Re: openbios fails to build with gcc-16 (powerpc code)

On 8/6/26 12:56, Michael Tokarev wrote:
> Hi!
> 
> Since debian switch from gcc-15 to gcc-16, qemu fails to build openbios-powerpc:
> 
> powerpc-linux-gnu-gcc -m32 -mcpu=604 ...\
>   roms/openbios/arch/ppc/qemu/start.S
> 
> roms/openbios/arch/ppc/qemu/start.S:292: Error: unrecognized opcode: `clrldi'
> roms/openbios/arch/ppc/qemu/start.S:293: Error: unrecognized opcode: `mtmsrd'
> roms/openbios/arch/ppc/qemu/start.S:178: Error: unrecognized opcode: `std'
> [a lot of other similar errors]
> 
> I know nothing about powerpc assembler.  Google tells me mtmsrd is a 64bit-only
> instruction which can't be used in 32bit mode (which is in effect here).
> 
> It feels like start.S uses the wrong assembly?  I wonder how it worked before..

The issue boils down to missing -many option to as when using gcc-16.
With gcc-15, as is being run with
   -a32 -mppc -many -mbig
but gcc-16 omits -many:
   -a32 -mppc -mbig
Explicitly adding -Wa,-many lets the build to proceed.

It still fails down the line with:

roms/openbios/libopenbios/client.c: In function ‘handle_calls’:
roms/openbios/libopenbios/client.c:249:16: warning: variable ‘j’ set but not used [-Wunused-but-set-variable=]
   249 |         int i, j, dstacksave;
       |                ^
roms/openbios/libopenbios/client.c: In function ‘of_client_interface’:

which also becomes a fatal error due to -Werror.

Adding -Wno-error=unused-but-set-variable lets the build to succeed.

Thanks,

/mjt

> Additionally, there's this new error (due to -Werror being in effect),
> but it is easy to deal with:
> 
> In file included from /build/pkg/build/roms/openbios/kernel/bootstrap.c:28:
> roms/openbios/kernel/bootstrap.c: In function ‘write_dictionary’:
> roms/openbios/kernel/include/dict.h:12:16: warning: initializer-string for array of ‘char’ truncates NUL terminator but destination lacks ‘nonstring’ 
> attribute (9 chars into 8 available) [-Wunterminated-string-initialization]
>     12 | #define DICTID "OpenBIOS"
>        |                ^~~~~~~~~~
> roms/openbios/kernel/bootstrap.c:170:35: note: in expansion of macro ‘DICTID’
>    170 |                 .signature      = DICTID,
>        |                                   ^~~~~~
> 
> 
> FWIW,
> 
> /mjt
>