[9front] Re: ape modf infinite recursion

[Anthony Martin <ality@pbrane.org>]

Xiao-Yong Jin <meta.jxy@gmail.com> once said:
> modf(ip=0x7fffffffe9e8,d=0xffffffffffffffff)+0x43 /sys/src/ape/lib/ap/plan9/frexp.c:78
> modf(ip=0x7fffffffe9e8,d=0xffffffffffffffff)+0x43 /sys/src/ape/lib/ap/plan9/frexp.c:78
> modf(ip=0x7fffffffe9e8,d=0xffffffffffffffff)+0x43 /sys/src/ape/lib/ap/plan9/frexp.c:78

There was a fix to this on sources that was
apparently never picked up by 9front.

I've included it below but you can also find
it in David du Colombier's mirror:

https://github.com/0intro/plan9/commit/119c1d0c712512776162de1eca755006f07fe91c

Cheers,
  Anthony

diff --git a/sys/src/ape/lib/ap/plan9/frexp.c b/sys/src/ape/lib/ap/plan9/frexp.c
--- a/sys/src/ape/lib/ap/plan9/frexp.c
+++ b/sys/src/ape/lib/ap/plan9/frexp.c
@@ -73,6 +73,16 @@
 	Cheat x;
 	int e;

+	x.d = d;
+	e = (x.ms >> SHIFT) & MASK;
+	if(e == MASK){
+		*ip = d;
+		if(x.ls != 0 || (x.ms & 0xfffffL) != 0)	/* NaN */
+			return d;
+		/* ±Inf */
+		x.ms &= 0x80000000L;
+		return x.d;
+	}
 	if(d < 1) {
 		if(d < 0) {
 			f = modf(-d, ip);
@@ -82,8 +92,7 @@
 		*ip = 0;
 		return d;
 	}
-	x.d = d;
-	e = ((x.ms >> SHIFT) & MASK) - BIAS;
+	e -= BIAS;
 	if(e <= SHIFT+1) {
 		x.ms &= ~(0x1fffffL >> e);
 		x.ls = 0;