Re: make lchmodat friendlier

[Eric Blake]

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According to Jim Meyering on 9/6/2009 11:49 PM:
>> Also, should "openat.h" provide shortcuts named:
>>
>> accessat() => faccessat(,0)
>> euidaccessat() => faccessat(,AT_EACCESS)
>> statat() => fstatat(,0)
>> lstatat() => fstatat(,AT_SYMLINK_NOFOLLOW)
>>
>> to match the existing shortcuts of chownat, lchownat, etc.
> 
> Good idea.
> I hesitated to appropriate the names initially, but the combination
> of increased readability and orthogonality make it worthwhile.

Done as follows.

Unfortunately, the naming of unlinkat prevents doing:

unlinkat() => unlinkat(,0)

so, I did not do this (even though I debated about it):

rmdirat() => unlinkat(,AT_REMOVEDIR)

Likewise, once we have support, we could do:

lutimensat() => utimensat(,AT_SYMLINK_NOFOLLOW)

but not utimensat.  And I don't know of any good naming for the two
variants of linkat (there is no well-known short name that indicates
whether link will hard-link a symlink or follow it).

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

Eric Blake             address@hidden
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>From 370fec14f2e177cf533cb967e2dc04354e883c45 Mon Sep 17 00:00:00 2001
From: Eric Blake <address@hidden>
Date: Mon, 7 Sep 2009 05:28:13 -0600
Subject: [PATCH] openat: provide more convenience names

* modules/faccessat (configure.ac): Add C witness.
* lib/unistd.in.h (readlinkat): Fix typo.
* lib/openat.h (statat, lstatat, accessat, euidaccessat): New
convenience wrappers.
* top/maint.mk (sc_prohibit_openat_without_use): Allow these
wrappers in syntax checks.

Signed-off-by: Eric Blake <address@hidden>
---
 ChangeLog         |   10 ++++++++++
 lib/openat.h      |   30 ++++++++++++++++++++++++++++++
 lib/unistd.in.h   |    2 +-
 modules/faccessat |    1 +
 top/maint.mk      |    2 +-
 5 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 04e5cc1..f7ac99c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2009-09-07  Eric Blake  <address@hidden>
+
+       openat: provide more convenience names
+       * modules/faccessat (configure.ac): Add C witness.
+       * lib/unistd.in.h (readlinkat): Fix typo.
+       * lib/openat.h (statat, lstatat, accessat, euidaccessat): New
+       convenience wrappers.
+       * top/maint.mk (sc_prohibit_openat_without_use): Allow these
+       wrappers in syntax checks.
+
 2009-09-06  Eric Blake  <address@hidden>

        doc: fix comments in recent patches
diff --git a/lib/openat.h b/lib/openat.h
index 1d8596f..433b998 100644
--- a/lib/openat.h
+++ b/lib/openat.h
@@ -81,4 +81,34 @@ lchmodat (int fd, char const *file, mode_t mode)
   return fchmodat (fd, file, mode, AT_SYMLINK_NOFOLLOW);
 }

+static inline int
+statat (int fd, char const *name, struct stat *st)
+{
+  return fstatat (fd, name, st, 0);
+}
+
+static inline int
+lstatat (int fd, char const *name, struct stat *st)
+{
+  return fstatat (fd, name, st, AT_SYMLINK_NOFOLLOW);
+}
+
+#if GNULIB_FACCESSAT
+/* For now, there are no wrappers named laccessat or leuidaccessat,
+   since gnulib doesn't support faccessat(,AT_SYMLINK_NOFOLLOW) and
+   since access rights on symlinks are of limited utility.  */
+
+static inline int
+accessat (int fd, char const *file, int mode)
+{
+  return faccessat (fd, file, mode, 0);
+}
+
+static inline int
+euidaccessat (int fd, char const *file, int mode)
+{
+  return faccessat (fd, file, mode, AT_EACCESS);
+}
+#endif
+
 #endif /* _GL_HEADER_OPENAT */
diff --git a/lib/unistd.in.h b/lib/unistd.in.h
index 6503529..902b025 100644
--- a/lib/unistd.in.h
+++ b/lib/unistd.in.h
@@ -208,7 +208,7 @@ ssize_t readlinkat (int fd, char const *file, char *buf, 
size_t len);
 #elif defined GNULIB_POSIXCHECK
 # undef readlinkat
 # define readlinkat(d,n,b,l)                        \
-    (GL_LINK_WARNING ("faccessat is not portable - " \
+    (GL_LINK_WARNING ("readlinkat is not portable - " \
                       "use gnulib module symlinkat for portability"), \
      readlinkat (d, n, b, l))
 #endif
diff --git a/modules/faccessat b/modules/faccessat
index d7737ba..92d8185 100644
--- a/modules/faccessat
+++ b/modules/faccessat
@@ -14,6 +14,7 @@ unistd

 configure.ac:
 gl_FUNC_FACCESSAT
+gl_MODULE_INDICATOR([faccessat])
 gl_UNISTD_MODULE_INDICATOR([faccessat])

 Makefile.am:
diff --git a/top/maint.mk b/top/maint.mk
index 45bc0c9..c0c3f27 100644
--- a/top/maint.mk
+++ b/top/maint.mk
@@ -295,7 +295,7 @@ sc_prohibit_root_dev_ino_without_use:

 sc_prohibit_openat_without_use:
        @h='"openat.h"' \
-       
re='\<(openat_(permissive|needs_fchdir|(save|restore)_fail)|l?ch(own|mod)at)\>' 
\
+       
re='\<(openat_(permissive|needs_fchdir|(save|restore)_fail)|l?(stat|ch(own|mod))at|(euid)?accessat)\>'
 \
          $(_header_without_use)

 # Prohibit the inclusion of c-ctype.h without an actual use.
-- 
1.6.3.3.334.g916e1