[BusyBox] busybox, sed, and zlib's configure script

[Glenn McGrath]

On Mon, 22 Sep 2003 04:16:31 -0400
Rob Landley <rob at landley.net> wrote:

> I'm not sure if the problem is busybox producing an invalid config or
> some bug in uclibc coming out of the woodwork.  I'm going to do a
> static build of ld with the straight gnu toolchain (glibc, gnu sed,
> etc.) and compare the config to see if that reveals anything obvious,
> then re-introduce uclibc and busybox separately to try to narrow this
> down.

When i was testing to see if busybox could build a correct Makefile, i
just made one in each environment and did a diff. 
 
> Oh, one more thing: in order to get binutils to configure properly,
> sed needs the newline matching hack enabled.  What exactly IS the
> warning regarding that?  (Some kind of standards violation?  The meat
> of the hack seems to replace \n with \\n, but there's some other
> ifdefs I didnt'have time to trace throught due to playing with
> experimental kernels.)

The hack modifies the pattern prior to it being processed by the regcomp
command.
It also modifies the text before and after the regex is applied to it.

I put some more #ifdef's in recently, it defines different behaviour
between GNU sed and posix sed.

I put the newline warning in because i expected it to break something,
but i couldnt think of any other way around the problem without
rewriting regex handling. (the problem being libc's dont support pattern
matching with a newline character as part of the pattern.

Now looking at the standard for regex (1) it says
"If REG_NEWLINE is not set in cflags, then a <newline> in pattern or
string shall be treated as an ordinary character."
Ive tried with and without REG_NEWLINE being set in glibc and it doesnt
work in either case, maybe its a bug in glibc, i havent tested it in
uclibc.

1) http://www.opengroup.org/onlinepubs/007904975/functions/regcomp.html


> What's a test case that would fail because of this hack being enabled?

This works

$ echo "\n" | sed 's/\\n/foo/'
foo
$ echo "\n" | ./busybox sed 's/\\n/foo/'
\foo


These dont
$ echo "\n" | sed 's/\n/foo/'
\n
$ echo "\n" | ./busybox sed 's/\n/foo/'
\foo


$ echo "\n" | sed 's/\\\n/foo/'
\n
$ echo "\n" | ./busybox sed 's/\\\n/foo/'
foo