On Thu, Jan 8, 2026 at 7:01 PM Stephen Hemminger <[email protected]> wrote: > > On Thu, 8 Jan 2026 16:19:37 -0500 > Scott Mitchell <[email protected]> wrote: > > > On Thu, Jan 8, 2026 at 11:12 AM Stephen Hemminger > > <[email protected]> wrote: > > > > > > On Thu, 8 Jan 2026 01:13:38 -0500 > > > [email protected] wrote: > > > > > > > +#ifdef RTE_CC_GCC > > > > + /* Suppress GCC -Wmaybe-uninitialized false positive. No > > > > assembly/runtime impacts. */ > > > > + asm volatile("" : "+m" (psd_hdr)); > > > > +#endif > > > > > > > > > > Maybe rte_compiler_barrier() will do same thing? > > > > Agreed it feels like a compiler bug but looking for advice if I'm > > missing something :) > > > > My initial concern with rte_compiler_barrier is its a general barrier > > which may have broader impacts on > > optimizations and compiled code. Will that be an issue in this case? I > > wasn't sure and the approach > > in the patch is targeted at a specific variable and assembly from > > clang/gcc was the same. I will > > introduce a macro to make it cleaner and I can replace it with > > rte_compiler_barrier if preferred. > > Maybe try with -fanalyzer and it might tell you more. > I suspect some of the aliasing setting are causing issues. > Some drivers are turning on no-strict-aliasing
I have more evidence this is a GCC optimizer bug. The RTE_SUPPRESS_UNINITIALIZED_WARNING approach serves as a workaround to avoid the bug. I created a more minimal reproducer: https://gist.github.com/Scottmitch/bf23748b4588e68c9bdb8d124f92f1bd Your suspicion was correct, -fno-strict-aliasing avoids the bug but I don't think it is desirable to enable this broadly for DPDK when we have a more targeted workaround. I will reach out to RH to confirm but in the interim I suggest we keep RTE_SUPPRESS_UNINITIALIZED_WARNING (or similar alternative).
