Fix float64 to uint{8,16,32} conversion.
Before this change, GopherJS compiler emitted `(f >> 0)` expression to
convert a float64 `f` to any non-64-bit unsigned integer type. This is
incorrect, because `>>` is a signed bitshift operator in JS, so the
returned value remained signed. Moreover, it did not take into account
to bit size of the target type.
By removing the switch cause, we make the compiler fall through to the
default clause where `fc.fixNumber()` actually does the right thing,
taking the target into account.
Fixes #733.
diff --git a/compiler/expressions.go b/compiler/expressions.go
index 2768e3d..11b2840 100644
--- a/compiler/expressions.go
+++ b/compiler/expressions.go
@@ -1128,8 +1128,6 @@
return fc.fixNumber(fc.formatParenExpr("%1l + ((%1h >> 31) * 4294967296)", expr), t)
}
return fc.fixNumber(fc.formatExpr("%s.$low", fc.translateExpr(expr)), t)
- case isFloat(basicExprType):
- return fc.formatParenExpr("%e >> 0", expr)
case types.Identical(exprType, types.Typ[types.UnsafePointer]):
return fc.translateExpr(expr)
default:
diff --git a/tests/numeric_test.go b/tests/numeric_test.go
index df06db5..4eaa678 100644
--- a/tests/numeric_test.go
+++ b/tests/numeric_test.go
@@ -5,6 +5,8 @@
"runtime"
"testing"
"testing/quick"
+
+ "github.com/gopherjs/gopherjs/js"
)
// naiveMul64 performs 64-bit multiplication without using the multiplication
@@ -93,3 +95,26 @@
}
})
}
+
+func TestIssue733(t *testing.T) {
+ if runtime.GOOS != "js" {
+ t.Skip("test uses GopherJS-specific features")
+ }
+
+ t.Run("sign", func(t *testing.T) {
+ f := float64(-1)
+ i := uint32(f)
+ underlying := js.InternalObject(i).Float() // Get the raw JS number behind i.
+ if want := float64(4294967295); underlying != want {
+ t.Errorf("Got: uint32(float64(%v)) = %v. Want: %v.", f, underlying, want)
+ }
+ })
+ t.Run("truncation", func(t *testing.T) {
+ f := float64(300)
+ i := uint8(f)
+ underlying := js.InternalObject(i).Float() // Get the raw JS number behind i.
+ if want := float64(44); underlying != want {
+ t.Errorf("Got: uint32(float64(%v)) = %v. Want: %v.", f, underlying, want)
+ }
+ })
+}
