readlink.m4 revision 1.3 
1# readlink.m4 serial 16
2dnl Copyright (C) 2003, 2007, 2009-2022 Free Software Foundation, Inc.
3dnl This file is free software; the Free Software Foundation
4dnl gives unlimited permission to copy and/or distribute it,
5dnl with or without modifications, as long as this notice is preserved.
6
7AC_DEFUN([gl_FUNC_READLINK],
8[
9  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
10  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
11  AC_CHECK_FUNCS_ONCE([readlink])
12  if test $ac_cv_func_readlink = no; then
13    HAVE_READLINK=0
14  else
15    AC_CACHE_CHECK([whether readlink signature is correct],
16      [gl_cv_decl_readlink_works],
17      [AC_COMPILE_IFELSE(
18         [AC_LANG_PROGRAM(
19           [[#include <unistd.h>
20      /* Cause compilation failure if original declaration has wrong type.  */
21      ssize_t readlink (const char *, char *, size_t);]])],
22         [gl_cv_decl_readlink_works=yes], [gl_cv_decl_readlink_works=no])])
23    dnl Solaris 9 ignores trailing slash.
24    dnl FreeBSD 7.2 dereferences only one level of links with trailing slash.
25    AC_CACHE_CHECK([whether readlink handles trailing slash correctly],
26      [gl_cv_func_readlink_trailing_slash],
27      [# We have readlink, so assume ln -s works.
28       ln -s conftest.no-such conftest.link
29       ln -s conftest.link conftest.lnk2
30       AC_RUN_IFELSE(
31         [AC_LANG_PROGRAM(
32           [[#include <unistd.h>
33]], [[char buf[20];
34      return readlink ("conftest.lnk2/", buf, sizeof buf) != -1;]])],
35         [gl_cv_func_readlink_trailing_slash=yes],
36         [gl_cv_func_readlink_trailing_slash=no],
37         [case "$host_os" in
38            # Guess yes on Linux or glibc systems.
39            linux-* | linux | *-gnu* | gnu*)
40              gl_cv_func_readlink_trailing_slash="guessing yes" ;;
41            # Guess no on AIX or HP-UX.
42            aix* | hpux*)
43              gl_cv_func_readlink_trailing_slash="guessing no" ;;
44            # If we don't know, obey --enable-cross-guesses.
45            *)
46              gl_cv_func_readlink_trailing_slash="$gl_cross_guess_normal" ;;
47          esac
48         ])
49      rm -f conftest.link conftest.lnk2])
50    case "$gl_cv_func_readlink_trailing_slash" in
51      *yes)
52        if test "$gl_cv_decl_readlink_works" != yes; then
53          REPLACE_READLINK=1
54        fi
55        ;;
56      *)
57        AC_DEFINE([READLINK_TRAILING_SLASH_BUG], [1], [Define to 1 if readlink
58          fails to recognize a trailing slash.])
59        REPLACE_READLINK=1
60        ;;
61    esac
62
63    AC_CACHE_CHECK([whether readlink truncates results correctly],
64      [gl_cv_func_readlink_truncate],
65      [# We have readlink, so assume ln -s works.
66       ln -s ab conftest.link
67       AC_RUN_IFELSE(
68         [AC_LANG_PROGRAM(
69           [[#include <unistd.h>
70]], [[char c;
71      return readlink ("conftest.link", &c, 1) != 1;]])],
72         [gl_cv_func_readlink_truncate=yes],
73         [gl_cv_func_readlink_truncate=no],
74         [case "$host_os" in
75            # Guess yes on Linux or glibc systems.
76            linux-* | linux | *-gnu* | gnu*)
77              gl_cv_func_readlink_truncate="guessing yes" ;;
78            # Guess no on AIX or HP-UX.
79            aix* | hpux*)
80              gl_cv_func_readlink_truncate="guessing no" ;;
81            # If we don't know, obey --enable-cross-guesses.
82            *)
83              gl_cv_func_readlink_truncate="$gl_cross_guess_normal" ;;
84          esac
85         ])
86      rm -f conftest.link conftest.lnk2])
87    case $gl_cv_func_readlink_truncate in
88      *yes)
89        if test "$gl_cv_decl_readlink_works" != yes; then
90          REPLACE_READLINK=1
91        fi
92        ;;
93      *)
94        AC_DEFINE([READLINK_TRUNCATE_BUG], [1], [Define to 1 if readlink
95          sets errno instead of truncating a too-long link.])
96        REPLACE_READLINK=1
97        ;;
98    esac
99  fi
100])
101
102# Like gl_FUNC_READLINK, except prepare for separate compilation
103# (no REPLACE_READLINK, no AC_LIBOBJ).
104AC_DEFUN([gl_FUNC_READLINK_SEPARATE],
105[
106  AC_CHECK_FUNCS_ONCE([readlink])
107  gl_PREREQ_READLINK
108])
109
110# Prerequisites of lib/readlink.c.
111AC_DEFUN([gl_PREREQ_READLINK],
112[
113  :
114])
115