There are two methods to include static library, adding it into arch library and adding it as a new library.

Makefile or Make.defs in arch can include static libraries for specific architectures as mentioned below. As a convention, the specified static library is added to libarch.a in the final build.

VPATH += <LIB_PATH>
EXTRA_LIBS += <LIB_PATH>/<LIB_NAME>.a

The LIB_PATH should be a relative path from os/arch/arm/src.

For example,

VPATH += chip/abc
EXTRA_LIBS += chip/abc/libnew.a

This allows adding a static library from within the Makefile located at os/arch/arm/src folder. The specified library libnew.a will be merged under libarch.a.

$(OUTBIN_DIR)/tinyara$(EXEEXT): $(HEAD_OBJ) board/libboard$(LIBEXT)
	$(Q) echo "LD: tinyara"
	$(Q) $(LD) --entry=__start $(LDFLAGS) $(LIBPATHS) $(EXTRA_LIBPATHS) \
		-o $(TINYARA) $(HEAD_OBJ) $(EXTRA_OBJS) \
		--start-group $(LDLIBS) $(EXTRA_LIBS) $(LIBGCC) --end-group -Map $(TOPDIR)/../build/output/bin/tinyara.map

TizenRT also allows including a static library as a separate entity, without merging it to an existing library. The following steps describe how to include a static library:

1. Add the static library in Libtargets.mk.

   $(LIBRARIES_DIR)$(DELIM)<LIB_NAME>$(LIBEXT): <LIB_PATH>$(DELIM)<LIB_NAME>$(LIBEXT)
   	$(Q) install <LIB_PATH>$(DELIM)<LIB_NAME>$(LIBEXT) $(LIBRARIES_DIR)$(DELIM)<LIB_NAME>$(LIBEXT)
   

2. Add the static library in FlatLibs.mk, ProtectedLibs.mk and KernelLibs.mk.

   For kernel library,

   TINYARALIBS += $(LIBRARIES_DIR)$(DELIM)<LIB_NAME>$(LIBEXT)
   

   For user library,

   USERLIBS += $(LIBRARIES_DIR)$(DELIM)<LIB_NAME>$(LIBEXT)
   

   In flat build, there is no difference between TINYARALIBS and USERLIBS.
   But in protected build and kernel build, TizenRT splits kernel space and user space. So, new static library should be included at appropriate space.

The LIB_PATH should be a relative path from os.