Bugfix/fix redundant compiler flags (#658)

* Improved GCC compiler flags in ARM, OS, and test builds. Removed redundant flags, and made them consistent across various builds.

* Fixed redundant redeclaration of various functions detected by change in compiler flags.

* Fixed string truncation warning in bip-init detected by change in compiler flags.

* Fixed some set-but-not-used variables by creating dummy functions instead of using macros.

ports/at91sam7s/CMakeLists.txt

@@ -191,9 +191,20 @@ target_compile_definitions(${EXECUTABLE} PRIVATE
     -DBACAPP_MINIMAL
 )
 
-# inhibit pedantic warnings
 target_compile_options(${EXECUTABLE} PRIVATE
-    -Wall
+    -Wall -Wextra -pedantic
+    -Wfloat-equal -Wconversion -Wredundant-decls 
+    -Wswitch-default
+    # don't warn about conversion, sign, compares, long long and attributes
+    # since they are common in embedded
+    -Wno-sign-conversion 
+    -Wno-conversion
+    -Wno-sign-compare 
+    -Wno-long-long
+    -Wno-attributes
+    # don't warn about implicit fallthrough since it is common in network protocols
+    -Wno-implicit-fallthrough
+    # the older Atmel SDK does not meet coding guidelines
     -Wno-comment
     -Wno-missing-braces
     -Wno-unused-variable

ports/at91sam7s/Makefile

@@ -38,8 +38,22 @@ CFLAGS = -fno-common $(INCLUDES) $(BACNET_FLAGS) -g
 CFLAGS += -mno-thumb-interwork
 # dead code removal
 CFLAGS += -fdata-sections -ffunction-sections
-# warning control
-CFLAGS += -Wall
+
+# enable all relevant warnings that find bugs
+WARNING_ALL := -Wall -Wextra -Wfloat-equal -Wconversion
+WARNING_ALL += -Wredundant-decls -Wswitch-default -pedantic
+# don't warn about conversion, sign, compares, long long and attributes
+# since they are common in embedded
+WARNING_ALL += -Wno-sign-conversion -Wno-conversion -Wno-sign-compare
+WARNING_ALL += -Wno-long-long -Wno-attributes
+# don't warn about implicit fallthrough since it's common in network protocols
+WARNING_ALL += -Wno-implicit-fallthrough
+# the older Atmel SDK does not meet coding guidelines
+WARNING_ALL += -Wno-comment -Wno-missing-braces
+WARNING_ALL += -Wno-unused-variable -Wno-char-subscripts
+#WARNING_ALL += -Werror
+CFLAGS += $(WARNING_ALL)
+
 CFLAGS += -Wno-char-subscripts
 
 LIBRARY = lib$(TARGET).a