[Buildroot] [PATCH v2] Fix issue with printvars executing giant shell command

[Thomas Petazzoni]

Hello,

On Mon, 17 Sep 2018 11:10:54 -0700, Trent Piepho wrote:
> The underlying problem is that $(foreach V,1 2 3,) does not evaluate to
> an empty string.  It evaluates to "  ", three empty strings separated by
> whitespace.
> 
> A construct of this format, with a giant list in the foreach, is part of
> the printvars command.  This means that "@:$(foreach ....)", which is
> intended to expand to a null command, in fact expands to "@:       "
> with a great deal of whitespace.  Make chooses to execute this command
> with:
>     execve("/bin/sh", ["/bin/sh", "-c", ":       "]
> 
> But with far more whitespace.  So much that it can exceed shell command
> line length limits.
> 
> This solution is to move the foreach to another step in the recipe.  The
> "@:" is retained as the first line so the recipe is not Empty, which
> would cause a change in make behavior when make builds the target.  The
> 2nd line, all whitespace, will be skipped by make.
> 
> Signed-off-by: Trent Piepho <tpiepho at impinj.com>
> ---
>  Makefile | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

Applied to master, thanks.

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com