Make string0 use configurable

Author: tannewt

ports/espressif/mpconfigport.mk

@@ -59,6 +59,8 @@ CIRCUITPY_PORT_SERIAL = 1
 
 CIRCUITPY_LIB_TLSF = 0
 
+CIRCUITPY_LIBC_STRING0 = 0
+
 # These modules are implemented in ports/<port>/common-hal:
 CIRCUITPY__EVE ?= 1
 CIRCUITPY_ALARM ?= 1

py/circuitpy_defns.mk

@@ -1003,6 +1003,10 @@ SRC_CIRCUITPY_COMMON = \
 	shared/runtime/stdout_helpers.c \
 	shared/runtime/sys_stdio_mphal.c
 
+ifeq ($(CIRCUITPY_LIBC_STRING0),1)
+SRC_CIRCUITPY_COMMON += shared/libc/string0.c
+endif
+
 ifeq ($(CIRCUITPY_QRIO),1)
 SRC_CIRCUITPY_COMMON += lib/quirc/lib/decode.c lib/quirc/lib/identify.c lib/quirc/lib/quirc.c lib/quirc/lib/version_db.c
 $(BUILD)/lib/quirc/lib/%.o: CFLAGS += -Wno-type-limits -Wno-shadow -Wno-sign-compare -include shared-module/qrio/quirc_alloc.h

py/circuitpy_mpconfig.mk

@@ -66,6 +66,11 @@ CIRCUITPY_MESSAGE_COMPRESSION_LEVEL ?= 9
 # implementation of TLSF, which can be used instead by setting CIRCUITPY_LIB_TLSF=0.
 CIRCUITPY_LIB_TLSF ?= 1
 
+# By default, use our copy of string0 (memcpy and friends) because it is optimized. Some vendor SDKs
+# or ROMs may provide their own implementation of string0, which can be used instead by setting
+# CIRCUITPY_LIBC_STRING0=0.
+CIRCUITPY_LIBC_STRING0 ?= 1
+
 # Reduce the size of in-flash properties. Requires support in the .ld linker
 # file, so not enabled by default.
 CIRCUITPY_OPTIMIZE_PROPERTY_FLASH_SIZE ?= 0