Re: [PATCH, fortran][16 Regression] Fix PR124482 SEGV in resolve_cyclic_derived_type

Committed after Rainer confirmed the fix in bugzilla.

commit d8b00bf2e1514cd132a9febaa9849ab46cd316f5 (HEAD -> master, origin/master, 
origin/HEAD)
Author: Christopher Albert <[email protected]>
Date:   Fri Mar 13 20:50:07 2026 +0100

     fortran: Fix use-after-free in CLASS component error recovery [PR124482]

Best regards,

Jerry

On 3/14/26 11:26 AM, Jerry D wrote:
> The attached patch fixes the regression found by Rainer on Solaris Spark. It 
> manifests on x86_64 as invalid reads identified by valgrind.
> 
> I did confirm the valgrin errors before the patch and that they go away after 
> the patch. This is sufficient reason to commit this. I did not hear back from 
> Rainer yet in the PR, however if we fix it he will see in his regular builds.
> 
> Regression tested on x86_64. Valgrind tested.
> 
> OK for mainline?
> 
> I will consider backporting to 15 if reasonable. Likely this will be a combining 
> of the original fix for 106946 and this one. (easy to do).
> 
> Regards,
> 
> Jerry
> 
> From: Christopher Albert <[email protected]>
> Date: Fri, 13 Mar 2026 20:50:07 +0100
> Subject: [PATCH] fortran: Fix use-after-free in CLASS component error recovery
>   [PR124482]
> 
> The error recovery added in r16-8021 (PR106946) freed CLASS container
> symbols when removing invalid CLASS components from a derived type.
> However, gfc_build_class_symbol reuses existing containers when multiple
> components share the same class type and attributes.  Freeing the
> container for a failed component also invalidated it for previously
> committed components, causing a use-after-free detectable with valgrind
> and manifesting as a SEGV on Solaris/SPARC.
> 
> Fix by deferring CLASS container cleanup until after all failed
> components are unlinked, then freeing the container only if no remaining
> component still references it.
> 
> gcc/fortran/ChangeLog:
> 
>      PR fortran/124482
>      * decl.cc (gfc_match_data_decl): Defer CLASS container cleanup
>      until after all failed components are unlinked.  Check remaining
>      component list before freeing a shared container.
> 
> Signed-off-by: Christopher Albert <[email protected]>