[PATCH] libstdc++: Fix long double to_chars testcase [PR98384]

[Patrick Palka via Gcc-patches]

The testcase was failing to compile on some targets due to its use of
the non-standard functions nextupl and nextdownl.  This patch makes the
testcase instead use the C99 function nexttowardl in an equivalent
manner.

libstdc++-v3/ChangeLog:

        PR libstdc++/98384
        * testsuite/20_util/to_chars/long_double.cc: Use nexttowardl
        instead of the non-standard nextupl and nextdownl.
---
 .../testsuite/20_util/to_chars/long_double.cc | 25 +++++++++++++------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/libstdc++-v3/testsuite/20_util/to_chars/long_double.cc 
b/libstdc++-v3/testsuite/20_util/to_chars/long_double.cc
index 9d9ede7cf8a..4f72cb65400 100644
--- a/libstdc++-v3/testsuite/20_util/to_chars/long_double.cc
+++ b/libstdc++-v3/testsuite/20_util/to_chars/long_double.cc
@@ -32,6 +32,17 @@
 
 using namespace std;
 
+namespace detail
+{
+  long double
+  nextupl(long double x)
+  { return nexttowardl(x, numeric_limits<long double>::infinity()); }
+
+  long double
+  nextdownl(long double x)
+  { return nexttowardl(x, -numeric_limits<long double>::infinity()); }
+}
+
 // The long double overloads of std::to_chars currently just go through printf
 // (except for the hexadecimal formatting).
 
@@ -40,8 +51,8 @@ void
 test01()
 {
   const long double hex_testcases[]
-    = { nextdownl(numeric_limits<long double>::max()),
-       nextupl(numeric_limits<long double>::min()),
+    = { detail::nextdownl(numeric_limits<long double>::max()),
+       detail::nextupl(numeric_limits<long double>::min()),
        42.0L,
        0x1.2p+0L,
        0x1.23p+0L,
@@ -94,7 +105,7 @@ test01()
 
          {
            // Verify that the nearby values have a different shortest form.
-           testcase = nextdownl(testcase);
+           testcase = detail::nextdownl(testcase);
            result = to_chars(begin(to_chars_buffer), end(to_chars_buffer),
                              testcase, chars_format::hex);
            VERIFY( result.ec == errc{} );
@@ -103,7 +114,7 @@ test01()
            sprintf(printf_buffer, "%La", testcase);
            VERIFY( !strcmp(to_chars_buffer, printf_buffer+strlen("0x")) );
 
-           testcase = nextupl(nextupl(testcase));
+           testcase = detail::nextupl(detail::nextupl(testcase));
            result = to_chars(begin(to_chars_buffer), end(to_chars_buffer),
                              testcase, chars_format::hex);
            VERIFY( result.ec == errc{} );
@@ -112,7 +123,7 @@ test01()
            sprintf(printf_buffer, "%La", testcase);
            VERIFY( !strcmp(to_chars_buffer, printf_buffer+strlen("0x")) );
 
-           testcase = nextdownl(testcase);
+           testcase = detail::nextdownl(testcase);
          }
 
        for (int precision = -1; precision < 50; precision++)
@@ -173,7 +184,7 @@ test02()
          *result.ptr = '\0';
          char nearby_buffer[50000];
            {
-             const long double smaller = nextdownl(value);
+             const long double smaller = detail::nextdownl(value);
              result = to_chars(begin(nearby_buffer), end(nearby_buffer),
                                smaller, fmt);
              VERIFY( result.ec == errc{} );
@@ -182,7 +193,7 @@ test02()
            }
 
            {
-             long double larger = nextupl(value);
+             long double larger = detail::nextupl(value);
              result = to_chars(begin(nearby_buffer), end(nearby_buffer),
                                larger, fmt);
              VERIFY( result.ec == errc{} );
-- 
2.30.0