libstdc++: Fix std::numeric_limits<__float128>::max_digits10 [PR121374]

When I added this explicit specialization in r14-1433-gf150a084e25eaa I
used the wrong value for the number of mantissa digits (I used 112
instead of 113). Then when I refactored it in r14-1582-g6261d10521f9fd I
used the value calculated from the incorrect value (35 instead of 36).

libstdc++-v3/ChangeLog:

	PR libstdc++/121374
	* include/std/limits (numeric_limits<__float128>::max_digits10):
	Fix value.
	* testsuite/18_support/numeric_limits/128bit.cc: Check value.

(cherry picked from commit cf88ed5bf20c86ca38da19358ff79a34adb4d0b5)

diff --git a/libstdc++-v3/include/std/limits b/libstdc++-v3/include/std/limits
index 2331c25599a0ca2ecb8dbec49bbcb3c8e85a417c..5662a22e9275d1a09aea91bd35ffee5b8e87657d 100644 (file)
--- a/libstdc++-v3/include/std/limits
+++ b/libstdc++-v3/include/std/limits
@@ -2129,7 +2129,7 @@ __glibcxx_float_n(128)
       static _GLIBCXX_USE_CONSTEXPR int digits = 113;
       static _GLIBCXX_USE_CONSTEXPR int digits10 = 33;
 #if __cplusplus >= 201103L
-      static constexpr int max_digits10 = 35;
+      static constexpr int max_digits10 = 36;
 #endif
       static _GLIBCXX_USE_CONSTEXPR bool is_signed = true;
       static _GLIBCXX_USE_CONSTEXPR bool is_integer = false;

diff --git a/libstdc++-v3/testsuite/18_support/numeric_limits/128bit.cc b/libstdc++-v3/testsuite/18_support/numeric_limits/128bit.cc
index b13d83776ba39fa38f511fd832dca16336c9de8b..bf12b65f91a5e19d1658ab22478c1e94919cf65e 100644 (file)
--- a/libstdc++-v3/testsuite/18_support/numeric_limits/128bit.cc
+++ b/libstdc++-v3/testsuite/18_support/numeric_limits/128bit.cc
@@ -4,6 +4,11 @@
 
 #if __SIZEOF_FLOAT128__
 __extension__ template class std::numeric_limits<__float128>;
+
+# if __cplusplus >= 201103L
+static_assert( std::numeric_limits<__float128>::max_digits10 == 36,
+              "PR libstdc++/121374" );
+# endif
 #endif
 
 #if __SIZEOF_INT128__