Re: GCC: Canadian Cross + Dynamic linker issues

[Ekaitz Zarraga]

Let me please bump this thread a little bit, since I didn't get
any answer

> Hi,
>
> I've been struggling with GCC package definition for a while and I hope 
> someone
> can help me solve or improve what I think are issues in its definition.
>
> I'm working on a R7RS-Small Scheme implementation that compiles to RISC-V
> assembly and I'm finding many issues to create a RISC-V cross compiler.
>
> Consider the following manifest file for my project, where I need a GCC for
> a 32 bit RISC-V machine:
>
>     (use-modules (gnu packages cross-base)
>                  (gnu packages gcc)
>                  (gnu packages embedded))
>
>     (packages->manifest
>
>       (let* ((triplet "riscv32-unknown-elf")
>              (binutils (cross-binutils triplet)))
>             (list
>               binutils
>               (cross-gcc triplet
>                          #:xbinutils binutils
>                          #:libc #f))))
>
>
> The call to cross-gcc fails to find a dynamic linker and the installation
> fails.
>
> This happens because GCC package definition calls to the function
> `glibc-dynamic-linker` in `gnu/packages/bootstrap.scm`, that contains a list 
> of
> possible triplets with their associated dynamic linker file name.
>
> I don't really understand why does a generic GCC package need to call a
> function from the bootstrap module by default. I can see why GCC takes a huge
> part on the bootstrapping process of Guix but I think that kind of coupling is
> compromising the flexibility of the generic GCC package. Please, correct me if
> I'm wrong.
>
> That said, in the past, I sent a patch[^patch] as a workaround because I saw
> some references to AVR on the `glibc-dynamic-linker` that also used a fake
> dynamic linker to avoid the function to fail but I got no response so I'm not
> sure if the change makes any sense.
>
> Digging further on the GCC package definition I found a note that says:
>
> > ;; None of the flags below are needed when doing a Canadian cross.
> > ;; TODO: Simplify this.
>
> So I wonder if that's the source of the problems I'm finding here.
>
> The `glibc-dynamic-linker` function is being used twice in the block preceded
> by that comment and only once more below, in some patches we are applying on
> top of the source code.
>
> At this level I'm not sure if there's any way to "fix" GCC package definition
> to be able to create cross-compilers or if I should create a separate package
> for my specific use-case and forget about all this.
>
> I would love to take part and try to simplify the GCC package description, but
> as it is a fundamental package looks like a huge responsibility so I'd like to
> have some guidance first.
>
> Thanks,
>
> Ekaitz
>
> [^patch]: https://issues.guix.gnu.org/46059