[Linaro-TCWG-CI] gcc-15-7765-g3866ca796d5: 8 regressions on master-thumb_m7_hard_eabi

[Christophe Lyon]

Hi Jonathan,

On Sun, 2 Mar 2025 at 23:28, Jonathan Wakely via Gcc-regression
<gcc-regression@gcc.gnu.org> wrote:
>
> On Sun, 2 Mar 2025 at 02:42, <ci_notify@linaro.org> wrote:
> >
> > Dear contributor,
> >
> > Our automatic CI has detected problems related to your patch(es). Please find some details below.
> >
> > In  arm-eabi cortex-m7 hard, after:
> >   | commit gcc-15-7765-g3866ca796d5
> >   | Author: Jonathan Wakely <jwakely@redhat.com>
> >   | Date:   Thu Feb 27 13:27:17 2025 +0000
> >   |
> >   |     libstdc++: Fix ranges::move and ranges::move_backward to use iter_move [PR105609]
> >   |
> >   |     The ranges::move and ranges::move_backward algorithms are supposed to
> >   |     use ranges::iter_move(iter) instead of std::move(*iter), which matters
> >   |     for an iterator type with an iter_move overload findable by ADL.
> >   | ... 16 lines of the commit log omitted.
> >
> > Produces 8 regressions:
> >   |
> >   | regressions.sum:
> >   | Running libstdc++:libstdc++-dg/conformance.exp ...
> >   | FAIL: 25_algorithms/move/constrained.cc -std=gnu++20 (test for excess errors)
> >   | UNRESOLVED: 25_algorithms/move/constrained.cc -std=gnu++20 compilation failed to produce executable
> >   | FAIL: 25_algorithms/move/constrained.cc -std=gnu++26 (test for excess errors)
> >   | UNRESOLVED: 25_algorithms/move/constrained.cc -std=gnu++26 compilation failed to produce executable
> >   | ... and 4 more
>
> It looks like thumb has some unusual linking requirements that I'm not
> familiar with, so undefined functions (which are never actually called
> in the test) cause linker errors:
>
> /home/tcwg-buildslave/workspace/tcwg_gnu_1/abe/builds/x86_64-pc-linux-gnu/arm-eabi/gcc-gcc.git~master-stage2/arm-eabi/libstdc++-v3/include/bits/iterator_concepts.h:155:(.text._Z6test06N8pr1056091IE+0x6):
> undefined reference to `pr105609::iter_move(pr105609::I const&)'
> /home/tcwg-buildslave/workspace/tcwg_gnu_1/abe/builds/destdir/x86_64-pc-linux-gnu/arm-eabi/bin/ld:
> (_ZN8pr1056099iter_moveERKNS_1IE): Unknown destination type
> (ARM/Thumb) in /tmp/ccqKQGzN.o

This is a "recent" linker warning, which I added sometime during last
year (so you need recent binutils if you want to try to reproduce the
problem).
It means that for some reason the destination symbol lacks a tag (asm
directive) saying whether it's a thumb or an arm function. This is
used by the linker when deciding which type of stub to insert (if
any).
For instance: ".type myfunc, %function"
but normally the compiler adds this for you.

But you mention "undefined functions", so that would probably be the
reason, but how can the link succeed? Are you linking with "-z undefs"
?

Thanks,

Christophe

> /home/tcwg-buildslave/workspace/tcwg_gnu_1/abe/builds/x86_64-pc-linux-gnu/arm-eabi/gcc-gcc.git~master-stage2/arm-eabi/libstdc++-v3/include/bits/iterator_concepts.h:155:(.text._Z6test06N8pr1056091IE+0x6):
> dangerous relocation: unsupported relocation
> /home/tcwg-buildslave/workspace/tcwg_gnu_1/abe/builds/x86_64-pc-linux-gnu/arm-eabi/gcc-gcc.git~master-stage2/arm-eabi/libstdc++-v3/include/bits/ranges_algobase.h:326:(.text._Z6test06N8pr1056091IE+0xc):
> undefined reference to `pr105609::I::operator++()'
> /home/tcwg-buildslave/workspace/tcwg_gnu_1/abe/builds/destdir/x86_64-pc-linux-gnu/arm-eabi/bin/ld:
> (_ZN8pr1056091IppEv): Unknown destination type (ARM/Thumb) in
> /tmp/ccqKQGzN.o
> /home/tcwg-buildslave/workspace/tcwg_gnu_1/abe/builds/x86_64-pc-linux-gnu/arm-eabi/gcc-gcc.git~master-stage2/arm-eabi/libstdc++-v3/include/bits/ranges_algobase.h:326:(.text._Z6test06N8pr1056091IE+0xc):
> dangerous relocation: unsupported relocation
> /home/tcwg-buildslave/workspace/tcwg_gnu_1/abe/builds/destdir/x86_64-pc-linux-gnu/arm-eabi/bin/ld:
> /home/tcwg-buildslave/workspace/tcwg_gnu_1/abe/builds/x86_64-pc-linux-gnu/arm-eabi/gcc-gcc.git~master-stage2/arm-eabi/libstdc++-v3/include/bits/ranges_algobase.h:323:(.text._Z6test06N8pr1056091IE+0x16):
> undefined reference to `pr105609::I::operator==(pr105609::I) const'
> /home/tcwg-buildslave/workspace/tcwg_gnu_1/abe/builds/destdir/x86_64-pc-linux-gnu/arm-eabi/bin/ld:
> (_ZNK8pr1056091IeqES0_): Unknown destination type (ARM/Thumb) in
> /tmp/ccqKQGzN.o
> /home/tcwg-buildslave/workspace/tcwg_gnu_1/abe/builds/x86_64-pc-linux-gnu/arm-eabi/gcc-gcc.git~master-stage2/arm-eabi/libstdc++-v3/include/bits/ranges_algobase.h:323:(.text._Z6test06N8pr1056091IE+0x16):
> dangerous relocation: unsupported relocation
>
> I think I should be able to workaround this.
>