warn the user that NetBSD's long double support isn't very good

1 files changed, 35 insertions, 0 deletions

diff --git a/hints/netbsd.sh b/hints/netbsd.sh
index 445680d8ba..5c9f5bcbd5 100644
--- a/hints/netbsd.sh
+++ b/hints/netbsd.sh
@@ -265,3 +265,38 @@ case "$osver" in
         d_fchmodat="$undef"
         ;;
 esac
+
+cat >UU/uselongdouble.cbu <<'EOCBU'
+# This script UU/uselongdouble.cbu will get 'called-back' by Configure
+# after it has prompted the user for whether to use long doubles.
+#
+# See https://github.com/Perl/perl5/issues/17853 and https://github.com/Perl/perl5/issues/17854
+case "$uselongdouble" in
+$define|true|[yY]*)
+    cat >try.c <<\TRY
+#include <stdio.h>
+#include <math.h>
+
+long double x = 1.0;
+
+int main(int argc, char **argv) {
+    double e1 = exp(1.0);
+    /* as of NetBSD 9.0 expl() just calls exp(),
+       Fail here if they're equal. */
+    return expl(x) == (long double)e1;
+}
+TRY
+    if $cc -o try $ccflags $ldflags try.c -lm && $run ./try; then
+        echo "NetBSD seem to have fixed expl (and hopefully more)" >&4
+    else
+        cat <<EOM >&4
+
+Warning! NetBSD's long double support is limited enough that it will cause
+test failures, and possibly build failures, and this doesn't appear to have
+been fixed in the release you're running.
+
+EOM
+    fi
+;;
+esac
+EOCBU