On 1/19/22 11:15, Patrick Palka wrote:
Here we're emitting a bogus error during ahead of time evaluation of a non-dependent immediate member function call such as a.f(args) because the defacto templated form for such a call is (a.f)(args) but we're trying to evaluate it using the intermediate CALL_EXPR built by build_over_call, which has the non-member form f(a, args). The defacto member form is built in build_new_method_call, so it seems we should handle the immediate call there instead.
Hmm, there's already a bunch of code in build_over_call to try to fix up the object argument, and there seem to be many places other than build_new_method_call that call build_over_call for member functions; I think it's probably better to build the needed COMPONENT_REF in build_over_call.
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for trunk and perhaps 11? PR c++/99895 gcc/cp/ChangeLog: * call.cc (build_over_call): Don't evaluate non-dependent immediate member function calls here. (build_new_method_call): Instead evaluate them here. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/consteval-memfn1.C: New test. * g++.dg/cpp2a/consteval-memfn2.C: New test. --- gcc/cp/call.cc | 9 ++++- gcc/testsuite/g++.dg/cpp2a/consteval-memfn1.C | 15 ++++++++ gcc/testsuite/g++.dg/cpp2a/consteval-memfn2.C | 34 +++++++++++++++++++ 3 files changed, 57 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/cpp2a/consteval-memfn1.C create mode 100644 gcc/testsuite/g++.dg/cpp2a/consteval-memfn2.C diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc index d4a07a7a9b3..0583cc0083b 100644 --- a/gcc/cp/call.cc +++ b/gcc/cp/call.cc @@ -9241,7 +9241,10 @@ build_over_call (struct z_candidate *cand, int flags, tsubst_flags_t complain) addr, nargs, argarray); if (TREE_THIS_VOLATILE (fn) && cfun) current_function_returns_abnormally = 1; - if (immediate_invocation_p (fn, nargs)) + if (!DECL_FUNCTION_MEMBER_P (fn) + /* Non-dependent immediate member function calls are evaluated in + build_new_method_call. */ + && immediate_invocation_p (fn, nargs)) { tree obj_arg = NULL_TREE, exprimm = expr; if (DECL_CONSTRUCTOR_P (fn)) @@ -11227,6 +11230,10 @@ skip_prune: call = convert_from_reference (call); if (cast_to_void) call = build_nop (void_type_node, call); + + if (immediate_invocation_p (fn, vec_safe_length (orig_args))) + fold_non_dependent_expr (call, complain, + /*manifestly_const_eval=*/true); }/* Free all the conversions we allocated. */diff --git a/gcc/testsuite/g++.dg/cpp2a/consteval-memfn1.C b/gcc/testsuite/g++.dg/cpp2a/consteval-memfn1.C new file mode 100644 index 00000000000..d2df2e9b5ae --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/consteval-memfn1.C @@ -0,0 +1,15 @@ +// PR c++/99895 +// { dg-do compile { target c++20 } } + +struct fixed_string { + consteval int size(int n) const { + if (n < 0) throw; // { dg-error "not a constant" } + return n; + } +}; + +template<class> +void VerifyHash(fixed_string s) { + s.size(0); // { dg-bogus "" } + s.size(-1); // { dg-message "expansion of" } +} diff --git a/gcc/testsuite/g++.dg/cpp2a/consteval-memfn2.C b/gcc/testsuite/g++.dg/cpp2a/consteval-memfn2.C new file mode 100644 index 00000000000..71748f46b13 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/consteval-memfn2.C @@ -0,0 +1,34 @@ +// PR c++/99895 +// { dg-do compile { target c++20 } } + +static constexpr unsigned hash(const char* s, unsigned length) +{ + s=s; + return length; +} +template<unsigned N> +struct fixed_string +{ + constexpr fixed_string(const char (&s)[N]) + { + for (int i = 0; i < N; i++) + str[i] = s[i]; + } + consteval const char* data() const { return str; } + consteval unsigned size() const { return N-1; } + char str[N]; +}; +template<unsigned expected_hash, fixed_string... s> +static consteval void VerifyHash() +{ + ( + [](auto){static_assert(hash(s.data(), s.size()) == expected_hash);}(s) + ,...); + // The compiler mistakenly translates s.data() into s.data(&s) + // and then complains that the call is not valid, because + // the function expects 0 parameters and 1 "was provided". +} +void foo() +{ + VerifyHash<5, "khaki", "plums">(); +}
