Re: missing backslash escaping in AC_TRY_EVAL yields binary data in config.log with dash

[Vincent Lefevre]

On 2018-10-02 09:31:33 -0400, Nick Bowler wrote:
> Drilling into the Autoconf source, we find that this is intentional:
> 
>   # The AC_TRY_EVAL and AC_TRY_COMMAND macros are dangerous and
>   # undocumented, and should not be used.
>   # They may be removed or their API changed in a future release.
>   # Autoconf itself no longer uses these two macros; they are present
>   # only for backward compatibility with previous versions of Autoconf.
>   # Not every shell command will work due to problems with eval
>   # and quoting, and the rules for exactly what does work are tricky.
>   # Worse, due to double-expansion during evaluation, arbitrary unintended
>   # shell commands could be executed in some situations.
> 
> If libtool is still using this macro, and it is causing problems,
> then this does seem like a bug in libtool.  The solution would seem
> to be for libtool to stop using AC_TRY_EVAL.

This is what I've seen too, but I fear that as long as it is not
removed from autoconf, this will never be done. IMHO, a replacement
should be proposed and these macros should be removed. Or these
macros should be fixed and documented.

In the mean time, I wrote a patch for libtool[*] to replace the
occurrence that was generating binary data.

[*] https://debbugs.gnu.org/cgi/bugreport.cgi?bug=21309#19

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Vincent Lefèvre <address@hidden> - Web: <https://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)