Set C99 as standard

.pre-commit-config.yaml

@@ -25,4 +25,4 @@ repos:
     rev: v1.3.5
     hooks:
     - id: cppcheck
-      args: ["--enable=all", "--suppress=missingIncludeSystem", "--language=c"]
+      args: ["--enable=all", "--suppress=missingIncludeSystem", "--language=c", "--std=c99"]

require.Makefile

@@ -69,6 +69,8 @@ HEADERS += $(APPSRC)/require.h
 # We need to find the Linux link.h before the EPICS link.h
 USR_INCLUDES_Linux=-idirafter $(EPICS_BASE)/include
 
+USR_CFLAGS += --std=c99
+
 # ESS require doesn't use T_A, because Linux should handle linux as "1"
 # instead of its name. ESS require can handle them within the EPICS
 # IOC shell internally.