Gorazd Rosbach

Important changes to forums and questions

All forums and questions are now archived. To start a new conversation or read the latest updates go to forums.mbed.com.

9 years ago.

Offline compiling printf does not print float values

Hi,

maybe this question is not directly mbed related, but anyway.

If I compile a printf statement offline (GCC arm-noneabi) I can't print out float values.

So:

float something 3.14; pc.printf("Something value %.2f \r\n",something);

will outout to a terminal only :

Something value

If I use online compiler, then everything works correctly.

Any answer to that?

1 Answer

Martin Kojtal
9 years ago.

Does your makefile/cmake or whatever you use for building contain support for floats ? If you are using newlib, you should look at this command: -u _printf_float -specs=nano.specs

If you export gcc make project from the online compiler, it should contain those flags, use nano plus add printf float support, same can be applied to scanf.

Hi,

I'll try it in the afternoon. I use exported gcc make project from the online compiler. I allways create a project online, then I export it to offline (GNU/GCC). After the code is done, I copy/paste the source to online compiler just to have another copy of it (in case of data loss on my computers).

RGDS

Hi, I checked the default Makefile, the above specified command is by default commented out, so I'll try to uncomment and recompile and try.

LD_FLAGS = $(CPU) -Wl,--gc-sections --specs=nano.specs -Wl,--wrap,main -Wl,-Map=$(PROJECT).map,--cref
#LD_FLAGS += -u _printf_float -u _scanf_float
LD_SYS_LIBS = -lstdc++ -lsupc++ -lm -lc -lgcc -lnosys

Hi, I found some time to check if this works, but sadly it does not.

This is the makefile (I uncomented the LD FLAGS for printf float) but with no results.

# This file was automagically generated by mbed.org. For more information, 
# see http://mbed.org/handbook/Exporting-to-GCC-ARM-Embedded

GCC_BIN = 
PROJECT = Float_printtest
OBJECTS = ./main.o 
SYS_OBJECTS = ./mbed/TARGET_KL25Z/TOOLCHAIN_GCC_ARM/board.o ./mbed/TARGET_KL25Z/TOOLCHAIN_GCC_ARM/cmsis_nvic.o ./mbed/TARGET_KL25Z/TOOLCHAIN_GCC_ARM/mbed_overrides.o ./mbed/TARGET_KL25Z/TOOLCHAIN_GCC_ARM/retarget.o ./mbed/TARGET_KL25Z/TOOLCHAIN_GCC_ARM/startup_MKL25Z4.o ./mbed/TARGET_KL25Z/TOOLCHAIN_GCC_ARM/system_MKL25Z4.o 
INCLUDE_PATHS = -I. -I./mbed -I./mbed/TARGET_KL25Z -I./mbed/TARGET_KL25Z/TARGET_Freescale -I./mbed/TARGET_KL25Z/TARGET_Freescale/TARGET_KLXX -I./mbed/TARGET_KL25Z/TARGET_Freescale/TARGET_KLXX/TARGET_KL25Z -I./mbed/TARGET_KL25Z/TOOLCHAIN_GCC_ARM 
LIBRARY_PATHS = -L./mbed/TARGET_KL25Z/TOOLCHAIN_GCC_ARM 
LIBRARIES = -lmbed 
LINKER_SCRIPT = ./mbed/TARGET_KL25Z/TOOLCHAIN_GCC_ARM/MKL25Z4.ld

############################################################################### 
AS      = $(GCC_BIN)arm-none-eabi-as
CC      = $(GCC_BIN)arm-none-eabi-gcc
CPP     = $(GCC_BIN)arm-none-eabi-g++
LD      = $(GCC_BIN)arm-none-eabi-gcc
OBJCOPY = $(GCC_BIN)arm-none-eabi-objcopy
OBJDUMP = $(GCC_BIN)arm-none-eabi-objdump
SIZE    = $(GCC_BIN)arm-none-eabi-size 


CPU = -mcpu=cortex-m0plus -mthumb 
CC_FLAGS = $(CPU) -c -g -fno-common -fmessage-length=0 -Wall -Wextra -fno-exceptions -ffunction-sections -fdata-sections -fomit-frame-pointer -MMD -MP
CC_SYMBOLS = -DTARGET_FF_ARDUINO -DTOOLCHAIN_GCC_ARM -DTARGET_KLXX -DTARGET_KL25Z -DTARGET_CORTEX_M -DTARGET_M0P -DTARGET_Freescale -DMBED_BUILD_TIMESTAMP=1449175537.46 -D__CORTEX_M0PLUS -DTOOLCHAIN_GCC -D__MBED__=1 -DARM_MATH_CM0PLUS 

LD_FLAGS = $(CPU) -Wl,--gc-sections --specs=nano.specs -Wl,--wrap,main -Wl,-Map=$(PROJECT).map,--cref
LD_FLAGS += -u _printf_float -u _scanf_float
LD_SYS_LIBS = -lstdc++ -lsupc++ -lm -lc -lgcc -lnosys


ifeq ($(DEBUG), 1)
  CC_FLAGS += -DDEBUG -O0
else
  CC_FLAGS += -DNDEBUG -Os
endif

.PHONY: all clean lst size

all: $(PROJECT).bin $(PROJECT).hex size


clean:
	rm -f $(PROJECT).bin $(PROJECT).elf $(PROJECT).hex $(PROJECT).map $(PROJECT).lst $(OBJECTS) $(DEPS)


.asm.o:
	$(CC) $(CPU) -c -x assembler-with-cpp -o $@ $<
.s.o:
	$(CC) $(CPU) -c -x assembler-with-cpp -o $@ $<
.S.o:
	$(CC) $(CPU) -c -x assembler-with-cpp -o $@ $<

.c.o:
	$(CC)  $(CC_FLAGS) $(CC_SYMBOLS) -std=gnu99   $(INCLUDE_PATHS) -o $@ $<

.cpp.o:
	$(CPP) $(CC_FLAGS) $(CC_SYMBOLS) -std=gnu++98 -fno-rtti $(INCLUDE_PATHS) -o $@ $<



$(PROJECT).elf: $(OBJECTS) $(SYS_OBJECTS)
	$(LD) $(LD_FLAGS) -T$(LINKER_SCRIPT) $(LIBRARY_PATHS) -o $@ $^ $(LIBRARIES) $(LD_SYS_LIBS) $(LIBRARIES) $(LD_SYS_LIBS)


$(PROJECT).bin: $(PROJECT).elf
	$(OBJCOPY) -O binary $< $@

$(PROJECT).hex: $(PROJECT).elf
	@$(OBJCOPY) -O ihex $< $@

$(PROJECT).lst: $(PROJECT).elf
	@$(OBJDUMP) -Sdh $< > $@

lst: $(PROJECT).lst

size: $(PROJECT).elf
	$(SIZE) $(PROJECT).elf

DEPS = $(OBJECTS:.o=.d) $(SYS_OBJECTS:.o=.d)
-include $(DEPS)

install:
	cp $(PROJECT).bin /media/gorazd/MBED1/$(PROJECT).bin
posted by Gorazd Rosbach 03 Dec 2015