Use of chmod in gnulib

Use of chmod in gnulib

[Jeffrey Walton]

Hi Everyone,

According to the Autoconf manual, commands like 'chmod +x' should be
avoided in favor of 'chmod a+x'. I believe the same applies to 'chmod
-w' and friends. Also see
https://www.gnu.org/software/autoconf/manual/autoconf-2.69/html_node/Limitations-of-Usual-Tools.html.

It looks like there are some of the earlier in the gnulib sources:

$grep -IR 'chmod +' ./*
./gnulib/tests/test-set-mode-acl.sh:            /bin/chmod +a
"user:daemon allow execute" tmpfile0
./gnulib/tests/test-copy-file.sh:        /bin/chmod +a "user:daemon
allow execute" tmpfile0
./gnulib/tests/test-copy-file.sh:        /bin/chmod +a "group:daemon
allow read" tmpfile0
./gnulib/tests/test-copy-acl.sh:        /bin/chmod +a "user:daemon
allow execute" tmpfile0
./gnulib/tests/test-copy-acl.sh:        /bin/chmod +a "group:daemon
allow read" tmpfile0
./gnulib/tests/test-file-has-acl.sh:        /bin/chmod +a "user:daemon
allow execute" tmpfile0
./gnulib/m4/progtest.m4:chmod +x conf$$.file
./gnulib_test/gltests/test-set-mode-acl.sh:            /bin/chmod +a
"user:daemon allow execute" tmpfile0
./gnulib_test/gltests/test-copy-file.sh:        /bin/chmod +a
"user:daemon allow execute" tmpfile0
./gnulib_test/gltests/test-copy-file.sh:        /bin/chmod +a
"group:daemon allow read" tmpfile0
./gnulib_test/gltests/test-copy-acl.sh:        /bin/chmod +a
"user:daemon allow execute" tmpfile0
./gnulib_test/gltests/test-copy-acl.sh:        /bin/chmod +a
"group:daemon allow read" tmpfile0
./gnulib_test/gltests/test-file-has-acl.sh:        /bin/chmod +a
"user:daemon allow execute" tmpfile0
./gnulib_test/configure:  chmod +x "$as_me.lineno" ||
./gnulib_test/configure:test $as_write_fail = 0 && chmod +x
$CONFIG_STATUS || ac_write_fail=1

Re: Use of chmod in gnulib

[Paul Eggert]

On 3/22/20 10:17 AM, Jeffrey Walton wrote:

> According to the Autoconf manual, commands like 'chmod +x' should be
> avoided in favor of 'chmod a+x'. I believe the same applies to 'chmod
> -w' and friends. Also see
> https://www.gnu.org/software/autoconf/manual/autoconf-2.69/html_node/Limitations-of-Usual-Tools.html.
> 
> It looks like there are some of the earlier in the gnulib sources:

Those uses look safe to me. Either they're 'chmod +a' which is a macOS extension 
and so the Autoconf advice doesn't apply, or they're 'chmod +x' on a newly 
created file which is safe unless someone has a purposely-harmful and 
unsupported umask like 0777 which will break 'configure' in countless other ways.

Re: Use of chmod in gnulib

[Jeffrey Walton]

On Sun, Mar 22, 2020 at 3:18 PM Paul Eggert <eggert@cs.ucla.edu> wrote:
>
> On 3/22/20 10:17 AM, Jeffrey Walton wrote:
>
> > According to the Autoconf manual, commands like 'chmod +x' should be
> > avoided in favor of 'chmod a+x'. I believe the same applies to 'chmod
> > -w' and friends. Also see
> > https://www.gnu.org/software/autoconf/manual/autoconf-2.69/html_node/Limitations-of-Usual-Tools.html.
> >
> > It looks like there are some of the earlier in the gnulib sources:
>
> Those uses look safe to me. Either they're 'chmod +a' which is a macOS extension
> and so the Autoconf advice doesn't apply, or they're 'chmod +x' on a newly
> created file which is safe unless someone has a purposely-harmful and
> unsupported umask like 0777 which will break 'configure' in countless other ways.

If that's true, then it sounds like the manual is wrong and the manual
should be updated.

Jeff