+# AT_CHECK_BISON_PERCENT_FLAGS(GRAMMAR_OPTIONS, FLAGS, EXPECTED-FILES-SORTED)
+# ---------------------------------------------------------------------------
+AT_DEFINE([AT_CHECK_BISON_PERCENT_FLAGS],
+[AT_SETUP([Output files: $1.])
+AT_DATA([foo.yy],
+[[$1
+%defines
+%verbose
+%%
+foo: {}
+]])
+rm -rf $3
+AT_CHECK([bison foo.yy $2], 0, ignore, ignore)
+AT_CHECK([ls $3 | sort | tr '\n' ' ' | sed 's/.$//g'], 0, [$3])
+rm -f $3
+AT_CLEANUP
+])
+
+# Check priorities of extension control.
+AT_CHECK_BISON_PERCENT_FLAGS(
+[],
+[],
+[foo.output foo.tab.cc foo.tab.hh])
+AT_CHECK_BISON_PERCENT_FLAGS(
+[],
+[-o foo.c],
+[foo.c foo.h foo.output])
+AT_CHECK_BISON_PERCENT_FLAGS(
+[%source_extension ".cpp"] [%header_extension ".hhh"],
+[],
+[foo.output foo.tab.cpp foo.tab.hhh])
+AT_CHECK_BISON_PERCENT_FLAGS(
+[%source_extension ".cc"] [%header_extension ".hh"],
+[-o foo.c],
+[foo.c foo.h foo.output])
+