Re: areadlinkat

[Eric Blake]

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According to Eric Blake on 10/7/2009 11:00 AM:
> Eric Blake (4):
>       areadlink, areadlink-with-size: add tests
>       areadlinkat: new module

>  2009-10-07  Eric Blake  <address@hidden>
> 
> +     areadlinkat: new module
> +     * lib/at-func.c (FUNC_FAIL): New define.
> +     (AT_FUNC_NAME, VALIDATE_FLAG): Use it rather than raw -1.

Oops - I missed one instance relating to FUNC_FAIL.  test-areadlinkat was
failing on older Linux, because /proc/self/fd/-1/name gave ENOENT rather
than EBADF.  But since 0 <= char* was always true, the fallback code that
converts ENOENT into the correct error was never triggered.
areadlinkat-with-size was the only other impacted client of at-func.c.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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>From e35809901f94acb04ccc325d9ef1b0eed6cedd81 Mon Sep 17 00:00:00 2001
From: Eric Blake <address@hidden>
Date: Wed, 21 Oct 2009 21:01:41 -0600
Subject: [PATCH] areadlinkat: avoid failure on older glibc

Acting on /proc/self/-1/name gives ENOTDIR, not EBADF.  at-func
normally fell back to fchdir, which discovered the real problem
of invalid fd, but mistakenly short-circuited when FUNC_FAIL was
NULL (since 0<=(char*)result is always true).

* lib/at-func.c (AT_FUNC_NAME): Check for explicit FUNC_FAIL,
rather than mis-comparing 0 against FUNC_RESULT of char*.

Signed-off-by: Eric Blake <address@hidden>
---
 ChangeLog     |    6 ++++++
 lib/at-func.c |    2 +-
 2 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 806c4a6..c08b844 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2009-10-21  Eric Blake  <address@hidden>
+
+       areadlinkat: avoid failure on older glibc
+       * lib/at-func.c (AT_FUNC_NAME): Check for explicit FUNC_FAIL,
+       rather than mis-comparing 0 against FUNC_RESULT of char*.
+
 2009-10-21  Bruno Haible  <address@hidden>

        * modules/stpncpy (License): Relicense under LGPLv2+.
diff --git a/lib/at-func.c b/lib/at-func.c
index b6aa0fd..cc7bfc2 100644
--- a/lib/at-func.c
+++ b/lib/at-func.c
@@ -84,7 +84,7 @@ AT_FUNC_NAME (int fd, char const *file 
AT_FUNC_POST_FILE_PARAM_DECLS)
         /* If the syscall succeeds, or if it fails with an unexpected
            errno value, then return right away.  Otherwise, fall through
            and resort to using save_cwd/restore_cwd.  */
-        if (0 <= proc_result)
+        if (FUNC_FAIL != proc_result)
           return proc_result;
         if (! EXPECTED_ERRNO (proc_errno))
           {
-- 
1.6.5.rc1