Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for trunk and 15/14 after 15.2 is released?
-- >8 -- r13-3299 changed our internal declaration of __dynamic_cast to reside inside the abi / __cxxabiv1 namespace instead of the global namespace, matching the real declaration. This inadvertently made us now attempt constexpr evaluation of user-written calls to abi::__dynamic_cast since cxx_dynamic_cast_fn_p now also returns true for them, but we're not prepared to handle arbitrary calls to __dynamic_cast, and therefore ICE. This patch restores cxx_dynamic_cast_fn_p to return true only for synthesized calls to __dynamic_cast, which can be distinguished by DECL_ARTIFICIAL. PR c++/120620 gcc/cp/ChangeLog: * constexpr.cc (cxx_dynamic_cast_fn_p): Return true only for synthesized __dynamic_cast. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/constexpr-dynamic19.C: New test. --- gcc/cp/constexpr.cc | 6 +++++- gcc/testsuite/g++.dg/cpp2a/constexpr-dynamic19.C | 10 ++++++++++ 2 files changed, 15 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/cpp2a/constexpr-dynamic19.C diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc index e051a50fe16e..4cf94afb9ca5 100644 --- a/gcc/cp/constexpr.cc +++ b/gcc/cp/constexpr.cc @@ -3240,7 +3240,11 @@ cxx_dynamic_cast_fn_p (tree fndecl) { return (cxx_dialect >= cxx20 && id_equal (DECL_NAME (fndecl), "__dynamic_cast") - && CP_DECL_CONTEXT (fndecl) == abi_node); + && CP_DECL_CONTEXT (fndecl) == abi_node + /* Only consider implementation-detail __dynamic_cast calls that + correspond to an actual dynamic_cast, and ignore direct calls + to abi::__dynamic_cast. */ + && DECL_ARTIFICIAL (fndecl)); } /* Often, we have an expression in the form of address + offset, e.g. diff --git a/gcc/testsuite/g++.dg/cpp2a/constexpr-dynamic19.C b/gcc/testsuite/g++.dg/cpp2a/constexpr-dynamic19.C new file mode 100644 index 000000000000..27d167cebc35 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/constexpr-dynamic19.C @@ -0,0 +1,10 @@ +// PR c++/120620 +// { dg-do compile } + +#include <cxxabi.h> + +struct A* a; + +void f() { + void* const p = abi::__dynamic_cast(&a, 0, 0, 42); +} -- 2.50.1.469.ge813a0200a