[arm-gnu] Cortex-M3 and Floating Point Problems

[Mark Mulrooney]

The printf being pulled in is from the thumb2/libc.a file according to the map file; I've attached the map file. 

We are not using any macros iprintf as far as I know. 

I'm not sure I understand what you mean by the CodeBench printf vs the alternative printf. We do not use CodeBench at all, we are using makefiles and the compiler. 

Thanks,
Mark

-----Original Message-----
From: Carlos O'Donell [mailto:carlos_odonell at mentor.com] 
Sent: Thursday, June 21, 2012 15:18
To: Mark Mulrooney
Cc: arm-gnu at codesourcery.com
Subject: Re: [arm-gnu] Cortex-M3 and Floating Point Problems

On 6/21/2012 2:48 PM, Mark Mulrooney wrote:
> It appears you are correct, good catch! Now my next question would be 
> why. I'm using the standard libraries provided by CodeSourcery. I did 
> notice while stepping through the code that the last assembly 
> instruction before branching to printf is a ldrd call and I also 
> noticed there is a compiler option for -mfix-cortex-m3-ldrd. I added 
> that in but it still doesn't seem to work correctly.

The `-mfix-cortex-m3-ldrd' is automatically enabled when you specify -mcpu=cortex-m3.

You haven't provided a test case or linker map file so all we can do is guess.

The Sourcery CodeBench bare-metal C library is ISO C compabitle and therefore provides %f support.

Care to add `-Wl,-Map,linkermap.txt` to your final link with gcc and look to see there where printf is coming from?

Some other options might be:

* You used macro tricks to call iprintf instead of printf
  to make the executable smaller, but forgot iprintf doesn't
  support %f?

* You aren't using the CodeBench printf, and the alternate
  printf doesn't support %f?

* And lastly... the CodeBench printf has a bug.

Cheers,
Carlos.
--
Carlos O'Donell
Mentor Graphics / CodeSourcery
carlos_odonell at mentor.com
carlos at codesourcery.com
+1 (613) 963 1026


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