(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