The libgo implementation of math.Ldexp declared the libc "ldexp" as
taking an 'int' exponent argument, which is not quite right for 64-bit
platforms (exp arg is always int32); this could yield incorrect
results for exponent values outside the range of Minint32/Maxint32.
This patch by Than McIntosh fixes this by upating the type for the
libc version of ldexp, and adding guards to screen for out-of-range
exponents. This fixes https://golang.org/issue/21323. Bootstrapped
and ran Go tests on x86_64-pc-linux-gnu. Committed to mainline.
Ian
Index: gcc/go/gofrontend/MERGE
===================================================================
--- gcc/go/gofrontend/MERGE (revision 250873)
+++ gcc/go/gofrontend/MERGE (working copy)
@@ -1,4 +1,4 @@
-db685a1a9aa8b3b916dd6d1284895e01d73158e1
+5fd112e5c2968e94761c41519c451d789e23a92b
The first line of this file holds the git revision number of the last
merge done from the gofrontend repository.
Index: libgo/go/math/ldexp.go
===================================================================
--- libgo/go/math/ldexp.go (revision 250873)
+++ libgo/go/math/ldexp.go (working copy)
@@ -13,10 +13,15 @@ package math
// Ldexp(NaN, exp) = NaN
//extern ldexp
-func libc_ldexp(float64, int) float64
+func libc_ldexp(float64, int32) float64
func Ldexp(frac float64, exp int) float64 {
- r := libc_ldexp(frac, exp)
+ if exp > MaxInt32 {
+ exp = MaxInt32
+ } else if exp < MinInt32 {
+ exp = MinInt32
+ }
+ r := libc_ldexp(frac, int32(exp))
return r
}
