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Re: [PATCH 2/3] scratch_buffer: new module

From: Paul Eggert
Subject: Re: [PATCH 2/3] scratch_buffer: new module
Date: Sat, 2 Sep 2017 02:11:27 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1

Florian Weimer wrote:
This configure test is invalid because __libc_scratch_buffer_grow is a
GLIBC_PRIVATE symbol not part of the ABI.

You really need to rename those __libc_* functions because they are in
the internal glibc namespace.

Done by installing the first attached patch into Gnulib. This doesn't need any change to glibc: though it renames the Gnulib files that correspond to glibc, it does not change their contents.

It is an annoyance, though, that Gnulib-using apps now need another copy of the functions in question. How about publicizing that part of the glibc API, to avoid the duplication?

While looking into the above problem, I noticed a portability issue with platforms lacking getpwnam_r. Fixed in Gnulib in the 2nd attached patch.

And while looking into *that* problem, I noticed that the code needlessly saves and restores errno on platforms that have getpwnam_r. Fixed in Gnulib in the 3rd attached patch.

The last two patches should be ported back to glibc.

struct scratch_buffer depends on a GNU C extension:
assignment to an object changes its dynamic type.  It is not standard C.
  Standard C only allows one way to allocate untyped memory, and that is

That should not be a problem, as Gnulib code regularly breaks those standard-C rules when it comes to memory allocation. The old glob.c broke those rules too, and the change should not make us any worse in that department. The code should continue to work on all practical platforms that I know about; if you are aware of any realistic counterexamples please let us know.

Attachment: 0001-scratch_buffer-don-t-use-private-glibc-API.patch
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Attachment: 0002-glob-don-t-assume-getpwnam_r.patch
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Attachment: 0003-glob-don-t-save-and-restore-errno-unnecessarily.patch
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