On Thu, Jul 31, 2025 at 5:47 PM Yangyu Chen <[email protected]> wrote: > > When building with LTO, DECL_VINDEX is not always set for virtual > functions, which allows virtual functions to be incorrectly treated as > non-virtual and then being multi-versioned, and causes errors sometimes. > > This patch addresses the issue by ensuring that we also check > DECL_VIRTUAL_P in addition to DECL_VINDEX when handling virtual > functions during multiversioning.
I think checking DECL_VINDEX is flawed - it's only relevant for creating OBJ_TYPE_REFs IIRC. That is, it's irrelevant to GIMPLE and thus freed in free-lang-data (which we unfortunately run only with -flto). So, can you test removing the DECL_VINDEX check and only rely on DECL_VIRTUAL_P? Thanks, Richard. > gcc/ChangeLog: > > * config/aarch64/aarch64.cc > (aarch64_generate_version_dispatcher_body): Check DECL_VIRTUAL_P for virtual > functions for LTO handling. > * config/i386/i386-features.cc > (ix86_generate_version_dispatcher_body): Ditto. > * config/riscv/riscv.cc (riscv_generate_version_dispatcher_body): > Ditto. > * config/rs6000/rs6000.cc (rs6000_generate_version_dispatcher_body): > Ditto. > > Signed-off-by: Yangyu Chen <[email protected]> > --- > This should also be backported to GCC stable branches. > --- > gcc/config/aarch64/aarch64.cc | 2 +- > gcc/config/i386/i386-features.cc | 2 +- > gcc/config/riscv/riscv.cc | 2 +- > gcc/config/rs6000/rs6000.cc | 2 +- > 4 files changed, 4 insertions(+), 4 deletions(-) > > diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc > index fff8d9da49d..fd77e24ce12 100644 > --- a/gcc/config/aarch64/aarch64.cc > +++ b/gcc/config/aarch64/aarch64.cc > @@ -20763,7 +20763,7 @@ aarch64_generate_version_dispatcher_body (void > *node_p) > not. This happens for methods in derived classes that override > virtual methods in base classes but are not explicitly marked as > virtual. */ > - if (DECL_VINDEX (versn->decl)) > + if (DECL_VIRTUAL_P (versn->decl) || DECL_VINDEX (versn->decl)) > sorry ("virtual function multiversioning not supported"); > > fn_ver_vec.safe_push (versn->decl); > diff --git a/gcc/config/i386/i386-features.cc > b/gcc/config/i386/i386-features.cc > index 31f3ee2ef17..043e86ece8e 100644 > --- a/gcc/config/i386/i386-features.cc > +++ b/gcc/config/i386/i386-features.cc > @@ -4421,7 +4421,7 @@ ix86_generate_version_dispatcher_body (void *node_p) > not. This happens for methods in derived classes that override > virtual methods in base classes but are not explicitly marked as > virtual. */ > - if (DECL_VINDEX (versn->decl)) > + if (DECL_VIRTUAL_P (versn->decl) || DECL_VINDEX (versn->decl)) > sorry ("virtual function multiversioning not supported"); > > fn_ver_vec.safe_push (versn->decl); > diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc > index a0657323f65..90f2cbce68e 100644 > --- a/gcc/config/riscv/riscv.cc > +++ b/gcc/config/riscv/riscv.cc > @@ -13747,7 +13747,7 @@ riscv_generate_version_dispatcher_body (void *node_p) > not. This happens for methods in derived classes that override > virtual methods in base classes but are not explicitly marked as > virtual. */ > - if (DECL_VINDEX (versn->decl)) > + if (DECL_VIRTUAL_P (versn->decl) || DECL_VINDEX (versn->decl)) > sorry ("virtual function multiversioning not supported"); > > fn_ver_vec.safe_push (versn->decl); > diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc > index 12dbde2bc63..0c13d524124 100644 > --- a/gcc/config/rs6000/rs6000.cc > +++ b/gcc/config/rs6000/rs6000.cc > @@ -25656,7 +25656,7 @@ rs6000_generate_version_dispatcher_body (void *node_p) > not. This happens for methods in derived classes that override > virtual methods in base classes but are not explicitly marked as > virtual. */ > - if (DECL_VINDEX (version->decl)) > + if (DECL_VIRTUAL_P (version->decl) || DECL_VINDEX (version->decl)) > sorry ("Virtual function multiversioning not supported"); > > fn_ver_vec.safe_push (version->decl); > -- > 2.49.0 >
