[PATCH 2/4] tools lib traceevent: Robustify do_generate_dynamic_list_file

[David Carrillo-Cisneros <davidcc@google.com>]

The dynamic-list-file used to export dynamic symbols introduced in

commit e3d09ec8126f ("tools lib traceevent: Export dynamic symbols
used by traceevent plugins")

is generated without any sort of error checking.

I experienced problems due to an old version of nm (v 0.158) that outputs
in a format distinct from the assumed by the script.

Robustify this by enforcing that the second column in the symbol output
is an "U" (Undefined) as it should be since we are calling $(NM) -u ...
and print an error message otherwise.

Signed-off-by: David Carrillo-Cisneros <davidcc@google.com>
---
 tools/lib/traceevent/Makefile | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/tools/lib/traceevent/Makefile b/tools/lib/traceevent/Makefile
index 2616c66e10c1..1b6e146429d0 100644
--- a/tools/lib/traceevent/Makefile
+++ b/tools/lib/traceevent/Makefile
@@ -257,10 +257,15 @@ define do_install_plugins
 endef
 
 define do_generate_dynamic_list_file
-	(echo '{';							\
-	$(NM) -u -D $1 | awk 'NF>1 {print "\t"$$2";"}' | sort -u;	\
-	echo '};';							\
-	) > $2
+	symbol_type=`$(NM) -u -D $1 | awk 'NF>1 {print $$1}' | sort -u`;\
+	if [ "$$symbol_type" == "U" ];then				\
+		(echo '{';						\
+		$(NM) -u -D $1 | awk 'NF>1 {print "\t"$$2";"}' | sort -u;\
+		echo '};';						\
+		) > $2;							\
+	else								\
+		(echo Either missing one of [$1] or bad version of $(NM)) 1>&2;\
+	fi
 endef
 
 install_lib: all_cmd install_plugins
-- 
2.11.0.483.g087da7b7c-goog