tree 0d9bd6f320b72baa84af7524a36c432071a4319d
parent 3ddf1d8a82608b0a8106b3ac91be870450125f1e
author Ahmad Fatoum <a.fatoum@pengutronix.de> 1710274989 +0100
committer Ahmad Fatoum <a.fatoum@pengutronix.de> 1712657822 +0200

feat(build): redirect stdin to nul during toolchain detection

It's common for Makefiles to use variables like CC, AS or LD instead of
hardcoding the name of binaries. These can be defined by the user to
use a differnet toolchain or even as a crutch to enable cross-compilation.

In TF-A, this is not needed, as support for cross-compilation is baked
in via the CROSS_COMPILE option. TF-A still defined AS for its internal
use, but unlike most other projects, the default was setting it to the C
compiler. Overriding it wasn't possible from the environment though,
only as a make argument, so this didn't cause much issue.

With commit cc277de81692 ("build: refactor toolchain detection"), AS can
now also be set from the environment. This breaks any scripts that
supply make with a cross environment that sets AS to an assembler.

Doing so was without effect before, but now leads to a quite ugly failure
mode: As TF-A now tries to detect the toolchain, it will call AS with the
option -v, which for GNU as(1) prints the version, but doesn't exit.

Thus, as(1) will continue waiting on stdin input and the build hangs
without much indication what's wrong.

Avoid this failure mode by ensuring any tool that attempts to read stdin
during toolchain detection will immediately get EOF and exit, leading to
an error message later on instead of the build hang.

Change-Id: I79a84961f5a69250292caa7f9e879a65be4bd9f2
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>