* [PATCH] c++: ICE initing lifetime-extended constexpr var [PR107079] @ 2023-02-08 21:01 Marek Polacek 2023-02-09 0:00 ` Jason Merrill 0 siblings, 1 reply; 4+ messages in thread From: Marek Polacek @ 2023-02-08 21:01 UTC (permalink / raw) To: Jason Merrill, GCC Patches, Patrick Palka (This may not be a complete fix but I got stuck so I'm posting what I have, which at least fixes the ICE.) We ICE on the simple: struct X { const X* x = this; }; constexpr const X& x = X{}; where store_init_value initializes 'x' with &TARGET_EXPR <D.2768, {.x=(const struct X *) &<PLACEHOLDER_EXPR struct X>}> but we must lifetime-extend via extend_ref_init_temps and we get _ZGR1x_.x = (const struct X *) &<PLACEHOLDER_EXPR struct X> >>>;, (const struct X &) &_ZGR1x_; Since 'x' was declared constexpr, we do cxx_constant_init and we hit the preeval code added in r269003 while evaluating the INIT_EXPR: _ZGR1x_.x = (const struct X *) &<PLACEHOLDER_EXPR struct X> >>> but we have no ctx.ctor or ctx.object here so lookup_placeholder won't find anything that could replace X and we ICE on 7861 /* A placeholder without a referent. We can get here when 7862 checking whether NSDMIs are noexcept, or in massage_init_elt; 7863 just say it's non-constant for now. */ 7864 gcc_assert (ctx->quiet); because cxx_constant_init means !ctx->quiet. It's not correct that there isn't a referent. I think the following patch is a pretty straightforward fix: pass the _ZGR var down to maybe_constant_init so that it can replace the PLACEHOLDER_EXPR with _ZGR1x_. What I wasn't able to make work is the commented assert in the test. It doesn't pass because we complain that _ZGR1x_ isn't a constexpr variable, but making it so would just result in "used in its own initializer" (which is true). I notice that while clang++ compiles the assert fine, MSVC++/icc reject it as non-constant. So maybe we don't have to/shouldn't make it work. Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? PR c++/107079 gcc/cp/ChangeLog: * call.cc (set_up_extended_ref_temp): Pass var to maybe_constant_init. gcc/testsuite/ChangeLog: * g++.dg/cpp0x/constexpr-nsdmi2.C: New test. --- gcc/cp/call.cc | 2 +- gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C | 9 +++++++++ 2 files changed, 10 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc index f7c5d9da94b..a0afab9b26a 100644 --- a/gcc/cp/call.cc +++ b/gcc/cp/call.cc @@ -13583,7 +13583,7 @@ set_up_extended_ref_temp (tree decl, tree expr, vec<tree, va_gc> **cleanups, /* If the initializer is constant, put it in DECL_INITIAL so we get static initialization and use in constant expressions. */ - init = maybe_constant_init (expr); + init = maybe_constant_init (expr, var); /* As in store_init_value. */ init = cp_fully_fold (init); if (TREE_CONSTANT (init)) diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C new file mode 100644 index 00000000000..6dbb7eb739a --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C @@ -0,0 +1,9 @@ +// PR c++/107079 +// { dg-do compile { target c++11 } } + +struct X { + const X* x = this; +}; +constexpr const X& x = X{}; +// TODO: Should the assert pass? +//static_assert(x.x == &x); base-commit: 77bb54b1b07add45007c664724b726541d672ef3 -- 2.39.1 ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] c++: ICE initing lifetime-extended constexpr var [PR107079] 2023-02-08 21:01 [PATCH] c++: ICE initing lifetime-extended constexpr var [PR107079] Marek Polacek @ 2023-02-09 0:00 ` Jason Merrill 2023-02-09 2:15 ` [PATCH v2] " Marek Polacek 0 siblings, 1 reply; 4+ messages in thread From: Jason Merrill @ 2023-02-09 0:00 UTC (permalink / raw) To: Marek Polacek, GCC Patches, Patrick Palka On 2/8/23 13:01, Marek Polacek wrote: > (This may not be a complete fix but I got stuck so I'm posting what > I have, which at least fixes the ICE.) > > We ICE on the simple: > > struct X { const X* x = this; }; > constexpr const X& x = X{}; > > where store_init_value initializes 'x' with > > &TARGET_EXPR <D.2768, {.x=(const struct X *) &<PLACEHOLDER_EXPR struct X>}> > > but we must lifetime-extend via extend_ref_init_temps and we get > > _ZGR1x_.x = (const struct X *) &<PLACEHOLDER_EXPR struct X> >>>;, (const struct X &) &_ZGR1x_; > > Since 'x' was declared constexpr, we do cxx_constant_init and we hit > the preeval code added in r269003 while evaluating the INIT_EXPR: > > _ZGR1x_.x = (const struct X *) &<PLACEHOLDER_EXPR struct X> >>> > > but we have no ctx.ctor or ctx.object here so lookup_placeholder won't > find anything that could replace X and we ICE on > 7861 /* A placeholder without a referent. We can get here when > 7862 checking whether NSDMIs are noexcept, or in massage_init_elt; > 7863 just say it's non-constant for now. */ > 7864 gcc_assert (ctx->quiet); > because cxx_constant_init means !ctx->quiet. It's not correct that > there isn't a referent. I think the following patch is a pretty > straightforward fix: pass the _ZGR var down to maybe_constant_init so > that it can replace the PLACEHOLDER_EXPR with _ZGR1x_. > > What I wasn't able to make work is the commented assert in the test. > It doesn't pass because we complain that _ZGR1x_ isn't a constexpr > variable, That sounds like we aren't (correctly) implementing https://eel.is/c++draft/expr.const#4.7 > but making it so would just result in "used in its own > initializer" (which is true). True, but not in the sense it means; its initializer doesn't depend on its (uninitialized) value. > I notice that while clang++ compiles > the assert fine, MSVC++/icc reject it as non-constant. So maybe we > don't have to/shouldn't make it work. > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? > > PR c++/107079 > > gcc/cp/ChangeLog: > > * call.cc (set_up_extended_ref_temp): Pass var to maybe_constant_init. > > gcc/testsuite/ChangeLog: > > * g++.dg/cpp0x/constexpr-nsdmi2.C: New test. > --- > gcc/cp/call.cc | 2 +- > gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C | 9 +++++++++ > 2 files changed, 10 insertions(+), 1 deletion(-) > create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C > > diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc > index f7c5d9da94b..a0afab9b26a 100644 > --- a/gcc/cp/call.cc > +++ b/gcc/cp/call.cc > @@ -13583,7 +13583,7 @@ set_up_extended_ref_temp (tree decl, tree expr, vec<tree, va_gc> **cleanups, > > /* If the initializer is constant, put it in DECL_INITIAL so we get > static initialization and use in constant expressions. */ > - init = maybe_constant_init (expr); > + init = maybe_constant_init (expr, var); We should also pass true for manifestly_const_eval as in store_init_value. > /* As in store_init_value. */ > init = cp_fully_fold (init); > if (TREE_CONSTANT (init)) > diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C > new file mode 100644 > index 00000000000..6dbb7eb739a > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C > @@ -0,0 +1,9 @@ > +// PR c++/107079 > +// { dg-do compile { target c++11 } } > + > +struct X { > + const X* x = this; > +}; > +constexpr const X& x = X{}; > +// TODO: Should the assert pass? > +//static_assert(x.x == &x); > > base-commit: 77bb54b1b07add45007c664724b726541d672ef3 ^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH v2] c++: ICE initing lifetime-extended constexpr var [PR107079] 2023-02-09 0:00 ` Jason Merrill @ 2023-02-09 2:15 ` Marek Polacek 2023-02-09 23:41 ` Jason Merrill 0 siblings, 1 reply; 4+ messages in thread From: Marek Polacek @ 2023-02-09 2:15 UTC (permalink / raw) To: Jason Merrill; +Cc: GCC Patches, Patrick Palka On Wed, Feb 08, 2023 at 04:00:25PM -0800, Jason Merrill wrote: > On 2/8/23 13:01, Marek Polacek wrote: > > (This may not be a complete fix but I got stuck so I'm posting what > > I have, which at least fixes the ICE.) > > > > We ICE on the simple: > > > > struct X { const X* x = this; }; > > constexpr const X& x = X{}; > > > > where store_init_value initializes 'x' with > > > > &TARGET_EXPR <D.2768, {.x=(const struct X *) &<PLACEHOLDER_EXPR struct X>}> > > > > but we must lifetime-extend via extend_ref_init_temps and we get > > > > _ZGR1x_.x = (const struct X *) &<PLACEHOLDER_EXPR struct X> >>>;, (const struct X &) &_ZGR1x_; > > > > Since 'x' was declared constexpr, we do cxx_constant_init and we hit > > the preeval code added in r269003 while evaluating the INIT_EXPR: > > > > _ZGR1x_.x = (const struct X *) &<PLACEHOLDER_EXPR struct X> >>> > > > > but we have no ctx.ctor or ctx.object here so lookup_placeholder won't > > find anything that could replace X and we ICE on > > 7861 /* A placeholder without a referent. We can get here when > > 7862 checking whether NSDMIs are noexcept, or in massage_init_elt; > > 7863 just say it's non-constant for now. */ > > 7864 gcc_assert (ctx->quiet); > > because cxx_constant_init means !ctx->quiet. It's not correct that > > there isn't a referent. I think the following patch is a pretty > > straightforward fix: pass the _ZGR var down to maybe_constant_init so > > that it can replace the PLACEHOLDER_EXPR with _ZGR1x_. > > > > What I wasn't able to make work is the commented assert in the test. > > It doesn't pass because we complain that _ZGR1x_ isn't a constexpr > > variable, > > That sounds like we aren't (correctly) implementing > > https://eel.is/c++draft/expr.const#4.7 Ah yes, this is DR2126 = c++/101588. I wonder if the fix will include checking startswith (IDENTIFIER_POINTER (DECL_NAME (variable)), "_ZGR") to see if its lifetime is extended. > > but making it so would just result in "used in its own > > initializer" (which is true). > > True, but not in the sense it means; its initializer doesn't depend on its > (uninitialized) value. ...because we're only interested in its address. > > diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc > > index f7c5d9da94b..a0afab9b26a 100644 > > --- a/gcc/cp/call.cc > > +++ b/gcc/cp/call.cc > > @@ -13583,7 +13583,7 @@ set_up_extended_ref_temp (tree decl, tree expr, vec<tree, va_gc> **cleanups, > > /* If the initializer is constant, put it in DECL_INITIAL so we get > > static initialization and use in constant expressions. */ > > - init = maybe_constant_init (expr); > > + init = maybe_constant_init (expr, var); > > We should also pass true for manifestly_const_eval as in store_init_value. Done. Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? -- >8 -- We ICE on the simple: struct X { const X* x = this; }; constexpr const X& x = X{}; where store_init_value initializes 'x' with &TARGET_EXPR <D.2768, {.x=(const struct X *) &<PLACEHOLDER_EXPR struct X>}> but we must lifetime-extend via extend_ref_init_temps and we get _ZGR1x_.x = (const struct X *) &<PLACEHOLDER_EXPR struct X> >>>;, (const struct X &) &_ZGR1x_; Since 'x' was declared constexpr, we do cxx_constant_init and we hit the preeval code added in r269003 while evaluating the INIT_EXPR: _ZGR1x_.x = (const struct X *) &<PLACEHOLDER_EXPR struct X> >>> but we have no ctx.ctor or ctx.object here so lookup_placeholder won't find anything that could replace X and we ICE on 7861 /* A placeholder without a referent. We can get here when 7862 checking whether NSDMIs are noexcept, or in massage_init_elt; 7863 just say it's non-constant for now. */ 7864 gcc_assert (ctx->quiet); because cxx_constant_init means !ctx->quiet. It's not correct that there isn't a referent. I think the following patch is a pretty straightforward fix: pass the _ZGR var down to maybe_constant_init so that it can replace the PLACEHOLDER_EXPR with _ZGR1x_. The commented assert in the test doesn't pass: we complain that _ZGR1x_ isn't a constexpr variable because we don't implement DR2126 (PR101588). PR c++/107079 gcc/cp/ChangeLog: * call.cc (set_up_extended_ref_temp): Pass var to maybe_constant_init. gcc/testsuite/ChangeLog: * g++.dg/cpp0x/constexpr-nsdmi2.C: New test. --- gcc/cp/call.cc | 2 +- gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C | 9 +++++++++ 2 files changed, 10 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc index f7c5d9da94b..a349d8e79db 100644 --- a/gcc/cp/call.cc +++ b/gcc/cp/call.cc @@ -13583,7 +13583,7 @@ set_up_extended_ref_temp (tree decl, tree expr, vec<tree, va_gc> **cleanups, /* If the initializer is constant, put it in DECL_INITIAL so we get static initialization and use in constant expressions. */ - init = maybe_constant_init (expr); + init = maybe_constant_init (expr, var, /*manifestly_const_eval=*/true); /* As in store_init_value. */ init = cp_fully_fold (init); if (TREE_CONSTANT (init)) diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C new file mode 100644 index 00000000000..d711b8051c0 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C @@ -0,0 +1,9 @@ +// PR c++/107079 +// { dg-do compile { target c++11 } } + +struct X { + const X* x = this; +}; +constexpr const X& x = X{}; +// TODO: The assert should pass once we implement DR2126 (c++/101588). +//static_assert(x.x == &x); base-commit: f6fc79d0c90ff3a924d272eff74b32656bdf5481 -- 2.39.1 ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] c++: ICE initing lifetime-extended constexpr var [PR107079] 2023-02-09 2:15 ` [PATCH v2] " Marek Polacek @ 2023-02-09 23:41 ` Jason Merrill 0 siblings, 0 replies; 4+ messages in thread From: Jason Merrill @ 2023-02-09 23:41 UTC (permalink / raw) To: Marek Polacek; +Cc: GCC Patches, Patrick Palka On 2/8/23 18:15, Marek Polacek wrote: > On Wed, Feb 08, 2023 at 04:00:25PM -0800, Jason Merrill wrote: >> On 2/8/23 13:01, Marek Polacek wrote: >>> (This may not be a complete fix but I got stuck so I'm posting what >>> I have, which at least fixes the ICE.) >>> >>> We ICE on the simple: >>> >>> struct X { const X* x = this; }; >>> constexpr const X& x = X{}; >>> >>> where store_init_value initializes 'x' with >>> >>> &TARGET_EXPR <D.2768, {.x=(const struct X *) &<PLACEHOLDER_EXPR struct X>}> >>> >>> but we must lifetime-extend via extend_ref_init_temps and we get >>> >>> _ZGR1x_.x = (const struct X *) &<PLACEHOLDER_EXPR struct X> >>>;, (const struct X &) &_ZGR1x_; >>> >>> Since 'x' was declared constexpr, we do cxx_constant_init and we hit >>> the preeval code added in r269003 while evaluating the INIT_EXPR: >>> >>> _ZGR1x_.x = (const struct X *) &<PLACEHOLDER_EXPR struct X> >>> >>> >>> but we have no ctx.ctor or ctx.object here so lookup_placeholder won't >>> find anything that could replace X and we ICE on >>> 7861 /* A placeholder without a referent. We can get here when >>> 7862 checking whether NSDMIs are noexcept, or in massage_init_elt; >>> 7863 just say it's non-constant for now. */ >>> 7864 gcc_assert (ctx->quiet); >>> because cxx_constant_init means !ctx->quiet. It's not correct that >>> there isn't a referent. I think the following patch is a pretty >>> straightforward fix: pass the _ZGR var down to maybe_constant_init so >>> that it can replace the PLACEHOLDER_EXPR with _ZGR1x_. >>> >>> What I wasn't able to make work is the commented assert in the test. >>> It doesn't pass because we complain that _ZGR1x_ isn't a constexpr >>> variable, >> >> That sounds like we aren't (correctly) implementing >> >> https://eel.is/c++draft/expr.const#4.7 > > Ah yes, this is DR2126 = c++/101588. I wonder if the fix will include > checking startswith (IDENTIFIER_POINTER (DECL_NAME (variable)), "_ZGR") > to see if its lifetime is extended. > >>> but making it so would just result in "used in its own >>> initializer" (which is true). >> >> True, but not in the sense it means; its initializer doesn't depend on its >> (uninitialized) value. > > ...because we're only interested in its address. > >>> diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc >>> index f7c5d9da94b..a0afab9b26a 100644 >>> --- a/gcc/cp/call.cc >>> +++ b/gcc/cp/call.cc >>> @@ -13583,7 +13583,7 @@ set_up_extended_ref_temp (tree decl, tree expr, vec<tree, va_gc> **cleanups, >>> /* If the initializer is constant, put it in DECL_INITIAL so we get >>> static initialization and use in constant expressions. */ >>> - init = maybe_constant_init (expr); >>> + init = maybe_constant_init (expr, var); >> >> We should also pass true for manifestly_const_eval as in store_init_value. > > Done. > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? OK. > -- >8 -- > We ICE on the simple: > > struct X { const X* x = this; }; > constexpr const X& x = X{}; > > where store_init_value initializes 'x' with > > &TARGET_EXPR <D.2768, {.x=(const struct X *) &<PLACEHOLDER_EXPR struct X>}> > > but we must lifetime-extend via extend_ref_init_temps and we get > > _ZGR1x_.x = (const struct X *) &<PLACEHOLDER_EXPR struct X> >>>;, (const struct X &) &_ZGR1x_; > > Since 'x' was declared constexpr, we do cxx_constant_init and we hit > the preeval code added in r269003 while evaluating the INIT_EXPR: > > _ZGR1x_.x = (const struct X *) &<PLACEHOLDER_EXPR struct X> >>> > > but we have no ctx.ctor or ctx.object here so lookup_placeholder won't > find anything that could replace X and we ICE on > 7861 /* A placeholder without a referent. We can get here when > 7862 checking whether NSDMIs are noexcept, or in massage_init_elt; > 7863 just say it's non-constant for now. */ > 7864 gcc_assert (ctx->quiet); > because cxx_constant_init means !ctx->quiet. It's not correct that > there isn't a referent. I think the following patch is a pretty > straightforward fix: pass the _ZGR var down to maybe_constant_init so > that it can replace the PLACEHOLDER_EXPR with _ZGR1x_. > > The commented assert in the test doesn't pass: we complain that _ZGR1x_ > isn't a constexpr variable because we don't implement DR2126 (PR101588). > > PR c++/107079 > > gcc/cp/ChangeLog: > > * call.cc (set_up_extended_ref_temp): Pass var to maybe_constant_init. > > gcc/testsuite/ChangeLog: > > * g++.dg/cpp0x/constexpr-nsdmi2.C: New test. > --- > gcc/cp/call.cc | 2 +- > gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C | 9 +++++++++ > 2 files changed, 10 insertions(+), 1 deletion(-) > create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C > > diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc > index f7c5d9da94b..a349d8e79db 100644 > --- a/gcc/cp/call.cc > +++ b/gcc/cp/call.cc > @@ -13583,7 +13583,7 @@ set_up_extended_ref_temp (tree decl, tree expr, vec<tree, va_gc> **cleanups, > > /* If the initializer is constant, put it in DECL_INITIAL so we get > static initialization and use in constant expressions. */ > - init = maybe_constant_init (expr); > + init = maybe_constant_init (expr, var, /*manifestly_const_eval=*/true); > /* As in store_init_value. */ > init = cp_fully_fold (init); > if (TREE_CONSTANT (init)) > diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C > new file mode 100644 > index 00000000000..d711b8051c0 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C > @@ -0,0 +1,9 @@ > +// PR c++/107079 > +// { dg-do compile { target c++11 } } > + > +struct X { > + const X* x = this; > +}; > +constexpr const X& x = X{}; > +// TODO: The assert should pass once we implement DR2126 (c++/101588). > +//static_assert(x.x == &x); > > base-commit: f6fc79d0c90ff3a924d272eff74b32656bdf5481 ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2023-02-09 23:41 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2023-02-08 21:01 [PATCH] c++: ICE initing lifetime-extended constexpr var [PR107079] Marek Polacek 2023-02-09 0:00 ` Jason Merrill 2023-02-09 2:15 ` [PATCH v2] " Marek Polacek 2023-02-09 23:41 ` Jason Merrill
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