Getting started with building a GCC cross-compiler
Tue Nov 25 00:15:00 GMT 2008
Dave Nadler wrote:
> While I did get a complete set of executables from
> the make, I didn't get libgcc, libstdc++, nor did I get
> the include files. What am I missing here ?
You specified --without-headers which tells the build system that there
are no libc headers available, i.e. a completely freestanding compiler.
C++ support (and libgcc and libstdc++) require a working, preexisting
libc, so that is why it didn't try to build those components.
Note that cross-compiling libstdc++ introduces its own measure of
difficulty: in order to configure the library correctly a large number
of aspects of the target's libc must be determined, and many of these
tests are in the form of link tests to see what the library supports.
This means you need to be able to link executables when running the
libstdc++ configure script, which for a bare metal target generally
means you need all of the board support files (CRT/linker script/syscall
stubs) existing in a place visible to the newly built compiler.
In the specific case of newlib, the build system has a predefined list
of what the library supports and so in theory it should be possible to
cross-build libstdc++ without being able to link, but only if you're
using newlib and only if inform the build system of this fact
(--with-newlib.) However the configure scripts are constantly evolving
and I think the general consensus is moving toward requiring that for
bare metal targets the BSP files be available for building a cross
libstdc++ (i.e. requiring link tests again), since otherwise relying on
assumed defaults is too risky. But 3.4 is so ancient that none of this
may apply. In any case if all else fails you can do it two phases, i.e.
get plain C working and to the point where it can link executables and
then using that sysroot re-build the compiler with C++ enabled.
> (and then I'll
> see what work I must do to adapt to the bare-metal
If you are using newlib then you will want to adapt the syscall stubs in
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