Re: trouble building with included libraries

[Kai Ruottu <kai dot ruottu at wippies dot com>]

15.3.2014 7:49, Sam Hansen kirjoitti:
> I am attempting to compile gcc, configured as a cross compiler.  I
> explicitly do not have libgmp, libmpfr, or libmpc installed on my
> system.  The documentation at http://gcc.gnu.org/wiki/InstallingGCC
> indicates that I may compile these libraries as part of the gcc
> compilation process overall.

Yes, they will be automatically built and the GCC executables (xgcc, 
cc1,...) will
be linked against these libraries. They will be done for the HOST 
system, not
for the TARGET (here 'avr') system.

> ...
> configure: error: cannot compute suffix of object files: cannot compile
> See `config.log' for more details.
> make[1]: *** [configure-target-libgcc] Error 1
> make[1]: Leaving directory `/home/sam/objdir'
> make: *** [all] Error 2

Meanwhile 'libgcc' is a library made for the TARGET system. And made 
with the
just built GCC executables. So you couldn't get this far if there was 
any problem
with the gmp, mpfr and mpc libraries!

> The error is logged in objdir/avr/libgcc/config.log.

So you should look at this file!

>    I understand
> this indicates that the prerequisite libraries weren't set up
> correctly prior to the compilation?

Yes, the not-told prerequisite is the "target C library" being 
installed!  In a native
build this prerequisite is obviously set up otherwise one couldn't 
compile anything,
the target headers are required in compiling, and couldn't link 
anything, the target
library binaries are required...  Generally when something will be 
compiled one must
have headers to use and when linking one must have library binaries to 
use!  When
configuring 'libgcc' it is possible that some link tests are used in 
order to see what
functions the base target C library has or how these functions do 
behave...  So for a
cross compiler the target C library being preinstalled is just as 
natural prerequisite
as it is for a native compiler!  The exception is when one uses 
'newlib', then only the
target headers are needed during the build. And not even them if 
'--without-headers'
is used...

I think that for AVR there is some "custom" C library, used in the 
'avrgcc' release. Or
one can use the free 'newlib' as that target C library, building it at 
the same time with
'gcc', 'gmp', 'mpfr' and 'mpc' for the HOST and 'libgcc', 'libstdc++' 
etc for the TARGET.
In the latter case using '--with-newlib' in the GCC configure.

The 'fixincludes' phase in the GCC build also requires the target C 
headers to be available
for 'fixing' them.  Every GCC builder surely sees this phase happening 
and should then
think what on earth it does. Some docs for it can be seen in the net like :

http://ewontfix.com/12/