[gcc r14-4799] libstdc++: add casts to from_chars in <charconv> [PR111883]

[Marek Polacek]

https://gcc.gnu.org/g:1d9263f292c3efc4e37c3a88117388e86d19b954

commit r14-4799-g1d9263f292c3efc4e37c3a88117388e86d19b954
Author: Marek Polacek <polacek@redhat.com>
Date:   Thu Oct 19 17:48:44 2023 -0400

    libstdc++: add casts to from_chars in <charconv> [PR111883]
    
    This fixes
    
    .../charconv: In function 'std::from_chars_result std::from_chars(const char*, const char*, _Float16&, chars_format)':
    .../charconv:687:17: warning: converting to '_Float16' from 'float' with greater conversion rank
      687 |       __value = __val;
          |                 ^~~~~
    .../charconv: In function 'std::from_chars_result std::from_chars(const char*, const char*, __gnu_cxx::__bfloat16_t&, chars_format)':
    .../charconv:763:17: warning: converting to '__gnu_cxx::__bfloat16_t' {aka '__bf16'} from 'float' with greater conversion rank
      763 |       __value = __val;
          |                 ^~~~~
    
    which was breaking a test:
    
    FAIL: g++.dg/warn/Wstringop-overflow-6.C  -std=gnu++26 (test for excess errors)
    
            PR testsuite/111883
    
    libstdc++-v3/ChangeLog:
    
            * include/std/charconv (from_chars): Add explicit casts.

Diff:
---
 libstdc++-v3/include/std/charconv | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/libstdc++-v3/include/std/charconv b/libstdc++-v3/include/std/charconv
index cb428fe6d3b7..6cb7fecff870 100644
--- a/libstdc++-v3/include/std/charconv
+++ b/libstdc++-v3/include/std/charconv
@@ -684,7 +684,7 @@ namespace __detail
     from_chars_result __res
       = __from_chars_float16_t(__first, __last, __val, __fmt);
     if (__res.ec == errc{})
-      __value = __val;
+      __value = _Float16(__val);
     return __res;
   }
 #endif
@@ -697,7 +697,7 @@ namespace __detail
     float __val;
     from_chars_result __res = from_chars(__first, __last, __val, __fmt);
     if (__res.ec == errc{})
-      __value = __val;
+      __value = _Float32(__val);
     return __res;
   }
 #endif
@@ -710,7 +710,7 @@ namespace __detail
     double __val;
     from_chars_result __res = from_chars(__first, __last, __val, __fmt);
     if (__res.ec == errc{})
-      __value = __val;
+      __value = _Float64(__val);
     return __res;
   }
 #endif
@@ -723,7 +723,7 @@ namespace __detail
     long double __val;
     from_chars_result __res = from_chars(__first, __last, __val, __fmt);
     if (__res.ec == errc{})
-      __value = __val;
+      __value = _Float128(__val);
     return __res;
   }
 #elif defined(__STDCPP_FLOAT128_T__) && defined(_GLIBCXX_HAVE_FLOAT128_MATH)
@@ -739,7 +739,7 @@ namespace __detail
     __extension__ __ieee128 __val;
     from_chars_result __res = from_chars(__first, __last, __val, __fmt);
     if (__res.ec == errc{})
-      __value = __val;
+      __value = _Float128(__val);
     return __res;
   }
 #else
@@ -760,7 +760,7 @@ namespace __detail
     from_chars_result __res
       = __from_chars_bfloat16_t(__first, __last, __val, __fmt);
     if (__res.ec == errc{})
-      __value = __val;
+      __value = __gnu_cxx::__bfloat16_t(__val);
     return __res;
   }
 #endif