From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 2181) id 185903858D35; Thu, 7 Mar 2024 20:56:01 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 185903858D35 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1709844961; bh=+rnt0cqh10RQbpnqbvij9he7aNjCppSbsZhv6ZC5fhI=; h=From:To:Subject:Date:From; b=ip1ecj6h8UkcBp+MhUSZqUcvhchZrSwqc+gPsGDSobvV7kioFHa92VCA6rqNLx3UE 6+4a0NM2kpvSZw/TZe8bVUFBnMI+x1iBElgBRH5f54NU8p2Vj1V8kMkeBiJxsRnV7s PM0I7UE8phyn70h2CH28Mnywz5NHdZEKxhFtItCY= MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Jonathan Wakely To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r14-9368] libstdc++: Better diagnostics for std::format errors X-Act-Checkin: gcc X-Git-Author: Jonathan Wakely X-Git-Refname: refs/heads/master X-Git-Oldrev: 0ed6e5b4820e01fa86b48a7b1d62f752ec97ea41 X-Git-Newrev: 24a2b5def06940f3f181418a439c408388f7eb56 Message-Id: <20240307205601.185903858D35@sourceware.org> Date: Thu, 7 Mar 2024 20:56:01 +0000 (GMT) List-Id: https://gcc.gnu.org/g:24a2b5def06940f3f181418a439c408388f7eb56 commit r14-9368-g24a2b5def06940f3f181418a439c408388f7eb56 Author: Jonathan Wakely Date: Thu Feb 29 16:13:13 2024 +0000 libstdc++: Better diagnostics for std::format errors This adds two new static_assert messages to the internals of std::make_format_args to give better diagnostics for invalid format args. Rather than just getting an error saying that basic_format_arg cannot be constructed, we get more specific errors for the cases where std::formatter isn't specialized for the type at all, and where it's specialized but only meets the BasicFormatter requirements and so can only format non-const arguments. Also add a test for the existing static_assert when constructing a format_string for non-formattable args. libstdc++-v3/ChangeLog: * include/std/format (_Arg_store::_S_make_elt): Add two static_assert checks to give more user-friendly error messages. * testsuite/lib/prune.exp (libstdc++-dg-prune): Prune another form of "in requirements with" note. * testsuite/std/format/arguments/args_neg.cc: Check for user-friendly diagnostics for non-formattable types. * testsuite/std/format/string_neg.cc: Likewise. Diff: --- libstdc++-v3/include/std/format | 13 +++++++++ libstdc++-v3/testsuite/lib/prune.exp | 1 + .../testsuite/std/format/arguments/args_neg.cc | 34 +++++++++++++++++++++- libstdc++-v3/testsuite/std/format/string_neg.cc | 4 +++ 4 files changed, 51 insertions(+), 1 deletion(-) diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format index ee189f9086c..1e839e88db4 100644 --- a/libstdc++-v3/include/std/format +++ b/libstdc++-v3/include/std/format @@ -3704,6 +3704,19 @@ namespace __format static _Element_t _S_make_elt(_Tp& __v) { + using _Tq = remove_const_t<_Tp>; + using _CharT = typename _Context::char_type; + static_assert(is_default_constructible_v>, + "std::formatter must be specialized for the type " + "of each format arg"); + using __format::__formattable_with; + if constexpr (is_const_v<_Tp>) + if constexpr (!__formattable_with<_Tp, _Context>) + if constexpr (__formattable_with<_Tq, _Context>) + static_assert(__formattable_with<_Tp, _Context>, + "format arg must be non-const because its " + "std::formatter specialization has a " + "non-const reference parameter"); basic_format_arg<_Context> __arg(__v); if constexpr (_S_values_only) return __arg._M_val; diff --git a/libstdc++-v3/testsuite/lib/prune.exp b/libstdc++-v3/testsuite/lib/prune.exp index 24a15ccad22..071dcf34c1e 100644 --- a/libstdc++-v3/testsuite/lib/prune.exp +++ b/libstdc++-v3/testsuite/lib/prune.exp @@ -54,6 +54,7 @@ proc libstdc++-dg-prune { system text } { regsub -all "(^|\n)\[^\n\]*: . skipping \[0-9\]* instantiation contexts \[^\n\]*" $text "" text regsub -all "(^|\n)\[^\n\]*: in .constexpr. expansion \[^\n\]*" $text "" text regsub -all "(^|\n)\[^\n\]*: in requirements .with\[^\n\]*" $text "" text + regsub -all "(^|\n)\[^\n\]*: in requirements with\[^\n\]*" $text "" text regsub -all "(^|\n) inlined from \[^\n\]*" $text "" text # Why doesn't GCC need these to strip header context? regsub -all "(^|\n)In file included from \[^\n\]*" $text "" text diff --git a/libstdc++-v3/testsuite/std/format/arguments/args_neg.cc b/libstdc++-v3/testsuite/std/format/arguments/args_neg.cc index 16ac3040146..ded56fe63ab 100644 --- a/libstdc++-v3/testsuite/std/format/arguments/args_neg.cc +++ b/libstdc++-v3/testsuite/std/format/arguments/args_neg.cc @@ -6,7 +6,39 @@ std::string rval() { return "path/etic/experience"; } -void f() +void test_rval() { (void)std::make_format_args(rval()); // { dg-error "cannot bind non-const lvalue reference" } } + +void test_missing_specialization() +{ + struct X { }; + X x; + (void)std::make_format_args(x); // { dg-error "here" } +// { dg-error "std::formatter must be specialized" "" { target *-*-* } 0 } +} + +struct Y { }; +template<> class std::formatter { +public: + constexpr typename format_parse_context::iterator + parse(format_parse_context& c) + { return c.begin(); } + + template + typename C::iterator format(Y&, C&) const; +}; + +void test(std::formatter& f, std::format_parse_context& pc) { + f.parse(pc); +} + +void test_const_arg() +{ + const Y y; + (void)std::make_format_args(y); // { dg-error "here" } +// { dg-error "format arg must be non-const" "" { target *-*-* } 0 } +} + +// { dg-prune-output "no matching function for call to .*::basic_format_arg<" } diff --git a/libstdc++-v3/testsuite/std/format/string_neg.cc b/libstdc++-v3/testsuite/std/format/string_neg.cc index 69bcc736cff..d5963145b18 100644 --- a/libstdc++-v3/testsuite/std/format/string_neg.cc +++ b/libstdc++-v3/testsuite/std/format/string_neg.cc @@ -4,3 +4,7 @@ auto s = std::format(" {9} "); // { dg-error "call to consteval function" } // { dg-error "invalid.arg.id" "" { target *-*-* } 0 } + +struct X { }; +std::format_string str(""); // dg-error "here" } +// { dg-error "std::formatter must be specialized" "" { target *-*-* } 0 }