1 files changed, 39 insertions, 0 deletions
diff --git a/gl/m4/readlinkat.m4 b/gl/m4/readlinkat.m4
new file mode 100644
index 0000000..63c5205
--- /dev/null
+++ b/gl/m4/readlinkat.m4
@@ -0,0 +1,39 @@
+# serial 6
+# See if we need to provide readlinkat replacement.
+
+dnl Copyright (C) 2009-2022 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+# Written by Eric Blake.
+
+AC_DEFUN([gl_FUNC_READLINKAT],
+[
+  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+  AC_CHECK_FUNCS_ONCE([readlinkat])
+  AC_REQUIRE([gl_FUNC_READLINK])
+  if test $ac_cv_func_readlinkat = no; then
+    HAVE_READLINKAT=0
+  else
+    AC_CACHE_CHECK([whether readlinkat signature is correct],
+      [gl_cv_decl_readlinkat_works],
+      [AC_COMPILE_IFELSE(
+         [AC_LANG_PROGRAM(
+           [[#include <unistd.h>
+             /* Check whether original declaration has correct type.  */
+             ssize_t readlinkat (int, char const *, char *, size_t);]])],
+         [gl_cv_decl_readlinkat_works=yes],
+         [gl_cv_decl_readlinkat_works=no])])
+    # Assume readlinkat has the same bugs as readlink,
+    # as is the case on OS X 10.10 with trailing slashes.
+    case $gl_cv_decl_readlinkat_works,$gl_cv_func_readlink_trailing_slash,$gl_cv_func_readlink_truncate in
+      *yes,*yes,*yes)
+        ;;
+      *)
+        REPLACE_READLINKAT=1
+        ;;
+    esac
+  fi
+])