I did:
> * tests/test-readlink.h (test_readlink): Add a test of /dev/null.
and now I get a failure of test-readlinkat:
FAIL: test-readlinkat
=====================
../../gltests/test-readlink.h:120: assertion 'result == -1 || buf[0] != '\\''
failed
Stack trace:
0x40243d print_stack_trace
../../gllib/abort-debug.c:40
0x40243d _gl_pre_abort
../../gllib/abort-debug.c:81
0x402372 test_readlink
../../gltests/test-readlink.h:120
0x4127a0 main
../../gltests/test-readlinkat.c:75
This patch should fix it.
2024-06-03 Bruno Haible <[email protected]>
readlinkat: Work around a Cygwin 3.3.6 bug.
* m4/readlinkat.m4 (gl_FUNC_READLINKAT): Set REPLACE_READLINKAT to 1 on
Cygwin.
* lib/readlinkat.c (rpl_readlinkat): On Cygwin, for /dev/* files, don't
return results that start with a backslash.
* doc/posix-functions/readlinkat.texi: Mention the Cygwin bug.
diff --git a/doc/posix-functions/readlinkat.texi
b/doc/posix-functions/readlinkat.texi
index 503de65e9e..2384bcb2c8 100644
--- a/doc/posix-functions/readlinkat.texi
+++ b/doc/posix-functions/readlinkat.texi
@@ -19,6 +19,10 @@
On some platforms, this function returns @code{int} instead of
@code{ssize_t}:
AIX 7.1.
+@item
+For the file name @file{/dev/null}, this function returns @file{\Device\Null},
+which is unusable, on some platforms:
+Cygwin 3.3.6.
@end itemize
Portability problems mostly fixed by Gnulib:
diff --git a/lib/readlinkat.c b/lib/readlinkat.c
index faf85401ae..f4d64c0d13 100644
--- a/lib/readlinkat.c
+++ b/lib/readlinkat.c
@@ -79,6 +79,16 @@ rpl_readlinkat (int fd, char const *file, char *buf, size_t
bufsize)
}
# endif
+# if defined __CYGWIN__
+ /* On Cygwin 3.3.6, readlinkat(AT_FDCWD,"/dev/null") returns
"\\Device\\Null",
+ which is unusable. Better fail with EINVAL. */
+ if (r > 0 && strncmp (file, "/dev/", 5) == 0 && buf[0] == '\\')
+ {
+ errno = EINVAL;
+ return -1;
+ }
+# endif
+
return r;
}
diff --git a/m4/readlinkat.m4 b/m4/readlinkat.m4
index 8a33c16913..1f091e8b63 100644
--- a/m4/readlinkat.m4
+++ b/m4/readlinkat.m4
@@ -1,5 +1,5 @@
# readlinkat.m4
-# serial 8
+# serial 9
dnl Copyright (C) 2009-2024 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
@@ -27,9 +27,12 @@ AC_DEFUN([gl_FUNC_READLINKAT]
[AC_LANG_PROGRAM(
[[#include <unistd.h>
/* Check whether original declaration has correct type. */
- ssize_t readlinkat (int, char const *, char *, size_t);]])],
+ ssize_t readlinkat (int, char const *, char *, size_t);
+ ]])
+ ],
[gl_cv_decl_readlinkat_works=yes],
- [gl_cv_decl_readlinkat_works=no])])
+ [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,$gl_cv_func_readlink_truncate
in
@@ -39,5 +42,13 @@ AC_DEFUN([gl_FUNC_READLINKAT]
REPLACE_READLINKAT=1
;;
esac
+
+ dnl On Cygwin 3.3.6, readlinkat(AT_FDCWD,"/dev/null") returns
+ dnl "\\Device\\Null", which is unusable.
+ case "$host_os" in
+ cygwin*)
+ REPLACE_READLINKAT=1
+ ;;
+ esac
fi
])
