Bug#1010121: libx11: FTCBFS: cannot run test program while cross compiling

[Daniel Schepler]

Source: libx11
Version: 2:1.7.5-1
Severity: wishlist

While doing a test bootstrap of i386 from amd64, I ran into an error
trying to cross build libx11:

...
checking for xproto >= 7.0.25 xextproto xtrans xcb >= 1.11.1 kbproto
inputproto... yes
checking whether malloc(0) returns NULL... configure: error: in
`/home/tmpbuilder/cross-i386/libx11/libx11-1.7.5/build':
configure: error: cannot run test program while cross compiling
See `config.log' for more details
...

(This came up as a Build-Depends of groff, while trying to
cross-compile enough packages to make debhelper installable.)
--
Daniel Schepler

[Helmut Grohne]

Control: tags -1 + moreinfo

Hi Daniel,

On Sun, Apr 24, 2022 at 02:48:12PM -0700, Daniel Schepler wrote:
> While doing a test bootstrap of i386 from amd64, I ran into an error
> trying to cross build libx11:
>
> ...
> checking for xproto >= 7.0.25 xextproto xtrans xcb >= 1.11.1 kbproto
> inputproto... yes
> checking whether malloc(0) returns NULL... configure: error: in
> `/home/tmpbuilder/cross-i386/libx11/libx11-1.7.5/build':
> configure: error: cannot run test program while cross compiling
> See `config.log' for more details
> ...

Supposedly, this has been addressed in cross-config, which supplies the
relevant cache variable xorg_cv_malloc0_returns_null. sbuild
automatically enables this cache. Accordingly, libx11 cross builds
successfully in QA: https://crossqa.debian.net/src/libx11.

Do you see any actionable aspect in this bug or can we close it? Adding
the cache variable to each and every X11 library does not seem like an
effective solution to me.

I note that the cache is wrong on musl-any-any.

Helmut