about the link error with arm-none-eabi on the eclipse environment.

[neweins]

Hello all

I'm struggling with link errors, "undefined referencce atan2" as well as all math library. I still dont know why it is occurred these errors. I configured the eclipse compile environment with the gnu arm tool using your doc, application note ver1.2. May you help me?

[Ole Morten]

As far as I can see, this just works out of the box. Please see the attached example, that should compile directly if you put it in the Board/nrf6310/ folder, both with SDK version 4.3.0 and 4.4.0. If you still struggle, could you please upload your complete project, including any Makefiles and linker scripts?

math-lib.zip

[Markus Roppelt]

I can compile the attached math-lib.zip. However if I change the the argument to a variable I get following error.

main.c:(.text.startup+0x5a): undefined reference to `atan2'
collect2.exe: error: ld returned 1 exit status
make: *** [_build/template_project_gcc_s110_xxaa.out] Fehler 1

My main is:

int main(void)
{	
	uint8_t idx = 0;
	double d_idx = 0.0;
	uint8_t buffer[20];
	simple_uart_config(0, 17, 0, 16, false);
	simple_uart_putstring((uint8_t *)"Start\r\n");
	nrf_gpio_range_cfg_output(8, 15);
	
	while (true)
    {
		idx++;
		d_idx = (double) idx;
		float result = atan2(1.0, d_idx);
		sprintf((char *)buffer, "%f\r\n", result);
		simple_uart_putstring(buffer);
		nrf_delay_us(100000);
    }
}

How can I build this?

Greetings Markus

[Ole Morten]

You're right, I see the same when I tried this modification. To make it work, I had to add -lm to the linking command line. Beware that the place in the line actually matters, but things seemed to work when I put it right before the -o parameter in the final linking: $(CC) $(LDFLAGS) $(C_OBJECTS) $(ASSEMBLER_OBJECTS) $(LIBRARIES) -lm -o $(OUTPUT_BINARY_DIRECTORY)/$(OUTPUT_FILENAME).out

[maxpaynner]

I had this same problem.

The solution was:

1- Link with GCC instead of LD (some guys recommend this, dunno where I read it, but seems to work). In your makefile replace

LD       		:= "$(GNU_INSTALL_ROOT)/bin/$(GNU_PREFIX)-ld"

With

LD       		:= "$(GNU_INSTALL_ROOT)/bin/$(GNU_PREFIX)-gcc"

2- Manually add the math lib to your libs

#link math library.. dunno why this isn't done automatically

LIBS += $(GNU_INSTALL_ROOT)/arm-none-eabi/lib/thumb/libm.a

I don't know why the linker doesn't automatically link the library but this seemed to work for me.

[maxpaynner]

This works