dietlibc fails to cross build from source. The ultimate failure arises
when it tries to execute diet for the host architecture.

So I looked and what I found was very confusing. There are lots of
problems. Let me start by quoting the dietlibc FAQ[1]:

| Q: Do you have cross compiling support?
| A: Yes.  Just type something like "make ARCH=arm CROSS=arm-linux- all".
|    For arm, alpha, mips, ppc, sparc and i386, shortcuts exist.  You can
|    also use "make arm", for example.  You still use the same "diet"
|    program as for normal compilation, but you can then say
|
|      $ diet sparc-linux-gcc -pipe -g -o t t.c
|
|    Programs using autoconf can be configured like this:
|
|      $ CC="diet sparc-linux-gcc" ./configure --disable-nls

Unfortunately, the packaging gets this completely wrong. The FAQ says
that you should set ARCH, but the packaging sets MYARCH. In GNU
terminology, ARCH is the host architecture and MYARCH is the build
architecture. Thus the packaging confuses build and host here.

Next up, it doesn't pass CROSS. The value should be
"${DEB_HOST_GNU_TYPE}-".

The upstream Makefile expects to be in control of the CC variable.
Unfortunately, most other Makefiles expect not to be in control, so
dh_auto_build passes CC as a command line variable now. This renders
upstream statements such as

    CC+=-D__dietlibc__

ineffective (and it should be using CFLAGS anyway). I'm afraid, we
cannot use dh_auto_build here without expecting breakage.

Then the build wants to run "bin-${MYARCH}/diet". But it doesn't build
that. For cross compiling, one needs another build pass where ARCH and
CROSS are not set.

Finally, when using dietlibc, one wants the diet program to come from
the build architecture and the library for the host architecture. The
packaging however stuffs both into the same binary package. The typical
fix is to split dietlibc-dev into another package dietlibc-dev-bin. Then
move the diet program there and move it into an architecture-independent
path. Mark dietlibc-dev-bin Multi-Arch: foreign and have dietlibc-dev
depend on it. You can turn the original architecture-dependent paths
into symlinks for backwards-compatibility.

I tried implementing what I sketched here, but it turned out I was
producing more and more stranger and stranger errors (presumably,
because I don't understand the packaging well enough). Thus I only write
down what I know and hope that you can fix at least some aspects. I'm
happy to help.

Unfortunately, dietlibc suddenly became part of the bootstrap problem
when gdbm started Build-Depending on it.

Helmut

[1] https://www.fefe.de/dietlibc/FAQ.txt

We believe that the bug you reported is fixed in the latest version of
gdbm, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 889080@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Gianfranco Costamagna <locutusofborg@debian.org> (supplier of updated gdbm package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Sat, 10 Feb 2018 13:45:31 +0100
Source: gdbm
Binary: libgdbm5 gdbm-l10n libgdbm-dev gdbmtool libgdbm-compat4 libgdbm-compat-dev
Architecture: source
Version: 1.14.1-3
Distribution: unstable
Urgency: medium
Maintainer: Dmitry Bogatov <KAction@gnu.org>
Changed-By: Gianfranco Costamagna <locutusofborg@debian.org>
Description:
 gdbm-l10n  - GNU dbm database routines (translation files)
 gdbmtool   - GNU dbm database routines (command line tools)
 libgdbm-compat-dev - GNU dbm database routines (legacy support development files)
 libgdbm-compat4 - GNU dbm database routines (legacy support runtime version)
 libgdbm-dev - GNU dbm database routines (development files)
 libgdbm5   - GNU dbm database routines (runtime version)
Closes: 889057 889080 889107 889474
Changes:
 gdbm (1.14.1-3) unstable; urgency=medium
 .
   [ Helmut Grohne ]
   * Add pkg.gdbm.nodietlibc build profile. (Closes: #889474)
 .
   [ Gianfranco Costamagna ]
   * Team upload
   * Fixup typo in breaks, leading to upgrade failures (Closes: #889107)
     Thanks <anbe> for the useful bug report!
   * Remove ia64 from dietlibc (Closes: #889057)
   * Disable for now dietlibc build, it makes bootstrap really problematic,
     and needs some extra work (Closes: #889080).
Checksums-Sha1:
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 d77215e7feae11c00e30a82af88094000c9fedc0 25932 gdbm_1.14.1-3.debian.tar.xz
 7d73427cf0e16843d461e5725eaf398914170bd4 6742 gdbm_1.14.1-3_source.buildinfo
Checksums-Sha256:
 f74a56e78dbc6308118e272a53bbb5acc5ec1c527510a41c6c9e9ec5f8361083 2122 gdbm_1.14.1-3.dsc
 5d499c3cc64c85636f5cf3cdba6a2dea17d86a6527b23ebf374e29603f79db49 25932 gdbm_1.14.1-3.debian.tar.xz
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 1dc2100d0f557fa577a0bdab78c7eba5 25932 libs important gdbm_1.14.1-3.debian.tar.xz
 4c6692759c2dc68dd981e6cefa8d2839 6742 libs important gdbm_1.14.1-3_source.buildinfo
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Whilst bootstrapping gdbm no longer requires bootstrapping dietlibc,
this does not change whether dietlibc FTCBFS, which is what this bug is
about. It is obviously less important now though.

Regards,
James