gencffi: Detect functions returning a Go error

_examples/pyerrors/pyerrors.go

@@ -0,0 +1,16 @@
+// Copyright 2017 The go-python Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package pyerrors holds functions returning an error.
+package pyerrors
+
+import "errors"
+
+// Div is a function for detecting errors.
+func Div(i, j int) (int, error) {
+	if j == 0 {
+		return 0, errors.New("Divide by zero.")
+	}
+	return i / j, nil
+}

_examples/pyerrors/test.py

@@ -0,0 +1,18 @@
+# Copyright 2017 The go-python Authors.  All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+## py2/py3 compat
+from __future__ import print_function
+
+import pyerrors
+
+def div(a, b):
+    try:
+        r = pyerrors.Div(a, b)
+        print("pyerrors.Div(%d, %d) = %d"% (a, b, r))
+    except Exception as e:
+        print(str(e))
+
+div(5,0)
+div(5,2)

bind/gencffi.go

@@ -42,6 +42,7 @@ typedef struct { void *data; GoInt len; GoInt cap; } GoSlice;
 
 extern GoString _cgopy_GoString(char* p0);
 extern char* _cgopy_CString(GoString p0);
+extern void _cgopy_FreeCString(char* p0);
 extern GoUint8 _cgopy_ErrorIsNil(GoInterface p0);
 extern char* _cgopy_ErrorString(GoInterface p0);
 extern void cgopy_incref(void* p0);
@@ -81,7 +82,9 @@ class _cffi_helper(object):
     @staticmethod
     def cffi_cgopy_cnv_c2py_string(c):
         s = _cffi_helper.lib._cgopy_CString(c)
-        return ffi.string(s)
+        pystr = ffi.string(s)
+        _cffi_helper.lib._cgopy_FreeCString(s)
+        return pystr
 
     @staticmethod
     def cffi_cgopy_cnv_c2py_int(c):
@@ -98,6 +101,7 @@ class _cffi_helper(object):
     @staticmethod
     def cffi_cgopy_cnv_c2py_uint(c):
         return int(c)
+
 # make sure Cgo is loaded and initialized
 _cffi_helper.lib.cgo_pkg_%[1]s_init()
 `

bind/gencffi_cdef.go

@@ -32,25 +32,31 @@ func (g *cffiGen) genCdefType(sym *symbol) {
 
 func (g *cffiGen) genCdefFunc(f Func) {
 	var params []string
+	var retParams []string
 	var cdef_ret string
 	sig := f.sig
 	rets := sig.Results()
+	args := sig.Params()
 
 	switch len(rets) {
 	case 0:
 		cdef_ret = "void"
 	case 1:
 		cdef_ret = rets[0].sym.cgoname
 	default:
-		cdef_ret = "cgo_func_" + f.name + "_return"
+		for i := 0; i < len(rets); i++ {
+			retParam := rets[i].sym.cgoname + " r" + strconv.Itoa(i)
+			retParams = append(retParams, retParam)
+		}
+		cdef_ret = "cgo_func_" + f.id + "_return"
+		retParamStrings := strings.Join(retParams, "; ")
+		g.wrapper.Printf("typedef struct { %[1]s; } %[2]s;\n", retParamStrings, cdef_ret)
 	}
 
-	args := sig.Params()
 	for i := 0; i < len(args); i++ {
 		paramVar := args[i].sym.cgoname + " " + "p" + strconv.Itoa(i)
 		params = append(params, paramVar)
 	}
-
 	paramString := strings.Join(params, ", ")
 	g.wrapper.Printf("extern %[1]s cgo_func_%[2]s(%[3]s);\n", cdef_ret, f.id, paramString)
 }

bind/gencffi_func.go

@@ -109,6 +109,38 @@ func (g *cffiGen) genFuncBody(f Func) {
 
 	g.wrapper.Printf("_cffi_helper.lib.cgo_func_%[1]s(%[2]s)\n", f.id, strings.Join(funcArgs, ", "))
 
+	if f.err {
+		switch nres {
+		case 1:
+			g.wrapper.Printf("if not _cffi_helper.lib._cgopy_ErrorIsNil(cret):\n")
+			g.wrapper.Indent()
+			g.wrapper.Printf("c_err_str = _cffi_helper.lib._cgopy_ErrorString(cret)\n")
+			g.wrapper.Printf("py_err_str = ffi.string(c_err_str)\n")
+			g.wrapper.Printf("_cffi_helper.lib._cgopy_FreeCString(c_err_str)\n")
+			g.wrapper.Printf("raise RuntimeError(py_err_str)\n")
+			g.wrapper.Outdent()
+			g.wrapper.Printf("return\n")
+			return
+		case 2:
+			g.wrapper.Printf("if not _cffi_helper.lib._cgopy_ErrorIsNil(cret.r1):\n")
+			g.wrapper.Indent()
+			g.wrapper.Printf("c_err_str = _cffi_helper.lib._cgopy_ErrorString(cret.r1)\n")
+			g.wrapper.Printf("py_err_str = ffi.string(c_err_str)\n")
+			g.wrapper.Printf("_cffi_helper.lib._cgopy_FreeCString(c_err_str)\n")
+			g.wrapper.Printf("raise RuntimeError(py_err_str)\n")
+			g.wrapper.Outdent()
+			if res[0].sym.hasConverter() {
+				g.wrapper.Printf("r0 = _cffi_helper.cffi_%[1]s(cret.r0)\n", res[0].sym.c2py)
+				g.wrapper.Printf("return r0\n")
+			} else {
+				g.wrapper.Printf("return cret.r0\n")
+			}
+			return
+		default:
+			panic(fmt.Errorf("bind: function/method with more than 2 results not supported! (%s)", f.ID()))
+		}
+	}
+
 	switch nres {
 	case 0:
 		// no-op

bind/gengo.go

@@ -89,6 +89,11 @@ func _cgopy_ErrorString(err error) *C.char {
 	return C.CString(err.Error())
 }
 
+//export _cgopy_FreeCString
+func _cgopy_FreeCString(cs *C.char) {
+	C.free(unsafe.Pointer(cs))
+}
+
 // --- end cgo helpers ---
 
 // --- begin cref helpers ---

main_test.go

@@ -667,3 +667,20 @@ doc(pkg):
 `),
 	})
 }
+
+func TestPyErrors(t *testing.T) {
+	t.Parallel()
+	testPkg(t, pkg{
+		path: "_examples/pyerrors",
+		want: []byte(`Divide by zero.
+pyerrors.Div(5, 2) = 2
+`),
+	})
+
+	testPkgWithCFFI(t, pkg{
+		path: "_examples/pyerrors",
+		want: []byte(`Divide by zero.
+pyerrors.Div(5, 2) = 2
+`),
+	})
+}