core/printvars: allow dumping a set of variables
Dumping our 176164 variables can take quite some time (~12s here). What
takes the most time is sorting the variables (~9s), followed by the
parsing of our Makefiles (~3s), with the actual printing in the noise.
However, sometimes only one or a few variables are needed. For example,
one may want to retrieve the Linux build dir from a post-build hook (to
get the Linux' actual .config after our fixups and check for various
features).
Add the possibility to only dump the variables listed in $(VAR) which
must be passed as a make argument, like so:
$ make -s printvars VARS="LINUX_DIR TOPDIR O"
LINUX_DIR=/home/ymorin/dev/buildroot/O/build/linux-4.3 ($(BUILD_DIR)/$(LINUX_BASE_NAME))
O=/home/ymorin/dev/buildroot/O/. (/home/ymorin/dev/buildroot/O/.)
TOPDIR=/home/ymorin/dev/buildroot/buildroot (/home/ymorin/dev/buildroot/buildroot)
It is also possible to use make-appterns, like:
$ make -s printvars VARS="BUSYBOX_%"
This is much faster (the time is just about the time it takes to parse
our Makefiles, 3s here) and easier to parse.
[Thomas: improve comment above the printvars target.]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
diff --git a/Makefile b/Makefile
index 9950a26..641aeff 100644
--- a/Makefile
+++ b/Makefile
@@ -823,10 +823,13 @@
$(Q)$(TOPDIR)/support/scripts/mkmakefile $(TOPDIR) $(O)
endif
-# printvars prints all the variables currently defined in our Makefiles
+# printvars prints all the variables currently defined in our
+# Makefiles. Alternatively, if a non-empty VARS variable is passed,
+# only the variables matching the make pattern passed in VARS are
+# displayed.
printvars:
@$(foreach V, \
- $(sort $(.VARIABLES)), \
+ $(sort $(if $(VARS),$(filter $(VARS),$(.VARIABLES)),$(.VARIABLES))), \
$(if $(filter-out environment% default automatic, \
$(origin $V)), \
$(info $V=$($V) ($(value $V)))))
