Re: [PATCH v3 1/6] test/soring: fix buffer overflow warnings with LTO

Stephen Hemminger
2026-01-19T22:48:30Z

On Fri, 16 Jan 2026 10:32:52 +0100
Morten Brørup <mb@smartsharesystems.com> wrote:

> > From: Stephen Hemminger [mailto:stephen@networkplumber.org]
> > Sent: Friday, 16 January 2026 07.46
> >
> > When building with LTO (Link Time Optimization), GCC performs
> > aggressive cross-compilation-unit inlining. This causes the compiler
> > to analyze all code paths in __rte_ring_do_dequeue_elems(), including
> > the 16-byte element path (__rte_ring_dequeue_elems_128), even when
> > the runtime element size is only 4 bytes.
> >
> > The static analyzer sees that the 16-byte path would copy
> > 32 elements * 16 bytes = 512 bytes into a 128-byte buffer
> > (uint32_t[32]),
> > triggering -Wstringop-overflow warnings.
> >
> > The existing #pragma GCC diagnostic suppression in rte_ring_elem_pvt.h
> > doesn't help because with LTO the warning context shifts to the test
> > file where the inlined code is instantiated.
> >
> > Fix by sizing all buffers passed to soring acquire/dequeue functions
> > for the worst-case element size (16 bytes = 4 * sizeof(uint32_t)).
> > This satisfies the static analyzer without changing runtime behavior.
>
> Using wildly oversized buffers doesn't seem like a recommendable solution.
> If the ring library is ever updated to support cache size elements (64 byte), the buffers would have to be oversize by factor 16.

The analysis (from AI) is that compiler is getting confused. Since there is no good
way other than turning of LTO for the test to tell the compiler

>
> Maybe adding __rte_assume(sor->esize == sizeof(uint32_t)); immediately before calling each of the affected soring functions would fix the problem instead?
>
> It's only a test application, so oversized buffers as a workaround is acceptable.
>
> But if it serves as guidance for real applications, a better solution/workaround would be preferable.