[v2] libstdc++: Hide 128-bit int and float types behind handle for basic_format_arg visitation [PR108053]
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Commit Message
Implement visit_format_arg and basic_format_arg::visit function,
in terms of _M_visit_user member functions, that wraps any type
stored inside basic_format_arg, that is not specified as standard
into the handle. This affects __in128, unsigned __in128,
PowerPC specific __iee128 and __ibm128, and _Float128 for architectures
where long double is not 128bits.
The bfloat16, _Float16, _Float32, _Float32, and _Float128 for
128bits long double are not are not addressed, as they
are transformed into standard floating point types.
For internal purposes __format::__visit_format_arg function is
used, that provides an umodifed access to stored object.
PR libstdc++/108053
libstdc++-v3/ChangeLog:
* include/std/format (basic_format_arg::_M_visit_user):
Helper function for wrapping extension types into handle
(visit_format_arg): Call `_M_visit_user` instead of `_M_visit`.
(basic_format_arg::visit): As above.
(__format::__visit_format_arg): Provides direct access to
values stored in basic_format_arg.
(__format::__int_from_arg): Use __format::__visit_format_arg
instead of std::visit_format_arg.
(_Formatting_scanner::_M_format_arg): As above.
(_Checking_scanner::__do_vformat_to): As above.
* testsuite/std/format/arguments/args.cc: New tests.
* testsuite/std/format/string.cc: Test for using __int128
as width/precision.
---
Revision added missing decltype(auto) return type for lambda in _M_user_visit.
Tested on x84_64-linux. Tested arguments/args.cc` with -mlong-double-128.
Tested `std/format` test on ppc64le-linux, with both -mabi=ieeelongdouble and -mabi=ibmlongdouble.
OK for trunk?
libstdc++-v3/include/std/format | 49 +++++++++++--
.../testsuite/std/format/arguments/args.cc | 73 +++++++++++++++++++
libstdc++-v3/testsuite/std/format/string.cc | 10 ++-
3 files changed, 123 insertions(+), 9 deletions(-)
Comments
On 12/03/25 15:39 +0100, Tomasz Kamiński wrote:
>Implement visit_format_arg and basic_format_arg::visit function,
>in terms of _M_visit_user member functions, that wraps any type
>stored inside basic_format_arg, that is not specified as standard
>into the handle. This affects __in128, unsigned __in128,
Spelling: __int128 (both times)
>PowerPC specific __iee128 and __ibm128, and _Float128 for architectures
__ieee128
>where long double is not 128bits.
>
>The bfloat16, _Float16, _Float32, _Float32, and _Float128 for
>128bits long double are not are not addressed, as they
>are transformed into standard floating point types.
>
>For internal purposes __format::__visit_format_arg function is
>used, that provides an umodifed access to stored object.
unmodified
>
> PR libstdc++/108053
>
>libstdc++-v3/ChangeLog:
>
> * include/std/format (basic_format_arg::_M_visit_user):
> Helper function for wrapping extension types into handle
Missing '.' at the end of the sentence.
> (visit_format_arg): Call `_M_visit_user` instead of `_M_visit`.
> (basic_format_arg::visit): As above.
> (__format::__visit_format_arg): Provides direct access to
> values stored in basic_format_arg.
> (__format::__int_from_arg): Use __format::__visit_format_arg
> instead of std::visit_format_arg.
> (_Formatting_scanner::_M_format_arg): As above.
> (_Checking_scanner::__do_vformat_to): As above.
> * testsuite/std/format/arguments/args.cc: New tests.
> * testsuite/std/format/string.cc: Test for using __int128
> as width/precision.
>---
>Revision added missing decltype(auto) return type for lambda in _M_user_visit.
>Tested on x84_64-linux. Tested arguments/args.cc` with -mlong-double-128.
>Tested `std/format` test on ppc64le-linux, with both -mabi=ieeelongdouble and -mabi=ibmlongdouble.
>OK for trunk?
Some more minor comments below, mostly typos in comments, but one
small change to _M_visit_user.
OK for trunk with those changes, thanks.
> libstdc++-v3/include/std/format | 49 +++++++++++--
> .../testsuite/std/format/arguments/args.cc | 73 +++++++++++++++++++
> libstdc++-v3/testsuite/std/format/string.cc | 10 ++-
> 3 files changed, 123 insertions(+), 9 deletions(-)
>
>diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format
>index e7e0d2d142b..5085658cdb7 100644
>--- a/libstdc++-v3/include/std/format
>+++ b/libstdc++-v3/include/std/format
>@@ -3290,10 +3290,12 @@ namespace __format
> template<typename _Context, typename... _Args>
> class _Arg_store;
>
>+ template<typename _Visitor, typename _Ctx>
>+ decltype(auto) __visit_format_arg(_Visitor&&, basic_format_arg<_Ctx>);
>+
> template<typename _Ch, typename _Tp>
> consteval _Arg_t
> __to_arg_t_enum() noexcept;
>-
> } // namespace __format
> /// @endcond
>
>@@ -3365,12 +3367,12 @@ namespace __format
> template<typename _Visitor>
> decltype(auto)
> visit(this basic_format_arg __arg, _Visitor&& __vis)
>- { return __arg._M_visit(std::forward<_Visitor>(__vis), __arg._M_type); }
>+ { return __arg._M_visit_user(std::forward<_Visitor>(__vis), __arg._M_type); }
>
> template<typename _Res, typename _Visitor>
> _Res
> visit(this basic_format_arg __arg, _Visitor&& __vis)
>- { return __arg._M_visit(std::forward<_Visitor>(__vis), __arg._M_type); }
>+ { return __arg._M_visit_user(std::forward<_Visitor>(__vis), __arg._M_type); }
> #endif
>
> private:
>@@ -3587,6 +3589,10 @@ namespace __format
> friend decltype(auto)
> visit_format_arg(_Visitor&& __vis, basic_format_arg<_Ctx>);
>
>+ template<typename _Visitor, typename _Ctx>
>+ friend decltype(auto)
>+ __format::__visit_format_arg(_Visitor&&, basic_format_arg<_Ctx>);
>+
> template<typename _Ch, typename _Tp>
> friend consteval __format::_Arg_t
> __format::__to_arg_t_enum() noexcept;
>@@ -3655,6 +3661,28 @@ namespace __format
> __builtin_unreachable();
> }
> }
>+
>+ template<typename _Visitor>
>+ decltype(auto)
>+ _M_visit_user(_Visitor&& __vis, __format::_Arg_t __type)
>+ {
>+ return _M_visit([&__vis]<typename _Tp>(_Tp& __val) -> decltype(auto)
>+ {
>+ constexpr bool __user_facing = __is_one_of<_Tp,
>+ monostate, bool, _CharT,
I think the only way it's possible to get a monostate here is for a
default constructed format arg, and visiting that is probably a
mistake. So let's put monostate at the end of this list, otherwise every
time we evaluate this __is_one_of check the first instantiation is
is_same<_Tp, monostate> which will fail nearly every time.
>+ int, unsigned int, long long int, unsigned long long int,
>+ float, double, long double,
>+ const _CharT*, basic_string_view<_CharT>,
>+ const void*, handle>::value;
>+ if constexpr (__user_facing)
>+ return std::forward<_Visitor>(__vis)(__val);
>+ else
>+ {
>+ handle __h(__val);
>+ return std::forward<_Visitor>(__vis)(__h);
>+ }
>+ }, __type);
>+ }
> };
>
> template<typename _Visitor, typename _Context>
>@@ -3662,12 +3690,19 @@ namespace __format
> inline decltype(auto)
> visit_format_arg(_Visitor&& __vis, basic_format_arg<_Context> __arg)
> {
>- return __arg._M_visit(std::forward<_Visitor>(__vis), __arg._M_type);
>+ return __arg._M_visit_user(std::forward<_Visitor>(__vis), __arg._M_type);
> }
>
> /// @cond undocumented
> namespace __format
> {
>+ template<typename _Visitor, typename _Ctx>
>+ inline decltype(auto)
>+ __visit_format_arg(_Visitor&& __vis, basic_format_arg<_Ctx> __arg)
>+ {
>+ return __arg._M_visit(std::forward<_Visitor>(__vis), __arg._M_type);
>+ }
>+
> struct _WidthPrecVisitor
> {
> template<typename _Tp>
>@@ -3699,7 +3734,7 @@ namespace __format
> template<typename _Context>
> inline size_t
> __int_from_arg(const basic_format_arg<_Context>& __arg)
>- { return std::visit_format_arg(_WidthPrecVisitor(), __arg); }
>+ { return __format::__visit_format_arg(_WidthPrecVisitor(), __arg); }
>
> // Pack _Arg_t enum values into a single 60-bit integer.
> template<int _Bits, size_t _Nm>
>@@ -4152,7 +4187,7 @@ namespace __format
> using _Context = basic_format_context<_Out, _CharT>;
> using handle = typename basic_format_arg<_Context>::handle;
>
>- std::visit_format_arg([this](auto& __arg) {
>+ __format::__visit_format_arg([this](auto& __arg) {
> using _Type = remove_reference_t<decltype(__arg)>;
> using _Formatter = typename _Context::template formatter_type<_Type>;
> if constexpr (is_same_v<_Type, monostate>)
>@@ -4254,7 +4289,7 @@ namespace __format
> if (__fmt.size() == 2 && __fmt[0] == '{' && __fmt[1] == '}')
> {
> bool __done = false;
>- std::visit_format_arg([&](auto& __arg) {
>+ __format::__visit_format_arg([&](auto& __arg) {
> using _Tp = remove_cvref_t<decltype(__arg)>;
> if constexpr (is_same_v<_Tp, bool>)
> {
>diff --git a/libstdc++-v3/testsuite/std/format/arguments/args.cc b/libstdc++-v3/testsuite/std/format/arguments/args.cc
>index 2cea0a1b63f..8379528a3dd 100644
>--- a/libstdc++-v3/testsuite/std/format/arguments/args.cc
>+++ b/libstdc++-v3/testsuite/std/format/arguments/args.cc
>@@ -148,9 +148,82 @@ test_member_visit()
> #endif
> }
>
>+template<typename T>
>+void test_visited_as_handle()
>+{
>+ T v{};
>+ auto store = std::make_format_args(v);
>+ std::format_args args = store;
>+
>+ constexpr auto is_handle = [](auto arg) {
>+ return std::is_same_v<decltype(arg), decltype(args.get(0))::handle>;
>+ };
>+ VERIFY( std::visit_format_arg(is_handle, args.get(0)) );
>+#if __cpp_lib_format >= 202306L // C++26 adds std::basic_format_arg::visit
>+ VERIFY( args.get(0).visit(is_handle) );
>+#endif
>+}
>+
>+template<typename E, typename S>
>+void test_visited_as()
>+{
>+ auto v = static_cast<S>(1.0);
>+ auto store = std::make_format_args(v);
>+ std::format_args args = store;
>+
>+ auto is_expected_val = [v](auto arg) {
>+ if constexpr (std::is_same_v<decltype(arg), E>)
>+ return arg == static_cast<E>(v);
>+ return false;
>+ };
>+ VERIFY( std::visit_format_arg(is_expected_val, args.get(0)) );
>+#if __cpp_lib_format >= 202306L // C++26 adds std::basic_format_arg::visit
>+ VERIFY( args.get(0).visit(is_expected_val) );
>+#endif
>+}
>+
>+template<typename T>
>+concept can_format = std::is_default_constructible_v<std::formatter<T, char>>;
>+
> int main()
> {
> test_empty();
> test_args();
> test_member_visit();
>+
>+#ifdef __SIZEOF_INT128__
>+ test_visited_as_handle<__int128>();
>+ test_visited_as_handle<unsigned __int128>();
>+#endif
>+// TODO: This should be passed visited as handle.
>+#ifdef __STDCPP_FLOAT16_T__
>+ if constexpr (can_format<_Float16>)
>+ test_visited_as<float, _Float16>();
>+#endif
>+#ifdef __STDCPP_BFLOAT16_T__
>+ if constexpr (can_format<__gnu_cxx::__bfloat16_t>)
>+ test_visited_as<float, __gnu_cxx::__bfloat16_t>();
>+#endif
>+#ifdef __FLT32_DIG__
>+ if constexpr (can_format<_Float32>)
>+ test_visited_as<float, _Float32>();
>+#endif
>+#ifdef __FLT64_DIG__
>+ if constexpr (can_format<_Float64>)
>+ test_visited_as<double, _Float64>();
>+#endif
>+#ifdef __FLT128_DIG__
>+ if constexpr (can_format<_Float128>)
>+# ifdef _GLIBCXX_LDOUBLE_IS_IEEE_BINARY128
>+ test_visited_as<long double, _Float128>();
>+# else
>+ test_visited_as_handle<_Float128>();
>+# endif
>+#endif
>+#ifdef _GLIBCXX_LONG_DOUBLE_ALT128_COMPAT
>+ if constexpr (!std::is_same_v<__ieee128, long double>)
>+ test_visited_as_handle<__ieee128>();
>+ if constexpr (!std::is_same_v<__ibm128, long double>)
>+ test_visited_as_handle<__ibm128>();
>+#endif
> }
>diff --git a/libstdc++-v3/testsuite/std/format/string.cc b/libstdc++-v3/testsuite/std/format/string.cc
>index d5f30500139..0933639faf0 100644
>--- a/libstdc++-v3/testsuite/std/format/string.cc
>+++ b/libstdc++-v3/testsuite/std/format/string.cc
>@@ -113,11 +113,14 @@ test_format_spec()
> VERIFY( ! is_format_string_for("{:0c}", 'c') );
> VERIFY( ! is_format_string_for("{:0s}", true) );
>
>- // Dynamic width arg must be an integer type.
>+ // Dynamic width arg must be an standar integer type.
"an standar" -> "a standard"
> VERIFY( ! is_format_string_for("{:{}d}", 1, 1.5) );
> VERIFY( ! is_format_string_for("{:{}d}", 1, true) );
> VERIFY( ! is_format_string_for("{:{}d}", 1, "str") );
> VERIFY( ! is_format_string_for("{:{}d}", 1, nullptr) );
>+#ifdef __SIZEOF_INT128__
>+ VERIFY( ! is_format_string_for("{:{}d}", 1, static_cast<__int128>(1)) );
>+#endif
>
> // Precision only valid for string and floating-point types.
> VERIFY( ! is_format_string_for("{:.3d}", 1) );
>@@ -126,11 +129,14 @@ test_format_spec()
> VERIFY( ! is_format_string_for("{:3.3s}", 'c') );
> VERIFY( ! is_format_string_for("{:3.3p}", nullptr) );
>
>- // Dynamic precision arg must be an integer type.
>+ // Dynamic precision arg must be an standard integer type.
"an" -> "a"
> VERIFY( ! is_format_string_for("{:.{}f}", 1.0, 1.5) );
> VERIFY( ! is_format_string_for("{:.{}f}", 1.0, true) );
> VERIFY( ! is_format_string_for("{:.{}f}", 1.0, "str") );
> VERIFY( ! is_format_string_for("{:.{}f}", 1.0, nullptr) );
>+#ifdef __SIZEOF_INT128__
>+ VERIFY( ! is_format_string_for("{:{}f}", 1.0, static_cast<unsigned __int128>(1)) );
>+#endif
>
> // Invalid presentation types for integers.
> VERIFY( ! is_format_string_for("{:f}", 1) );
>--
>2.48.1
>
@@ -3290,10 +3290,12 @@ namespace __format
template<typename _Context, typename... _Args>
class _Arg_store;
+ template<typename _Visitor, typename _Ctx>
+ decltype(auto) __visit_format_arg(_Visitor&&, basic_format_arg<_Ctx>);
+
template<typename _Ch, typename _Tp>
consteval _Arg_t
__to_arg_t_enum() noexcept;
-
} // namespace __format
/// @endcond
@@ -3365,12 +3367,12 @@ namespace __format
template<typename _Visitor>
decltype(auto)
visit(this basic_format_arg __arg, _Visitor&& __vis)
- { return __arg._M_visit(std::forward<_Visitor>(__vis), __arg._M_type); }
+ { return __arg._M_visit_user(std::forward<_Visitor>(__vis), __arg._M_type); }
template<typename _Res, typename _Visitor>
_Res
visit(this basic_format_arg __arg, _Visitor&& __vis)
- { return __arg._M_visit(std::forward<_Visitor>(__vis), __arg._M_type); }
+ { return __arg._M_visit_user(std::forward<_Visitor>(__vis), __arg._M_type); }
#endif
private:
@@ -3587,6 +3589,10 @@ namespace __format
friend decltype(auto)
visit_format_arg(_Visitor&& __vis, basic_format_arg<_Ctx>);
+ template<typename _Visitor, typename _Ctx>
+ friend decltype(auto)
+ __format::__visit_format_arg(_Visitor&&, basic_format_arg<_Ctx>);
+
template<typename _Ch, typename _Tp>
friend consteval __format::_Arg_t
__format::__to_arg_t_enum() noexcept;
@@ -3655,6 +3661,28 @@ namespace __format
__builtin_unreachable();
}
}
+
+ template<typename _Visitor>
+ decltype(auto)
+ _M_visit_user(_Visitor&& __vis, __format::_Arg_t __type)
+ {
+ return _M_visit([&__vis]<typename _Tp>(_Tp& __val) -> decltype(auto)
+ {
+ constexpr bool __user_facing = __is_one_of<_Tp,
+ monostate, bool, _CharT,
+ int, unsigned int, long long int, unsigned long long int,
+ float, double, long double,
+ const _CharT*, basic_string_view<_CharT>,
+ const void*, handle>::value;
+ if constexpr (__user_facing)
+ return std::forward<_Visitor>(__vis)(__val);
+ else
+ {
+ handle __h(__val);
+ return std::forward<_Visitor>(__vis)(__h);
+ }
+ }, __type);
+ }
};
template<typename _Visitor, typename _Context>
@@ -3662,12 +3690,19 @@ namespace __format
inline decltype(auto)
visit_format_arg(_Visitor&& __vis, basic_format_arg<_Context> __arg)
{
- return __arg._M_visit(std::forward<_Visitor>(__vis), __arg._M_type);
+ return __arg._M_visit_user(std::forward<_Visitor>(__vis), __arg._M_type);
}
/// @cond undocumented
namespace __format
{
+ template<typename _Visitor, typename _Ctx>
+ inline decltype(auto)
+ __visit_format_arg(_Visitor&& __vis, basic_format_arg<_Ctx> __arg)
+ {
+ return __arg._M_visit(std::forward<_Visitor>(__vis), __arg._M_type);
+ }
+
struct _WidthPrecVisitor
{
template<typename _Tp>
@@ -3699,7 +3734,7 @@ namespace __format
template<typename _Context>
inline size_t
__int_from_arg(const basic_format_arg<_Context>& __arg)
- { return std::visit_format_arg(_WidthPrecVisitor(), __arg); }
+ { return __format::__visit_format_arg(_WidthPrecVisitor(), __arg); }
// Pack _Arg_t enum values into a single 60-bit integer.
template<int _Bits, size_t _Nm>
@@ -4152,7 +4187,7 @@ namespace __format
using _Context = basic_format_context<_Out, _CharT>;
using handle = typename basic_format_arg<_Context>::handle;
- std::visit_format_arg([this](auto& __arg) {
+ __format::__visit_format_arg([this](auto& __arg) {
using _Type = remove_reference_t<decltype(__arg)>;
using _Formatter = typename _Context::template formatter_type<_Type>;
if constexpr (is_same_v<_Type, monostate>)
@@ -4254,7 +4289,7 @@ namespace __format
if (__fmt.size() == 2 && __fmt[0] == '{' && __fmt[1] == '}')
{
bool __done = false;
- std::visit_format_arg([&](auto& __arg) {
+ __format::__visit_format_arg([&](auto& __arg) {
using _Tp = remove_cvref_t<decltype(__arg)>;
if constexpr (is_same_v<_Tp, bool>)
{
@@ -148,9 +148,82 @@ test_member_visit()
#endif
}
+template<typename T>
+void test_visited_as_handle()
+{
+ T v{};
+ auto store = std::make_format_args(v);
+ std::format_args args = store;
+
+ constexpr auto is_handle = [](auto arg) {
+ return std::is_same_v<decltype(arg), decltype(args.get(0))::handle>;
+ };
+ VERIFY( std::visit_format_arg(is_handle, args.get(0)) );
+#if __cpp_lib_format >= 202306L // C++26 adds std::basic_format_arg::visit
+ VERIFY( args.get(0).visit(is_handle) );
+#endif
+}
+
+template<typename E, typename S>
+void test_visited_as()
+{
+ auto v = static_cast<S>(1.0);
+ auto store = std::make_format_args(v);
+ std::format_args args = store;
+
+ auto is_expected_val = [v](auto arg) {
+ if constexpr (std::is_same_v<decltype(arg), E>)
+ return arg == static_cast<E>(v);
+ return false;
+ };
+ VERIFY( std::visit_format_arg(is_expected_val, args.get(0)) );
+#if __cpp_lib_format >= 202306L // C++26 adds std::basic_format_arg::visit
+ VERIFY( args.get(0).visit(is_expected_val) );
+#endif
+}
+
+template<typename T>
+concept can_format = std::is_default_constructible_v<std::formatter<T, char>>;
+
int main()
{
test_empty();
test_args();
test_member_visit();
+
+#ifdef __SIZEOF_INT128__
+ test_visited_as_handle<__int128>();
+ test_visited_as_handle<unsigned __int128>();
+#endif
+// TODO: This should be passed visited as handle.
+#ifdef __STDCPP_FLOAT16_T__
+ if constexpr (can_format<_Float16>)
+ test_visited_as<float, _Float16>();
+#endif
+#ifdef __STDCPP_BFLOAT16_T__
+ if constexpr (can_format<__gnu_cxx::__bfloat16_t>)
+ test_visited_as<float, __gnu_cxx::__bfloat16_t>();
+#endif
+#ifdef __FLT32_DIG__
+ if constexpr (can_format<_Float32>)
+ test_visited_as<float, _Float32>();
+#endif
+#ifdef __FLT64_DIG__
+ if constexpr (can_format<_Float64>)
+ test_visited_as<double, _Float64>();
+#endif
+#ifdef __FLT128_DIG__
+ if constexpr (can_format<_Float128>)
+# ifdef _GLIBCXX_LDOUBLE_IS_IEEE_BINARY128
+ test_visited_as<long double, _Float128>();
+# else
+ test_visited_as_handle<_Float128>();
+# endif
+#endif
+#ifdef _GLIBCXX_LONG_DOUBLE_ALT128_COMPAT
+ if constexpr (!std::is_same_v<__ieee128, long double>)
+ test_visited_as_handle<__ieee128>();
+ if constexpr (!std::is_same_v<__ibm128, long double>)
+ test_visited_as_handle<__ibm128>();
+#endif
}
@@ -113,11 +113,14 @@ test_format_spec()
VERIFY( ! is_format_string_for("{:0c}", 'c') );
VERIFY( ! is_format_string_for("{:0s}", true) );
- // Dynamic width arg must be an integer type.
+ // Dynamic width arg must be an standar integer type.
VERIFY( ! is_format_string_for("{:{}d}", 1, 1.5) );
VERIFY( ! is_format_string_for("{:{}d}", 1, true) );
VERIFY( ! is_format_string_for("{:{}d}", 1, "str") );
VERIFY( ! is_format_string_for("{:{}d}", 1, nullptr) );
+#ifdef __SIZEOF_INT128__
+ VERIFY( ! is_format_string_for("{:{}d}", 1, static_cast<__int128>(1)) );
+#endif
// Precision only valid for string and floating-point types.
VERIFY( ! is_format_string_for("{:.3d}", 1) );
@@ -126,11 +129,14 @@ test_format_spec()
VERIFY( ! is_format_string_for("{:3.3s}", 'c') );
VERIFY( ! is_format_string_for("{:3.3p}", nullptr) );
- // Dynamic precision arg must be an integer type.
+ // Dynamic precision arg must be an standard integer type.
VERIFY( ! is_format_string_for("{:.{}f}", 1.0, 1.5) );
VERIFY( ! is_format_string_for("{:.{}f}", 1.0, true) );
VERIFY( ! is_format_string_for("{:.{}f}", 1.0, "str") );
VERIFY( ! is_format_string_for("{:.{}f}", 1.0, nullptr) );
+#ifdef __SIZEOF_INT128__
+ VERIFY( ! is_format_string_for("{:{}f}", 1.0, static_cast<unsigned __int128>(1)) );
+#endif
// Invalid presentation types for integers.
VERIFY( ! is_format_string_for("{:f}", 1) );