Re: [Linaro-TCWG-CI] gcc-16-3649-gc440b585ba3: 4 regressions on master-thumb_m3_softfp_eabi

I'd like to apologize for causing these regressions. Below
I've copied out the relevant parts from the logs. To me it
looks like _Xv is a reserved identifier.

I'll prepare a patch to fix the issue.

On 9/9/25 6:54 AM, [email protected] wrote:
> Dear contributor,
> 
> Our automatic CI has detected problems related to your patch(es). Please find some details below.
> 
> In  arm-eabi cortex-m3 softfp, after:
>    | commit gcc-16-3649-gc440b585ba3
>    | Author: Luc Grosheintz <[email protected]>
>    | Date:   Thu Sep 4 14:20:28 2025 +0200
>    |
>    |     libstdc++: Implement constant_wrapper, cw from P2781R9.
>    |
>    |     This is a partial implementation of P2781R9. It adds std::cw and
>    |     std::constant_wrapper, but doesn't modify __integral_constant_like for
>    |     span/mdspan.
>    | ... 25 lines of the commit log omitted.
> 
> Produces 4 regressions:
>    |
>    | regressions.sum:
>    | Running g++:g++.old-deja/old-deja.exp ...
>    | FAIL: g++.old-deja/g++.robertl/eb39.C -std=c++26 (test for excess errors)

Code:
4651:  template<_CwFixedValue _Xv, typename>
4652:  struct constant_wrapper : _CwOperators
4653:  {


Compiler error:
/home/tcwg-buildslave/workspace/tcwg_gnu_0/abe/builds/x86_64-pc-linux-gnu/arm-eabi/gcc-gcc.git~master-stage2/arm-eabi/libstdc++-v3/include/type_traits:4651:26: 
error: expected '>' before numeric constant

My guess is that _Xv is a reserved name. It's not on the list
of common bad identifiers [1], but it's the only guess I have.

[1]: https://gcc.gnu.org/onlinedocs/libstdc++/manual/source_code_style.html

>    | FAIL: g++.old-deja/g++.robertl/eb54.C -std=c++26 (test for excess errors)

Same as above.

>    | UNRESOLVED: g++.old-deja/g++.robertl/eb54.C -std=c++26 compilation failed to produce executable

Same as above.

>    | FAIL: g++.old-deja/g++.warn/iomanip.C -std=gnu++26 (test for excess errors)

Same as above.

> Used configuration :
>   *CI config* tcwg_gnu_embed_check_gcc arm-eabi -mthumb -march=armv7-m -mtune=cortex-m3 -mfloat-abi=softfp -mfpu=auto
>   *configure and test flags:* --target arm-eabi --disable-multilib --with-mode=thumb --with-cpu=cortex-m3 --with-float=softfp --target_board=-mthumb/-march=armv7-m/-mtune=cortex-m3/-mfloat-abi=softfp/-mfpu=auto qemu_cpu=cortex-m3
> 
> We track this bug report under https://linaro.atlassian.net/browse/GNU-1676. Please let us know if you have a fix.
> 
> If you have any questions regarding this report, please ask on [email protected] mailing list.
> 
> -----------------8<--------------------------8<--------------------------8<--------------------------
> 
> The information below contains the details of the failures, and the ways to reproduce a debug environment:
> 
> You can find the failure logs in *.log.1.xz files in
>   * https://ci.linaro.org/job/tcwg_gnu_embed_check_gcc--master-thumb_m3_softfp_eabi-build/518/artifact/artifacts/00-sumfiles/
> The full lists of regressions and improvements as well as configure and make commands are in
>   * https://ci.linaro.org/job/tcwg_gnu_embed_check_gcc--master-thumb_m3_softfp_eabi-build/518/artifact/artifacts/notify/
> The list of [ignored] baseline and flaky failures are in
>   * https://ci.linaro.org/job/tcwg_gnu_embed_check_gcc--master-thumb_m3_softfp_eabi-build/518/artifact/artifacts/sumfiles/xfails.xfail
> 
> Current build   : https://ci.linaro.org/job/tcwg_gnu_embed_check_gcc--master-thumb_m3_softfp_eabi-build/518/artifact/artifacts
> Reference build : https://ci.linaro.org/job/tcwg_gnu_embed_check_gcc--master-thumb_m3_softfp_eabi-build/517/artifact/artifacts
> 
> Instruction to reproduce the build : https://gitlab.com/LinaroLtd/tcwg/ci/interesting-commits/-/raw/master/gcc/sha1/c440b585ba374b6348ef223e4891a717a1f6660c/tcwg_gnu_embed_check_gcc/master-thumb_m3_softfp_eabi/reproduction_instructions.txt
> 
> Full commit : See in git+ssh://[email protected]/git/gcc.git