Re: Run-time dynamic linking in grep

[Reuben Thomas]

On 26 January 2011 17:53, Jim Meyering <address@hidden> wrote:
>
> Also, "make syntax-check" failed due to a useless <assert.h>

What's a good way to build that into my workflow (preferably without
running it explicitly), e.g. getting make distcheck to do it?

> Most importantly, non-seekable (pipe) input is not decompressed:
> (that "null" looks suspicious, too)
>
>    $ echo foo|gzip|src/grep --decompress o
>    src/grep: (null): Illegal seek
>
> It would sure be nice to fix that.

This is a pain. The null is easy: I had misunderstood the format of
the error() calls, and shouldn't've been passing file to error when
file was null.

The not seeking is harder. If transparent decompression is going to
cope with pipes (and if not, one might as well just use a zgrep
wrapper), then I can't seek in zio.c. But if I can't seek, then I
can't check the magic by loading it in before calling a function like
gzdopen. And gzdopen won't tell me whether it is actually
uncompressing or not; and in any case, it will presumably read some
data, so I will be left without a virgin descriptor that I can pass on
to BZ2_bzdopen.

In short, I can't think of a way to use the compression veneers to do
what I want; it looks like I'll have to adapt them instead (so I can
read the magic, check it, and then implement manual buffering to feed
the relevant decompression function).

This will take a bit of work, so before I start, any other suggestions welcomed.

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