Re: [avr-gcc-list] Link Eorror in Combining C and assembly source files

[Dean Ferreyra]

Shilin Yu wrote:
> I have tried by it doesn't work either.

Yes, I was wrong about the underscore, sorry.

> I seems like that WinAVR uses the GNU Assembler(GAS), not the AVR Assembler

Sorry, I don't know what you mean.

Can you share the actual command lines you're using to compile and
assemble the files?  My new guess is that when you are assembling the
file, avr-gcc is also trying to link.

One quick test I tried was to make two files, a.c:

    volatile unsigned char sched_mode;

    int main(void)
    {
        return 0;
    }

and b.S:

    .extern sched_mode
            LDS R18, sched_mode

and then I compiled them separately and then linked them like so:

    $ avr-gcc -mmcu=atmega128 -c a.c

    $ avr-gcc -mmcu=atmega128 -c b.S

    $ avr-gcc -mmcu=atmega128 -o a.out a.o b.o

    $ ls -l a.out
    -rwxr-xr-x 1 dean None 2674 Sep  5 00:59 a.out*

Can you try something along those lines?

On the other hand, without the -c, the second command will generate an
error, something like:

    $ avr-gcc -mmcu=atmega128 b.S
    .../crtm128.o:(.init9+0x0): undefined reference to `main'
    .../ccJeooXf.o:(.text+0x2): undefined reference to `sched_mode'

Dean

> 
> 2008/9/5 Dean Ferreyra <address@hidden <mailto:address@hidden>>
> 
>     Try using _sched_mode in your assembly code instead.  If I remember
>     correctly, the C compiler automatically prefixes symbols with an
>     underscore.
> 
>     Dean
> 
>     Shilin Yu wrote:
>     >    I met an link error when build a project with .c and .S files
>     >
>     >    the c file  like this:
>     >          ...
>     >          volatile unsigned char     sched_mode;
>     >          ...
>     >
>     >
>     >    the assembly  file like this:
>     >          .extern    sched_mode
>     >          ...
>     >          LDS R18, sched_mode
>     >          ...
>     >
>     >
>     >    when I build the project. the link error about the assembly
>     file output:
>     >
>     >     (.text+0x32): undefined reference to `sched_mode'
>     >
>     >
>     >     Any reply is welcome! Thanks!
>     >
>     > --
>     > Sincerely yours,
>     > Shilin Yu
>     >
> 
> 
> 
> 
> -- 
> Sincerely yours,
> Shilin Yu