libc: Recompile newlib to enable float & long double i/o in printf/scanf

Enabled by default, set PRINTF_SCANF_FLOAT_SUPPORT=0 in local.mk/Makefile to disable

newlib-xtensa revision ae10be3

Configure/compile steps:

../configure --with-newlib --enable-multilib
--disable-newlib-io-c99-formats --enable-newlib-supplied-syscalls --enable-target-optspace --program-transform-name="s&^&xtensa-lx106-elf-&" --disable-option-checking --with-target-subdir=xtensa-lx106-elf
--target=xtensa-lx106-elf --prefix=/home/gus/dev/esp/rtos/open-rtos/libc/ --enable-newlib-nano-malloc --enable-newlib-nano-formatted-io --enable-newlib-reent-small --prefix=path_to/esp-open-rtos/libc

CROSS_CFLAGS="-DSIGNAL_PROVIDED -DABORT_PROVIDED" make
make install

Closes #95

common.mk

@@ -48,6 +48,13 @@ ESPTOOL ?= esptool.py
 ESPPORT ?= /dev/ttyUSB0
 ESPBAUD ?= 115200
 
+# set this to 0 if you don't need floating point support in printf/scanf
+# this will save approx 14.5KB flash space and 448 bytes of statically allocated
+# data RAM
+#
+# NB: Setting the value to 0 requires a recent esptool.py (Feb 2016 / commit ebf02c9)
+PRINTF_SCANF_FLOAT_SUPPORT ?= 1
+
 # Set OTA to 1 to build an image that supports rBoot OTA bootloader
 #
 # Currently only works with 16mbit or more flash sizes, with 8mbit
@@ -109,7 +116,7 @@ CXXFLAGS	?= $(C_CXX_FLAGS) -fno-exceptions -fno-rtti $(EXTRA_CXXFLAGS)
 # these aren't technically preprocesor args, but used by all 3 of C, C++, assembler
 CPPFLAGS	+= -mlongcalls -mtext-section-literals
 
-LDFLAGS		= -nostdlib -Wl,--no-check-sections -L$(BUILD_DIR)sdklib -L$(ROOT)lib -u $(ENTRY_SYMBOL) -Wl,-static -Wl,-Map=$(BUILD_DIR)$(PROGRAM).map  $(EXTRA_LDFLAGS)
+LDFLAGS		= -nostdlib -Wl,--no-check-sections -L$(BUILD_DIR)sdklib -L$(ROOT)lib -u $(ENTRY_SYMBOL) -Wl,-static -Wl,-Map=$(BUILD_DIR)$(PROGRAM).map $(EXTRA_LDFLAGS)
 
 ifeq ($(SPLIT_SECTIONS),1)
   C_CXX_FLAGS += -ffunction-sections -fdata-sections
@@ -202,6 +209,9 @@ INC_DIRS      = $(PROGRAM_DIR) $(PROGRAM_DIR)include $(ROOT)include
 ifeq ($(OWN_LIBC),1)
     INC_DIRS += $(ROOT)libc/xtensa-lx106-elf/include
     LDFLAGS += -L$(ROOT)libc/xtensa-lx106-elf/lib
+   ifeq ($(PRINTF_SCANF_FLOAT_SUPPORT),1)
+     LDFLAGS += -u _printf_float -u _scanf_float
+   endif
 endif
 
 ifeq ("$(V)","1")

libc/xtensa-lx106-elf/include/config.h

@@ -0,0 +1,43 @@
+#ifndef __SYS_CONFIG_H__
+#define __SYS_CONFIG_H__
+
+#include <machine/ieeefp.h>  /* floating point macros */
+#include <sys/features.h>	/* POSIX defs */
+
+/*************************************************************************
+ esp8266-specific xtensa stuff
+ *************************************************************************/
+
+#ifndef _REENT_SMALL
+#define _REENT_SMALL
+#endif
+
+/* esp8266 hardware FIFO buffers are 128 bytes */
+#define __BUFSIZ__ 128
+
+/*************************************************************************
+ end of esp8266-specific stuff
+ *************************************************************************/
+
+#ifndef __EXPORT
+#define __EXPORT
+#endif
+
+#ifndef __IMPORT
+#define __IMPORT
+#endif
+
+/* Define return type of read/write routines.  In POSIX, the return type
+   for read()/write() is "ssize_t" but legacy newlib code has been using
+   "int" for some time.  If not specified, "int" is defaulted.  */
+#ifndef _READ_WRITE_RETURN_TYPE
+#define _READ_WRITE_RETURN_TYPE int
+#endif
+/* Define `count' parameter of read/write routines.  In POSIX, the `count'
+   parameter is "size_t" but legacy newlib code has been using "int" for some
+   time.  If not specified, "int" is defaulted.  */
+#ifndef _READ_WRITE_BUFSIZE_TYPE
+#define _READ_WRITE_BUFSIZE_TYPE int
+#endif
+
+#endif /* __SYS_CONFIG_H__ */