[Buildroot] [git commit branch/2018.02.x] Makefile: fix issue with printvars executing giant shell command

Peter Korsgaard peter at korsgaard.com
Fri Oct 5 11:31:25 UTC 2018


commit: https://git.buildroot.net/buildroot/commit/?id=afdf97ca768933b8deb5cc30e3b2fa61e55da9b5
branch: https://git.buildroot.net/buildroot/commit/?id=refs/heads/2018.02.x

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>
Tested-by: "Yann E. MORIN" <yann.morin.1998 at free.fr>
Acked-by: "Yann E. MORIN" <yann.morin.1998 at free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni at bootlin.com>
(cherry picked from commit b8d0aadc6d52733cfc914ba3cd6f506238bd19f7)
Signed-off-by: Peter Korsgaard <peter at korsgaard.com>
---
 Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 5fb26c9733..dc26099fd4 100644
--- a/Makefile
+++ b/Makefile
@@ -976,7 +976,8 @@ $(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)), \


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