protect against long double type mismatches (mainly powerpc for now)
check in configure to be polite (failing early if we're going to fail)
and in vfprintf.c since that is the point at which a mismatching type
would be extremely dangerous.
diff --git a/configure b/configure
index 1d73472..48465f7 100755
--- a/configure
+++ b/configure
@@ -393,6 +393,27 @@
test "$SUBARCH" \
&& printf "configured for %s variant: %s\n" "$ARCH" "$ARCH$SUBARCH"
+#
+# Some archs (powerpc) have different possible long double formats
+# that the compiler can be configured for. The logic for whether this
+# is supported is in bits/float.h; in general, it is not. We need to
+# check for mismatches here or code in printf, strotd, and scanf will
+# be dangerously incorrect because it depends on (1) the macros being
+# correct, and (2) IEEE semantics.
+#
+printf "checking whether compiler's long double definition matches float.h... "
+echo '#include <float.h>' > "$tmpc"
+echo '#if LDBL_MANT_DIG == 53' >> "$tmpc"
+echo 'typedef char ldcheck[9-(int)sizeof(long double)];' >> "$tmpc"
+echo '#endif' >> "$tmpc"
+if $CC $CFLAGS_C99FSE -I./arch/$ARCH -I./include $CPPFLAGS $CFLAGS \
+ -c -o /dev/null "$tmpc" >/dev/null 2>&1 ; then
+printf "yes\n"
+else
+printf "no\n"
+fail "$0: error: unsupported long double type"
+fi
+
printf "creating config.mak... "
exec 3>&1 1>config.mak