ARM Cortex-M3 (Stellaris LM3S811) soft float problem (GCC/QEMU)

The Cortex-M3 supports only the Thumb-2 instruction set, calling an ARM function will cause an Usage Fault. I'm guessing there's a compiler/linker flag missing in your setup, or some bug in newlib's build process.

-a

the

compiler/linker

I'm having a similar problem on LM3S9B92-EK. I'm using GNU Arm toolkit configured with the '--with-float=soft' option. The project is compiled with -mthumb (Thumb-2), -msoft-float (Software floating point emulation),

-mcpu=cortex-m3 (Cortex-M3 architecture) and a few other flags. I'm linking it against libdriver and libgcc (the one that's installed into the thumb subdirectory).

Mine crashes (HardFault) on a simple comparison of 2 floats: float a = 1.2f; float b = 1.1f;

UARTprintf ("\nLess %d..\n", (a < b));

And I'm pretty sure that the UART printout is working correctly..

Well, I doubt it's newlib - I could be wrong, but I guess that libgcc should contain software floating point emulation code.

I'm a bit doubtful in the linker script that I wrote, because none of the supplied scripts linked without errors. Another suspicion would be the startup_gcc.c file, which I haven't modified much (due to the lack of working float sample code). Or, it could actually be a bug in the libgcc..

. Tried to keep a long post short =P.

All suggestions are welcome, Thank You

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linking

libgcc..

Well, as it turned out, libgcc had been configured wrong (for ARM7TDMI). I had to configure gcc with this:

--target=${GCC_TARGET} --prefix=${ARMTOOLS} --enable-interwork

--enable-multilib --enable-languages="c,c++" --with-newlib

--with-headers=../../src/newlib-${NEWLIB_VERSION}/newlib/libc/include

--with-float=soft --with-cpu=cortex-m3 --with-tune=cortex-m3

--with-mode=thumb --disable-libssp

where

NEWLIB_VERSION=1.18.0 GCC_TARGET=arm-none-eabi

and

ARMTOOLS=/usr/local/arm

Hope this helps..

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