On 8/1/25 11:16 AM, Patrick Palka wrote:
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));
With this patch, does constexpr dynamic_cast still work after including cxxabi.h?
Jason
