlist *sym;

    if (st_lookup(sym_tbl, name, &sym))
        return (void*)sym->n_value;
    return NULL;
}

#endif /* USE_DLN_A_OUT */

#ifdef USE_DLN_DLOPEN
# if defined(__NetBSD__) && defined(__NetBSD_Version__) && __NetBSD_Version__ < 105000000
#  include <nlist.h>
#  include <link.h>
# else
#  include <dlfcn.h>
# endif
#endif

#ifdef __hpux
#include <errno.h>
#include "dl.h"
#endif

#if defined(_AIX)
#include <ctype.h>      /* for isdigit()        */
#include <errno.h>      /* for global errno     */
#include <sys/ldr.h>
#endif

#ifdef NeXT
#if NS_TARGET_MAJOR < 4
#include <mach-o/rld.h>
#else
#include <mach-o/dyld.h>
#ifndef NSLINKMODULE_OPTION_BINDNOW
#define NSLINKMODULE_OPTION_BINDNOW 1
#endif
#endif
#else
#ifdef __APPLE__
#include <mach-o/dyld.h>
#endif
#endif

#if defined _WIN32 && !defined __CYGWIN__
#include <windows.h>
#endif

#ifdef _WIN32_WCE
#undef FormatMessage
#define FormatMessage FormatMessageA
#undef LoadLibrary
#define LoadLibrary LoadLibraryA
#undef GetProcAddress
#define GetProcAddress GetProcAddressA
#endif

static const char *
dln_strerror()
{
#ifdef USE_DLN_A_OUT
    char *strerror();

    switch (dln_errno) {
      case DLN_ECONFL:
        return "Symbol name conflict";
      case DLN_ENOINIT:
        return "No initializer given";
      case DLN_EUNDEF:
        return "Unresolved symbols";
      case DLN_ENOTLIB:
        return "Not a library file";
      case DLN_EBADLIB:
        return "Malformed library file";
      case DLN_EINIT:
        return "Not initialized";
      default:
        return strerror(dln_errno);
    }
#endif

#ifdef USE_DLN_DLOPEN
    return (char*)dlerror();
#endif

#if defined _WIN32 && !defined __CYGWIN__
    static char message[1024];
    int error = GetLastError();
    char *p = message;
    p += sprintf(message, "%d: ", error);
    FormatMessage(
        FORMAT_MESSAGE_FROM_SYSTEM       | FORMAT_MESSAGE_IGNORE_INSERTS,
        NULL,
        error,
        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
        p,
        sizeof message - strlen(message),
        NULL);

    for (p = message; *p; p++) {
        if (*p == '\n' || *p == '\r')
            *p = ' ';
    }
    return message;
#endif
}


#if defined(_AIX) && ! defined(_IA64)
static void
aix_loaderror(const char *pathname)
{
    char *message[8], errbuf[1024];
    int i,j;

    struct errtab { 
        int errnum;
        char *errstr;
    } load_errtab[] = {
        {L_ERROR_TOOMANY,       "too many errors, rest skipped."},
        {L_ERROR_NOLIB,         "can't load library:"},
        {L_ERROR_UNDEF,         "can't find symbol in library:"},
        {L_ERROR_RLDBAD,
             "RLD index out of range or bad relocation type:"},
        {L_ERROR_FORMAT,        "not a valid, executable xcoff file:"},
        {L_ERROR_MEMBER,
             "file not an archive or does not contain requested member:"},
        {L_ERROR_TYPE,          "symbol table mismatch:"},
        {L_ERROR_ALIGN,         "text alignment in file is wrong."},
        {L_ERROR_SYSTEM,        "System error:"},
        {L_ERROR_ERRNO,         NULL}
    };

#define LOAD_ERRTAB_LEN (sizeof(load_errtab)/sizeof(load_errtab[0]))
#define ERRBUF_APPEND(s) strncat(errbuf, s, sizeof(errbuf)-strlen(errbuf)-1)

    snprintf(errbuf, 1024, "load failed - %s ", pathname);

    if (!loadquery(1, &message[0], sizeof(message))) 
        ERRBUF_APPEND(strerror(errno));
    for(i = 0; message[i] && *message[i]; i++) {
        int nerr = atoi(message[i]);
        for (j=0; j<LOAD_ERRTAB_LEN; j++) {
           if (nerr == load_errtab[i].errnum && load_errtab[i].errstr)
                ERRBUF_APPEND(load_errtab[i].errstr);
        }
        while (isdigit(*message[i])) message[i]++; 
        ERRBUF_APPEND(message[i]);
        ERRBUF_APPEND("\n");
    }
    errbuf[strlen(errbuf)-1] = '\0';    /* trim off last newline */
    rb_loaderror(errbuf);
    return;
}
#endif

#if defined(__VMS)
#include <starlet.h>
#include <rms.h>
#include <stsdef.h>
#include <unixlib.h>
#include <descrip.h>
#include <lib$routines.h>

static char *vms_filespec;
static int vms_fileact(char *filespec, int type);
static long vms_fisexh(long *sigarr, long *mecarr);
#endif

#endif /* NO_DLN_LOAD */

void*
dln_load(file)
    const char *file;
{
#ifdef NO_DLN_LOAD
    rb_raise(rb_eLoadError, "this executable file can't load extension libraries");
#else

#if !defined(_AIX) && !defined(NeXT)
    const char *error = 0;
#define DLN_ERROR() (error = dln_strerror(), strcpy(ALLOCA_N(char, strlen(error) + 1), error))
#endif

#if defined _WIN32 && !defined __CYGWIN__
    HINSTANCE handle;
    char winfile[MAXPATHLEN];
    void (*init_fct)();
    char *buf;

    if (strlen(file) >= MAXPATHLEN) rb_loaderror("filename too long");

    /* Load the file as an object one */
    init_funcname(&buf, file);

    strcpy(winfile, file);

    /* Load file */
    if ((handle = LoadLibrary(winfile)) == NULL) {
        error = dln_strerror();
        goto failed;
    }

    if ((init_fct = (void(*)())GetProcAddress(handle, buf)) == NULL) {
        rb_loaderror("%s - %s\n%s", dln_strerror(), buf, file);
    }

    /* Call the init code */
    (*init_fct)();
    return handle;
#else
#ifdef USE_DLN_A_OUT
    if (load(file) == -1) {
        error = dln_strerror();
        goto failed;
    }
    return 0;
#else

    char *buf;
    /* Load the file as an object one */
    init_funcname(&buf, file);

#ifdef USE_DLN_DLOPEN
#define DLN_DEFINED
    {
        void *handle;
        void (*init_fct)();

#ifndef RTLD_LAZY
# define RTLD_LAZY 1
#endif
#ifdef __INTERIX
# undef RTLD_GLOBAL
#endif
#ifndef RTLD_GLOBAL
# define RTLD_GLOBAL 0
#endif

        /* Load file */
        if ((handle = (void*)dlopen(file, RTLD_LAZY|RTLD_GLOBAL)) == NULL) {
            error = dln_strerror();
            goto failed;
        }

        init_fct = (void(*)())dlsym(handle, buf);
        if (init_fct == NULL) {
            error = DLN_ERROR();
            dlclose(handle);
            goto failed;
        }
        /* Call the init code */
        (*init_fct)();

        return handle;
    }
#endif /* USE_DLN_DLOPEN */

#ifdef __hpux
#define DLN_DEFINED
    {
        shl_t lib = NULL;
        int flags;
        void (*init_fct)();

        flags = BIND_DEFERRED;
        lib = shl_load(file, flags, 0);
        if (lib == NULL) {
            extern int errno;
            rb_loaderror("%s - %s", strerror(errno), file);
        }
        shl_findsym(&lib, buf, TYPE_PROCEDURE, (void*)&init_fct);
        if (init_fct == NULL) {
            shl_findsym(&lib, buf, TYPE_UNDEFINED, (void*)&init_fct);
            if (init_fct == NULL) {
                errno = ENOSYM;
                rb_loaderror("%s - %s", strerror(ENOSYM), file);
            }
        }
        (*init_fct)();
        return (void*)lib;
    }
#endif /* hpux */

#if defined(_AIX) && ! defined(_IA64)
#define DLN_DEFINED
    {
        void (*init_fct)();

        init_fct = (void(*)())load((char*)file, 1, 0);
        if (init_fct == NULL) {
            aix_loaderror(file);
        }
        if (loadbind(0, (void*)dln_load, (void*)init_fct) == -1) {
            aix_loaderror(file);
        }
        (*init_fct)();
        return (void*)init_fct;
    }
#endif /* _AIX */

#if defined(NeXT) || defined(__APPLE__)
#define DLN_DEFINED
/*----------------------------------------------------
   By SHIROYAMA Takayuki Psi@fortune.nest.or.jp
 
   Special Thanks...
    Yu tomoak-i@is.aist-nara.ac.jp,
    Mi hisho@tasihara.nest.or.jp,
    sunshine@sunshineco.com,
    and... Miss ARAI Akino(^^;)
 ----------------------------------------------------*/
#if defined(NeXT) && (NS_TARGET_MAJOR < 4)/* NeXTSTEP rld functions */

    {
        NXStream* s;
        unsigned long init_address;
        char *object_files[2] = {NULL, NULL};

        void (*init_fct)();
        
        object_files[0] = (char*)file;
        
        s = NXOpenFile(2,NX_WRITEONLY);

        /* Load object file, if return value ==0 ,  load failed*/
        if(rld_load(s, NULL, object_files, NULL) == 0) {
            NXFlush(s);
            NXClose(s);
            rb_loaderror("Failed to load %.200s", file);
        }

        /* lookup the initial function */
        if(rld_lookup(s, buf, &init_address) == 0) {
            NXFlush(s);
            NXClose(s);
            rb_loaderror("Failed to lookup Init function %.200s", file);
        }

        NXFlush(s);
        NXClose(s);

        /* Cannot call *init_address directory, so copy this value to
           funtion pointer */
        init_fct = (void(*)())init_address;
        (*init_fct)();
        return (void*)init_address;
    }
#else/* OPENSTEP dyld functions */
    {
        int dyld_result;
        NSObjectFileImage obj_file; /* handle, but not use it */
        /* "file" is module file name .
           "buf" is pointer to initial function name with "_" . */

        void (*init_fct)();


        dyld_result = NSCreateObjectFileImageFromFile(file, &obj_file);

        if (dyld_result != NSObjectFileImageSuccess) {
            rb_loaderror("Failed to load %.200s", file);
        }

        NSLinkModule(obj_file, file, NSLINKMODULE_OPTION_BINDNOW);

        /* lookup the initial function */
        if(!NSIsSymbolNameDefined(buf)) {
            rb_loaderror("Failed to lookup Init function %.200s",file);
        }       
        init_fct = NSAddressOfSymbol(NSLookupAndBindSymbol(buf));
        (*init_fct)();

        return (void*)init_fct;
    }
#endif /* rld or dyld */
#endif

#ifdef __BEOS__
# define DLN_DEFINED
    {
      status_t err_stat;  /* BeOS error status code */
      image_id img_id;    /* extention module unique id */
      void (*init_fct)(); /* initialize function for extention module */

      /* load extention module */
      img_id = load_add_on(file);
      if (img_id <= 0) {
        rb_loaderror("Failed to load %.200s", file);
      }
      
      /* find symbol for module initialize function. */
      /* The Be Book KernelKit Images section described to use
         B_SYMBOL_TYPE_TEXT for symbol of function, not
         B_SYMBOL_TYPE_CODE. Why ? */
      /* strcat(init_fct_symname, "__Fv"); */  /* parameter nothing. */
      /* "__Fv" dont need! The Be Book Bug ? */
      err_stat = get_image_symbol(img_id, buf,
                                  B_SYMBOL_TYPE_TEXT, (void **)&init_fct);

      if (err_stat != B_NO_ERROR) {
        char real_name[MAXPATHLEN];

        strcpy(real_name, buf);
        strcat(real_name, "__Fv");
        err_stat = get_image_symbol(img_id, real_name,
                                    B_SYMBOL_TYPE_TEXT, (void **)&init_fct);
      }

      if ((B_BAD_IMAGE_ID == err_stat) || (B_BAD_INDEX == err_stat)) {
        unload_add_on(img_id);
        rb_loaderror("Failed to lookup Init function %.200s", file);
      }
      else if (B_NO_ERROR != err_stat) {
        char errmsg[] = "Internal of BeOS version. %.200s (symbol_name = %s)";
        unload_add_on(img_id);
        rb_loaderror(errmsg, strerror(err_stat), buf);
      }

      /* call module initialize function. */
      (*init_fct)();
      return (void*)img_id;
    }
#endif /* __BEOS__*/

#ifdef __MACOS__
# define DLN_DEFINED
    {
      OSErr err;
      FSSpec libspec;
      CFragConnectionID connID;
      Ptr mainAddr;
      char errMessage[1024];
      Boolean isfolder, didsomething;
      Str63 fragname;
      Ptr symAddr;
      CFragSymbolClass class;
      void (*init_fct)();
      char fullpath[MAXPATHLEN];

      strcpy(fullpath, file);

      /* resolve any aliases to find the real file */
      c2pstr(fullpath);
      (void)FSMakeFSSpec(0, 0, fullpath, &libspec);
      err = ResolveAliasFile(&libspec, 1, &isfolder, &didsomething);
      if (err) {
          rb_loaderror("Unresolved Alias - %s", file);
      }

      /* Load the fragment (or return the connID if it is already loaded */
      fragname[0] = 0;
      err = GetDiskFragment(&libspec, 0, 0, fragname, 
                            kLoadCFrag, &connID, &mainAddr,
                            errMessage);
      if (err) {
          p2cstr(errMessage);
          rb_loaderror("%s - %s",errMessage , file);
      }

      /* Locate the address of the correct init function */
      c2pstr(buf);
      err = FindSymbol(connID, buf, &symAddr, &class);
      if (err) {
          rb_loaderror("Unresolved symbols - %s" , file);
      }
      init_fct = (void (*)())symAddr;
      (*init_fct)();
      return (void*)init_fct;
    }
#endif /* __MACOS__ */

#if defined(__VMS)
#define DLN_DEFINED
    {
        long status;
        void (*init_fct)();
        char *fname, *p1, *p2;

        $DESCRIPTOR(fname_d, "");
        $DESCRIPTOR(image_d, "");
        $DESCRIPTOR(buf_d, "");

        decc$to_vms(file, vms_fileact, 0, 0);

        fname = (char *)__alloca(strlen(file)+1);
        strcpy(fname,file);
        if (p1 = strrchr(fname,'/'))
            fname = p1 + 1;
        if (p2 = strrchr(fname,'.'))
            *p2 = '\0';

        fname_d.dsc$w_length  = strlen(fname);
        fname_d.dsc$a_pointer = fname;
        image_d.dsc$w_length  = strlen(vms_filespec);
        image_d.dsc$a_pointer = vms_filespec;
        buf_d.dsc$w_length    = strlen(buf);
        buf_d.dsc$a_pointer   = buf;

        lib$establish(vms_fisexh);

        status = lib$find_image_symbol (
                     &fname_d,
                     &buf_d, 
                     &init_fct, 
                     &image_d);

        lib$establish(0);

        if (status == RMS$_FNF) {
            error = dln_strerror();
            goto failed;
        } else if (!$VMS_STATUS_SUCCESS(status)) {
            error = DLN_ERROR();
            goto failed;
        }

        /* Call the init code */
        (*init_fct)();

        return 1;
    }
#endif /* __VMS */

#ifndef DLN_DEFINED
    rb_notimplement();
#endif

#endif /* USE_DLN_A_OUT */
#endif
#if !defined(_AIX) && !defined(NeXT)
  failed:
    rb_loaderror("%s - %s", error, file);
#endif

#endif /* NO_DLN_LOAD */
    return 0;                   /* dummy return */
}

static char *dln_find_1();

char *
dln_find_exe(fname, path)
    const char *fname;
    const char *path;
{
    if (!path) {
        path = getenv(PATH_ENV);
    }

    if (!path) {
#if defined(MSDOS) || defined(_WIN32) || defined(__human68k__) || defined(__MACOS__)
        path = "/usr/local/bin;/usr/ucb;/usr/bin;/bin;.";
#else
        path = "/usr/local/bin:/usr/ucb:/usr/bin:/bin:.";
#endif
    }
    return dln_find_1(fname, path, 1);
}

char *
dln_find_file(fname, path)
    const char *fname;
    const char *path;
{
#ifndef __MACOS__
    if (!path) path = ".";
    return dln_find_1(fname, path, 0);
#else
    if (!path) path = ".";
    return _macruby_path_conv_posix_to_macos(dln_find_1(fname, path, 0));
#endif
}

#if defined(__CYGWIN32__)
const char *
conv_to_posix_path(win32, posix, len)
    char *win32;
    char *posix;
    int len;
{
    char *first = win32;
    char *p = win32;
    char *dst = posix;

    posix[0] = '\0';
    for (p = win32; *p; p++)
        if (*p == ';') {
            *p = 0;
            cygwin32_conv_to_posix_path(first, posix);
            posix += strlen(posix);
            *posix++ = ':';
            first = p + 1;
            *p = ';';
        }
    if (len < strlen(first))
        fprintf(stderr, "PATH length too long: %s\n", first);
    else
        cygwin32_conv_to_posix_path(first, posix);
    return dst;
}
#endif

static char fbuf[MAXPATHLEN];

static char *
dln_find_1(fname, path, exe_flag)
    char *fname;
    char *path;
    int exe_flag;               /* non 0 if looking for executable. */
{
    register char *dp;
    register char *ep;
    register char *bp;
    struct stat st;
#ifdef __MACOS__
    const char* mac_fullpath;
#endif

    if (!fname) return fname;
    if (fname[0] == '/') return fname;
    if (strncmp("./", fname, 2) == 0 || strncmp("../", fname, 3) == 0)
      return fname;
    if (exe_flag && strchr(fname, '/')) return fname;
#ifdef DOSISH
    if (fname[0] == '\\') return fname;
# ifdef DOSISH_DRIVE_LETTER
    if (strlen(fname) > 2 && fname[1] == ':') return fname;
# endif
    if (strncmp(".\\", fname, 2) == 0 || strncmp("..\\", fname, 3) == 0)
      return fname;
    if (exe_flag && strchr(fname, '\\')) return fname;
#endif

    for (dp = path;; dp = ++ep) {
        register int l;
        int i;
        int fspace;

        /* extract a component */
        ep = strchr(dp, PATH_SEP[0]);
        if (ep == NULL)
            ep = dp+strlen(dp);

        /* find the length of that component */
        l = ep - dp;
        bp = fbuf;
        fspace = sizeof fbuf - 2;
        if (l > 0) {
            /*
            **  If the length of the component is zero length,
            **  start from the current directory.  If the
            **  component begins with "~", start from the
            **  user's $HOME environment variable.  Otherwise
            **  take the path literally.
            */

            if (*dp == '~' && (l == 1 ||
#if defined(DOSISH)
                               dp[1] == '\\' || 
#endif
                               dp[1] == '/')) {
                char *home;

                home = getenv("HOME");
                if (home != NULL) {
                    i = strlen(home);
                    if ((fspace -= i) < 0)
                        goto toolong;
                    memcpy(bp, home, i);
                    bp += i;
                }
                dp++;
                l--;
            }
            if (l > 0) {
                if ((fspace -= l) < 0)
                    goto toolong;
                memcpy(bp, dp, l);
                bp += l;
            }

            /* add a "/" between directory and filename */
            if (ep[-1] != '/')
                *bp++ = '/';
        }

        /* now append the file name */
        i = strlen(fname);
        if ((fspace -= i) < 0) {
          toolong:
            fprintf(stderr, "openpath: pathname too long (ignored)\n");
            *bp = '\0';
            fprintf(stderr, "\tDirectory \"%s\"\n", fbuf);
            fprintf(stderr, "\tFile \"%s\"\n", fname);
            goto next;
        }
        memcpy(bp, fname, i + 1);

#ifndef __MACOS__
        if (stat(fbuf, &st) == 0) {
            if (exe_flag == 0) return fbuf;
            /* looking for executable */
            if (!S_ISDIR(st.st_mode) && eaccess(fbuf, X_OK) == 0)
                return fbuf;
        }
#else
        if (mac_fullpath = _macruby_exist_file_in_libdir_as_posix_name(fbuf)) {
            if (exe_flag == 0) return mac_fullpath;
            /* looking for executable */
            if (stat(mac_fullpath, &st) == 0) {
                if (!S_ISDIR(st.st_mode) && eaccess(mac_fullpath, X_OK) == 0)
                    return mac_fullpath;
            }
        }
#endif
#if defined(DOSISH)
        if (exe_flag) {
            static const char *extension[] = {
#if defined(MSDOS)
                ".com", ".exe", ".bat",
#if defined(DJGPP)
                ".btm", ".sh", ".ksh", ".pl", ".sed",
#endif
#elif defined(__EMX__) || defined(_WIN32)
                ".exe", ".com", ".cmd", ".bat",
/* end of __EMX__ or _WIN32 */
#else
                ".r", ".R", ".x", ".X", ".bat", ".BAT",
/* __human68k__ */
#endif
                (char *) NULL
            };
            int j;

            for (j = 0; extension[j]; j++) {
                if (fspace < strlen(extension[j])) {
                    fprintf(stderr, "openpath: pathname too long (ignored)\n");
                    fprintf(stderr, "\tDirectory \"%.*s\"\n", (int) (bp - fbuf), fbuf);
                    fprintf(stderr, "\tFile \"%s%s\"\n", fname, extension[j]);
                    continue;
                }
                strcpy(bp + i, extension[j]);
#ifndef __MACOS__
                if (stat(fbuf, &st) == 0)
                    return fbuf;
#else
                if (mac_fullpath = _macruby_exist_file_in_libdir_as_posix_name(fbuf))
                    return mac_fullpath;

#endif
            }
        }
#endif /* MSDOS or _WIN32 or __human68k__ or __EMX__ */

      next:
        /* if not, and no other alternatives, life is bleak */
        if (*ep == '\0') {
            return NULL;
        }

        /* otherwise try the next component in the search path */
    }
}

#if defined(__VMS)

/* action routine for decc$to_vms */
static int vms_fileact(char *filespec, int type)
{
    if (vms_filespec)
        free(vms_filespec);
    vms_filespec = malloc(strlen(filespec)+1);
    strcpy(vms_filespec, filespec);
    return 1;
}

/* exception handler for LIB$FIND_IMAGE_SYMBOL */
static long vms_fisexh(long *sigarr, long *mecarr)
{
    sys$unwind(1, 0);
    return 1;
}

#endif /* __VMS */

---