Re: Building newlib without -mhard-float

[Rick Mann <rmann at latencyzero dot com>]

On Sep 6, 2007, at 5:06 PM, Rick Mann wrote:

> Here's another odd thing I'm seeing. With my current build of the  
> tools & multilib (using --target=arm-elf and --with-cpu=xscale), if  
> I write single- and double-precision floating point code like this:
>
> 	volatile double a = 1.5;
> 	volatile double b = 4.0;
> 	int c = (int) (a * b);
>
> The compiler generates calls to __muldf3() and the like and  
> everything links and executes fine.
>
> [...]

> But, if I call sprintf(), the linker complains about routines like  
> __muldf3 (and many others) not being found:
>
>
> /usr/local/arm3/lib/gcc/arm-elf/4.2.1/../../../../arm-elf/lib/libc.a 
> (lib_a-dtoa.o): In function `_dtoa_r':
> /Users/rmann/Desktop/gcc2/newlib-1.15.0/build/arm-elf/newlib/libc/ 
> stdlib/../../../../../newlib/libc/stdlib/dtoa.c:463: undefined  
> reference to `__muldf3'
>
> Even more interesting, if I leave in my own floating-point code,  
> that reference in _dtoa_r to __muldf3 is linked fine. If I remove  
> my own floating-point code, the error comes back. It seems that GCC  
> is unable to link the floating-point math calls in libc.a on its  
> own, but me making reference to them in my main() makes it okay.

Well, I feel kinda dumb. I moved the -lgcc to the end of my list, and  
it links okay now (I still need to fill in the low-level stubs, but  
the floating-point is doing much better now. I wonder how long that  
simple change has been an issue.

I'm also not sure why putting -lgcc last makes a difference, but I  
guess I remember reading something about bidirectional references  
requiring the libraries to be listed multiple times.

Back in my glorious past, using CodeWarrior, you could control the  
link order by rearranging the files in the "Link" pane of the project  
window. Such reordering did NOT affect whether or not symbols were  
found, and CW was significantly faster than GCC.

OTOH, I wouldn't be able to do PXA320 development on my Mac with  
CodeWarrior, so I'm glad I have GCC.

--
Rick