+#
+# 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>' > "$tmpc"
+echo '#define C(m,s) (m==LDBL_MANT_DIG && s==sizeof(long double))' >> "$tmpc"
+echo 'typedef char ldcheck[(C(53,8)||C(64,12)||C(64,16)||C(113,16))*2-1];' >> "$tmpc"
+if $CC $CFLAGS_C99FSE \
+ -I$srcdir/arch/$ARCH -I$srcdir/arch/generic -I$srcdir/include \
+ $CPPFLAGS $CFLAGS -c -o /dev/null "$tmpc" >/dev/null 2>&1 ; then
+printf "yes\n"
+else
+printf "no\n"
+fail "$0: error: unsupported long double type"
+fi
+
+#
+# Some build systems globally pass in broken CFLAGS like -ffast-math
+# for all packages. On recent GCC we can detect this and error out
+# early rather than producing a seriously-broken math library.
+#
+if trycppif "__FAST_MATH__" \
+ "$CFLAGS_C99FSE $CPPFLAGS $CFLAGS" ; then
+fail "$0: error: compiler has broken floating point; check CFLAGS"
+fi
+