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Re: bootstrapping SED-4.5, circular dependency?

From: Jan Nieuwenhuizen
Subject: Re: bootstrapping SED-4.5, circular dependency?
Date: Sun, 09 Dec 2018 04:52:35 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux)

Assaf Gordon writes:

Hello Assaf,

> Technically speaking, these kind of dependencies (e.g. needing SED
> to build a package) arise from autotools, not directly from sed's
> build commands.

Ah yes, course.  That is a big difference.

>> Here is what I get:
> [...]
>> ERROR: In procedure scm-error:
>> SED: command not supported: "/^.*\\/\\([^/][^/]*\\)\\/*$/{\n\t    
>> s//\\1/\n\t    q\n\t  }\n\t  /^X\\/\\(\\/\\/\\)$/{\n\t    s//\\1/\n\t    
>> q\n\t  }\n\t  /^X\\/\\(\\/\\).*/{\n\t    s//\\1/\n\t    q\n\t  }\n\t  
>> s/.*/./; q"
> The failed sed program is (transcribed from the above error message)
> ====
> /^.*\/\([^/][^/]*\)\/*$/{
>           s//\1/
>           q
>         }
>   /^X\/\(\/\/\)$/{
>           s//\1/
>           q
>   }
>   /^X\/\(\/\).*/{
>           s//\1/
>           q
>   }
>   s/.*/./; q
> ====
> It is a very standard sed program, which should (and does) work on every
> existing SED implementation (posix-compliant of course).

Right, now I see.  I really only catered for plain `-e s,,,' commands.

> I would recommend adjusting your sed implementation to support
> these commands, because you'll encounter them in many packages
> that use autotools.

That's sounds like the right thing to do, thanks!

> Digging a bit further, I see this specific sed program originates
> from autoconf, from the M4 code used to implement basename and dirname,
> e.g. here:
> So it means every autotools package that uses these macros (and there
> are many) will cause the same issue.
> The best solution is likely to implement these sed commands in your
> sed implementation (if you need help in testing I'm happy to try,
> though I know very little about guile).

That is even more helpful!  While I still think we should support the
simple SED script above, there could be a problem with basename/dirname.
Solving that might even sidestep this SED feature.  Many options now!

> As a last resort, I can think of a really ugly hack:
> create a "fake sed" wrapper script in guile,
> that checks if the given SED script is one that you don't implement
> (e.g. the one above). If it is, since we know all it does is
> basename/dirname - just call a real dirname/basename instead of
> using sed's regexes. Otherwise, pass the parameters to the real
> guile-sed.
> Put this guile-sed-wrapper in $PATH, and it might just work...
> In a completely different approach, since you are trying to bootstrap:
> building OpenBSD's sed binary is very easy (needs just a C compiler
> and works fine on GNU/Linux) - perhaps building it
> would be faster as a first step to get a working sed, then use it
> to build other packages (I can help with that if you want, send me an
> email).

Many thanks, also for these two last resort options!  I'm sure we'll
manage to bootstrap SED.  I'll let you know how it goes.


Jan Nieuwenhuizen <address@hidden> | GNU LilyPond
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