tests: use valgrind where appropriate

Reported by Théophile Ranquet.

* cfg.mk (sc_at_parser_check): New.
* tests/c++.at: Fix use of AT_CHECK vs. AT_PARSER_CHECK.

cfg.mk

@@ -61,6 +61,18 @@ update-copyright: update-b4-copyright update-package-copyright-year
 update-copyright-env = \
   UPDATE_COPYRIGHT_FORCE=1 UPDATE_COPYRIGHT_USE_INTERVALS=1
 
+# At least for Mac OS X's grep, the order between . and [ in "[^.[]"
+# matters:
+# $ LC_ALL=fr_FR grep -nE '[^[.]' /dev/null
+# $ LC_ALL=C grep -nE '[^[.]' /dev/null
+# grep: invalid collating element or class
+# $ LC_ALL=fr_FR grep -nE '[^.[]' /dev/null
+# $ LC_ALL=C grep -nE '[^.[]' /dev/null
+sc_at_parser_check:
+	@prohibit='AT_PARSER_CHECK\(\[+[^.[]|AT_CHECK\(\[+\./'		\
+	halt='use AT_PARSER_CHECK for and only for generated parsers'	\
+	  $(_sc_search_regexp)
+
 exclude = \
   $(foreach a,$(1),$(eval $(subst $$,$$$$,exclude_file_name_regexp--sc_$(a))))
 $(call exclude,								\