cmd/compile: avoid converting huge floats to integers

Fixes #13471.

Change-Id: I232ad1729343d020254e313cfff182695ad6fc54
Reviewed-on: https://go-review.googlesource.com/17401
Reviewed-by: Russ Cox <rsc@golang.org>

diff --git a/src/cmd/compile/internal/gc/const.go b/src/cmd/compile/internal/gc/const.go
index bb42468713a45dc45cf4bb3ce9e1ca17fb06c5e6..0a00825b85617ba8fc8fa35070c79ce7dce1b2b2 100644 (file)
--- a/src/cmd/compile/internal/gc/const.go
+++ b/src/cmd/compile/internal/gc/const.go
@@ -379,8 +379,13 @@ func toint(v Val) Val {
 
        case CTFLT:
                i := new(Mpint)
-               if mpmovefltfix(i, v.U.(*Mpflt)) < 0 {
-                       Yyerror("constant %v truncated to integer", Fconv(v.U.(*Mpflt), obj.FmtSharp))
+               if f := v.U.(*Mpflt); mpmovefltfix(i, f) < 0 {
+                       msg := "constant %v truncated to integer"
+                       // provide better error message if mpmovefltfix failed because f was too large
+                       if f.Val.IsInt() {
+                               msg = "constant %v overflows integer"
+                       }
+                       Yyerror(msg, Fconv(f, obj.FmtSharp))
                }
                v.U = i
 

diff --git a/src/cmd/compile/internal/gc/mparith2.go b/src/cmd/compile/internal/gc/mparith2.go
index f70e342a961f64e6beb97124a48d5bb05986bbde..28c3a00825e9b4773065e44823fda7490889aa40 100644 (file)
--- a/src/cmd/compile/internal/gc/mparith2.go
+++ b/src/cmd/compile/internal/gc/mparith2.go
@@ -31,6 +31,12 @@ func mpmovefixfix(a, b *Mpint) {
 }
 
 func mpmovefltfix(a *Mpint, b *Mpflt) int {
+       // avoid converting huge floating-point numbers to integers
+       // (2*Mpprec is large enough to permit all tests to pass)
+       if b.Val.MantExp(nil) > 2*Mpprec {
+               return -1
+       }
+
        if _, acc := b.Val.Int(&a.Val); acc == big.Exact {
                return 0
        }

diff --git a/src/go/types/stdlib_test.go b/src/go/types/stdlib_test.go
index 8fc2ee145109feac53dbc1c8d6943b060551ebb4..6ff900424343384e3c1629d981e65c2d257132f4 100644 (file)
--- a/src/go/types/stdlib_test.go
+++ b/src/go/types/stdlib_test.go
@@ -151,6 +151,7 @@ func TestStdFixed(t *testing.T) {
                "issue11326.go",  // large constants
                "issue11326b.go", // large constants
                "issue11362.go",  // canonical import path check
+               "issue13471.go",  // large constants - remove once issue 11327 is fixed
        )
 }
 

diff --git a/test/fixedbugs/issue13471.go b/test/fixedbugs/issue13471.go
new file mode 100644 (file)
index 0000000..cda668a
--- /dev/null
+++ b/test/fixedbugs/issue13471.go
@@ -0,0 +1,25 @@
+// errorcheck
+
+// Copyright 2015 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Tests for golang.org/issue/13471
+
+package main
+
+func main() {
+       const _ int64 = 1e646456992 // ERROR "1.00000e\+646456992 overflows integer"
+       const _ int32 = 1e64645699  // ERROR "1.00000e\+64645699 overflows integer"
+       const _ int16 = 1e6464569   // ERROR "1.00000e\+6464569 overflows integer"
+       const _ int8 = 1e646456     // ERROR "1.00000e\+646456 overflows integer"
+       const _ int = 1e64645       // ERROR "1.00000e\+64645 overflows integer"
+
+       const _ uint64 = 1e646456992 // ERROR "1.00000e\+646456992 overflows integer"
+       const _ uint32 = 1e64645699  // ERROR "1.00000e\+64645699 overflows integer"
+       const _ uint16 = 1e6464569   // ERROR "1.00000e\+6464569 overflows integer"
+       const _ uint8 = 1e646456     // ERROR "1.00000e\+646456 overflows integer"
+       const _ uint = 1e64645       // ERROR "1.00000e\+64645 overflows integer"
+
+       const _ rune = 1e64645 // ERROR "1.00000e\+64645 overflows integer"
+}