src/cmd/cgo/gcc.go  |  2 +-
 src/cmd/cgo/main.go |  3 ++-
 src/cmd/cgo/out.go  | 17 ++++++++++-------
 src/cmd/cgo/util.go |  2 +-

diff --git a/src/cmd/cgo/gcc.go b/src/cmd/cgo/gcc.go
index e4e56d8dd6614d06f91b010c64569510bd072a5d..e7e99bc56b689e7d21ad7e361d8309e41c539311 100644
--- a/src/cmd/cgo/gcc.go
+++ b/src/cmd/cgo/gcc.go
@@ -697,7 +697,7 @@ 	}
 	return nil
 }
 
-const gccTmp = "_obj/_cgo_.o"
+var gccTmp = objDir + "_cgo_.o"
 
 // gccCmd returns the gcc command line to use for compiling
 // the input.
diff --git a/src/cmd/cgo/main.go b/src/cmd/cgo/main.go
index 84aeccc2178ac6e4b1bf626a2a7fecbd5f2c1a84..be9c2bc4fbdbd45eddb3488c3dd72e19b6c2c583 100644
--- a/src/cmd/cgo/main.go
+++ b/src/cmd/cgo/main.go
@@ -18,6 +18,7 @@ 	"go/ast"
 	"go/token"
 	"io"
 	"os"
+	"path/filepath"
 	"reflect"
 	"strings"
 )
@@ -228,7 +229,7 @@ 			os.Exit(2)
 		}
 		pkg := f.Package
 		if dir := os.Getenv("CGOPKGPATH"); dir != "" {
-			pkg = dir + "/" + pkg
+			pkg = filepath.Join(dir, pkg)
 		}
 		p.PackagePath = pkg
 		p.writeOutput(f, input)
diff --git a/src/cmd/cgo/out.go b/src/cmd/cgo/out.go
index dbc7bcf695520b0f3ec6a905a98007e63730698d..7eecb3437fc8ed6ad3c32a66944a237f18888d93 100644
--- a/src/cmd/cgo/out.go
+++ b/src/cmd/cgo/out.go
@@ -14,17 +14,20 @@ 	"go/ast"
 	"go/printer"
 	"go/token"
 	"os"
+	"path/filepath"
 	"strings"
 )
+
+var objDir = "_obj" + string(filepath.Separator)
 
 // writeDefs creates output files to be compiled by 6g, 6c, and gcc.
 // (The comments here say 6g and 6c but the code applies to the 8 and 5 tools too.)
 func (p *Package) writeDefs() {
-	fgo2 := creat("_obj/_cgo_gotypes.go")
-	fc := creat("_obj/_cgo_defun.c")
-	fm := creat("_obj/_cgo_main.c")
+	fgo2 := creat(objDir + "_cgo_gotypes.go")
+	fc := creat(objDir + "_cgo_defun.c")
+	fm := creat(objDir + "_cgo_main.c")
 
-	fflg := creat("_obj/_cgo_flags")
+	fflg := creat(objDir + "_cgo_flags")
 	for k, v := range p.CgoFlags {
 		fmt.Fprintf(fflg, "_CGO_%s=%s\n", k, v)
 	}
@@ -285,8 +288,8 @@ 	if strings.HasSuffix(base, ".go") {
 		base = base[0 : len(base)-3]
 	}
 	base = strings.Map(slashToUnderscore, base)
-	fgo1 := creat("_obj/" + base + ".cgo1.go")
-	fgcc := creat("_obj/" + base + ".cgo2.c")
+	fgo1 := creat(objDir + base + ".cgo1.go")
+	fgcc := creat(objDir + base + ".cgo2.c")
 
 	p.GoFiles = append(p.GoFiles, base+".cgo1.go")
 	p.GccFiles = append(p.GccFiles, base+".cgo2.c")
@@ -361,7 +364,7 @@
 // Write out the various stubs we need to support functions exported
 // from Go so that they are callable from C.
 func (p *Package) writeExports(fgo2, fc, fm *os.File) {
-	fgcc := creat("_obj/_cgo_export.c")
+	fgcc := creat(objDir + "_cgo_export.c")
 	fgcch := creat("_cgo_export.h")
 
 	fmt.Fprintf(fgcch, "/* Created by cgo - DO NOT EDIT. */\n")
diff --git a/src/cmd/cgo/util.go b/src/cmd/cgo/util.go
index 1ca24103e30d2340bfb01b37f40293783c22ea8a..e79b0e1bfae55fd1685309dd32ddc1d0eb6542f5 100644
--- a/src/cmd/cgo/util.go
+++ b/src/cmd/cgo/util.go
@@ -103,7 +103,7 @@ 	return f
 }
 
 func slashToUnderscore(c int) int {
-	if c == '/' {
+	if c == '/' || c == '\\' || c == ':' {
 		c = '_'
 	}
 	return c