[PATCH] drop lchmod

[PATCH] drop lchmod

[Julien Ramseier]

lchmod is not POSIX and not supported on Linux.
Keeping it would probably do more harm than good: software checking 
for its presence (i.e. libarchive) will use it and always fail.


diff --git a/include/sys/stat.h b/include/sys/stat.h
index 9d09662..0058338 100644
--- a/include/sys/stat.h
+++ b/include/sys/stat.h
@@ -92,7 +92,6 @@ int futimens(int, const struct timespec [2]);
 int utimensat(int, const char *, const struct timespec [2], int);

 #if defined(_GNU_SOURCE) || defined(_BSD_SOURCE)
-int lchmod(const char *, mode_t);
 #define S_IREAD S_IRUSR
 #define S_IWRITE S_IWUSR
 #define S_IEXEC S_IXUSR
diff --git a/src/stat/lchmod.c b/src/stat/lchmod.c
deleted file mode 100644
index f324ba7..0000000
--- a/src/stat/lchmod.c
+++ /dev/null
@@ -1,8 +0,0 @@
-#define _GNU_SOURCE
-#include <sys/stat.h>
-#include <fcntl.h>
-
-int lchmod(const char *path, mode_t mode)
-{
-   return fchmodat(AT_FDCWD, path, mode, AT_SYMLINK_NOFOLLOW);
-}

Re: [PATCH] drop lchmod

[Rich Felker]

On Wed, Jan 04, 2017 at 10:23:55PM +0100, Julien Ramseier wrote:
> lchmod is not POSIX and not supported on Linux.
> Keeping it would probably do more harm than good: software checking 
> for its presence (i.e. libarchive) will use it and always fail.
> 
> 
> diff --git a/include/sys/stat.h b/include/sys/stat.h
> index 9d09662..0058338 100644
> --- a/include/sys/stat.h
> +++ b/include/sys/stat.h
> @@ -92,7 +92,6 @@ int futimens(int, const struct timespec [2]);
>  int utimensat(int, const char *, const struct timespec [2], int);
> 
>  #if defined(_GNU_SOURCE) || defined(_BSD_SOURCE)
> -int lchmod(const char *, mode_t);
>  #define S_IREAD S_IRUSR
>  #define S_IWRITE S_IWUSR
>  #define S_IEXEC S_IXUSR
> diff --git a/src/stat/lchmod.c b/src/stat/lchmod.c
> deleted file mode 100644
> index f324ba7..0000000
> --- a/src/stat/lchmod.c
> +++ /dev/null
> @@ -1,8 +0,0 @@
> -#define _GNU_SOURCE
> -#include <sys/stat.h>
> -#include <fcntl.h>
> -
> -int lchmod(const char *path, mode_t mode)
> -{
> -   return fchmodat(AT_FDCWD, path, mode, AT_SYMLINK_NOFOLLOW);
> -}

This can't be done because it's ABI. It will cause any program linked
with a reference to lchmod to failto execute with missing symbol
errors.

libarchive needs to be fixed to respect the errno value. fchmodat with
AT_FDCWD and the AT_SYMLINK_NOFOLLOW flag is semantically equivalent
to lchmod and is required by POSIX, so software should be prepared to
deal with systems where the error EOPNOTSUPP occurs.

Rich

Re: [PATCH] drop lchmod

[A. Wilcox]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

On 04/01/17 15:35, Rich Felker wrote:

> libarchive needs to be fixed to respect the errno value.

https://github.com/libarchive/libarchive/commit/65fe103

We had to ship this patch in Adélie for the v3.1.x branch, but 3.2+
integrates it, and it works fine on musl without patching here.

Julien, can you reproduce any sort of failure with libarchive-3.2 or
newer?  Or is this in another package?  Perhaps more information would
be useful.  At any rate, there is no reason to drop this function.

- --arw


- -- 
A. Wilcox (awilfox)
Project Lead, Adélie Linux
http://adelielinux.org
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Re: [PATCH] drop lchmod

[Julien Ramseier]

> Le 5 janv. 2017 à 01:39, A. Wilcox <awilfox@adelielinux.org> a écrit :
> 
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA256
> 
> On 04/01/17 15:35, Rich Felker wrote:
> 
>> libarchive needs to be fixed to respect the errno value.
> 
> https://github.com/libarchive/libarchive/commit/65fe103
> 
> We had to ship this patch in Adélie for the v3.1.x branch, but 3.2+
> integrates it, and it works fine on musl without patching here.
> 
> Julien, can you reproduce any sort of failure with libarchive-3.2 or
> newer?  Or is this in another package?  Perhaps more information would
> be useful.  At any rate, there is no reason to drop this function.
> 

Indeed I was using an older version and had not noticed this was fixed.

I keep forgetting about ABI breakages (since I don't care about them
in my use case) and send stupid patches...

- J