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Forum: ARM programming with GCC/GNU tools Float Issue in GCC4.4.2 with CortexM3 ARM processor


Author: Prabu 84 (Company: Nimble) (prabu)
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Hi all,
I am using yagarto ARMTools chain,

 Binutils-2.20
 Newlib-1.18.0
 GCC-4.4.2
 GDB-7.0.1

In my make file options(for CortexM3 processor,LPC17series),
-mcpu=cortex-m3 -mthumb mfpu=fpa (or) -mfpu=vfp

with this options My program going to hangs when i use simple float 
operations(covert float to int using type cast,substract float with 
integer etc.This is for supporting ftoa() api).

Same code working form me in following makefile options(ARM7 
processor,LPC23xx,21xxseries) in my another project,
-mcpu=arm7tdmi -mthumb-interwork.I havn't seen any issue past 6months.

Please guide me??

If any one already faced this issue please share your knowledge???

FYI:I am using LPC17 seires with FreeRTOS.

Author: gprandst (Guest)
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Hi,
I want to confirm this problem, but I am using an ARM7 LPC2478 and do 
not use the thumb set.
At google I found a similar report concerning x86:
http://old.nabble.com/newlib-error-when-printf-flo...

Seems to be a general problem which is new in 1.18.

Regards,
Gottfried

Author: Clifford Slocombe (clifford)
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Prabu 84 wrote:

>
> In my make file options(for CortexM3 processor,LPC17series),
> -mcpu=cortex-m3 -mthumb mfpu=fpa (or) -mfpu=vfp
>

So why would you use -mfpu=fpa of vfp when a Cortex-M3 has neither an 
FPA not a VFP?  These settings will cause the generation of instructions 
for a math co-processor that does not exist.

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