[dpdk-dev] [PATCH v3] mk: filter duplicate configuration entries

[Christian Ehrhardt <christian.ehrhardt@canonical.com>]

*updates in v3*
- replace tac with sed '1!G;h;$!d' to avoid build time dependency

*updates in v2*
- move to .config target
- fix usage order of tac
- simplify inner section by only using awk (instead of awk+loop+bash+sed)

Due to the hierarchy and the demand to keep the base config showing all
options, some config keys end up multiple times in the .config file.

Due to the way the actual config is sourced only the last entry is
important. That can confuse people changing values in .config which
are then ignored.

A suggested solution was to filter for duplicates at the end of the
actual config step which is implemented here.

Signed-off-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>
---
 mk/rte.sdkconfig.mk | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mk/rte.sdkconfig.mk b/mk/rte.sdkconfig.mk
index a3acfe6..d031bf4 100644
--- a/mk/rte.sdkconfig.mk
+++ b/mk/rte.sdkconfig.mk
@@ -79,11 +79,17 @@ $(RTE_OUTPUT):
 ifdef NODOTCONF
 $(RTE_OUTPUT)/.config: ;
 else
+# Generate config from template, if there are duplicates keep only the last
 $(RTE_OUTPUT)/.config: $(RTE_CONFIG_TEMPLATE) FORCE | $(RTE_OUTPUT)
 	$(Q)if [ "$(RTE_CONFIG_TEMPLATE)" != "" -a -f "$(RTE_CONFIG_TEMPLATE)" ]; then \
 		$(CPP) -undef -P -x assembler-with-cpp \
 		-ffreestanding \
 		-o $(RTE_OUTPUT)/.config_tmp $(RTE_CONFIG_TEMPLATE) ; \
+		sed '1!G;h;$$!d' $(RTE_OUTPUT)/.config_tmp > $(RTE_OUTPUT)/.config_tmp_reverse ; \
+		awk --field-separator '=' '!/^#/ {if (!seen[$$1]) {print ($$0)}; seen[$$1]=1;} \
+			/^#/ {print($$0)}' $(RTE_OUTPUT)/.config_tmp_reverse \
+			| sed '1!G;h;$$!d' > $(RTE_OUTPUT)/.config_tmp ; \
+		rm $(RTE_OUTPUT)/.config_tmp_reverse ; \
 		if ! cmp -s $(RTE_OUTPUT)/.config_tmp $(RTE_OUTPUT)/.config; then \
 			cp $(RTE_OUTPUT)/.config_tmp $(RTE_OUTPUT)/.config ; \
 			cp $(RTE_OUTPUT)/.config_tmp $(RTE_OUTPUT)/.config.orig ; \
-- 
2.7.4