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Makefile: fix issue with printvars executing giant shell command

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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@impinj.com>
Tested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
This commit is contained in:
Trent Piepho 2018-09-17 11:10:54 -07:00 committed by Thomas Petazzoni
parent ca5ae83ccb
commit b8d0aadc6d
1 changed files with 2 additions and 1 deletions
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3
Makefile
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@ -988,7 +988,8 @@ $(BUILD_DIR)/.br2-external.in: $(BUILD_DIR)
# displayed.
.PHONY: printvars
printvars:
@:$(foreach V, \
@:
$(foreach V, \
$(sort $(if $(VARS),$(filter $(VARS),$(.VARIABLES)),$(.VARIABLES))), \
$(if $(filter-out environment% default automatic, \
$(origin $V)), \