bin_PROGRAMS += vppapigen
-BUILT_SOURCES += tools/vppapigen/gram.h
+# We cannot rely on BUILT_SOURCES here as other built sources are relying
+# on vppapigen, so make can start compiling lex.c before gram.h is created.
+# This way we introduce new dependency by running C preprocessor.
-tools/vppapigen/gram.h: tools/vppapigen/gram.y
- $(YACC) -d @srcdir@/tools/vppapigen/gram.y
- mv y.tab.h tools/vppapigen/gram.h
- rm y.tab.c
+tools/vppapigen/lex_e.c: tools/vppapigen/lex.c tools/vppapigen/gram.y
+ @$(YACC) -d @srcdir@/tools/vppapigen/gram.y
+ @mv y.tab.h tools/vppapigen/gram.h
+ @rm y.tab.c
+ @$(CC) -I. -E -o $@ $<
-vppapigen_SOURCES = tools/vppapigen/gram.y tools/vppapigen/lex.c tools/vppapigen/node.c
+vppapigen_SOURCES = tools/vppapigen/gram.y tools/vppapigen/lex_e.c tools/vppapigen/node.c
vppapigen_LDADD = libvppinfra.la
vppapigen_LDFLAGS = -static