Merge branch 'master' of github.com:chai2010/advanced-go-programming-book

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,4 @@
+## Expected Behavior
+
+## Actual Behavior
+

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,14 @@
+## Description
+
+A few sentences describing the overall goals of the pull request's commits.
+
+## Designs
+
+If it's a feature, please write your code designs here.
+
+## Notes to reviewers
+
+Review the following things, including but not limit to:
+
+1. Design
+2. Code (styles, magic...)

.gitignore

@@ -23,3 +23,9 @@ _obj
 
 # macOS
 .DS_Store
+
+*.so
+*.dll
+*.obj
+*.o
+a.out

SUMMARY.md

@@ -15,12 +15,16 @@
    * [2.3. CGO编程基础](ch2-cgo/ch2-03-basic.md)
    * [2.4. CGO内存模型](ch2-cgo/ch2-04-memory.md)
    * [2.5. C++类包装](ch2-cgo/ch2-05-class.md)
-   * [2.6. 命令行工具和构建参数(TODO)](ch2-cgo/ch2-06-build.md)
-   * [2.7. 静态库和动态库(TODO)](ch2-cgo/ch2-07-dll.md)
-   * [2.8. 例子: 封装LevelDB(TODO)](ch2-cgo/ch2-08-leveldb.md)
+   * [2.6. CGO包的可移植性(TODO)](ch2-cgo/ch2-06-go-get-friendly.md)
+   * [2.7. Go实现Python模块(TODO)](ch2-cgo/ch2-07-py-module.md)
+   * [2.8. SWIG(TODO)](ch2-cgo/ch2-08-swig.md)
    * [2.9. 补充说明(TODO)](ch2-cgo/ch2-09-faq.md)
+* [第三章 Go汇编语言](ch3-asm/readme.md)
+* [第四章 Go和脚本语言](ch4-xlang/readme.md)
 * [第六章 Go和Web](ch6-web/readme.md)
    * [6.1. Web开发简介](ch6-web/ch6-01-introduction.md)
+   * [6.2. Router请求路由](ch6-web/ch6-02-router.md)
+   * [6.3. Middleware中间件](ch6-web/ch6-03-middleware.md)
 * [附录](appendix/readme.md)
    * [附录A: Go语言常见坑](appendix/appendix-a-trap.md)
    * [附录B: 参考资料](appendix/appendix-b-ref.md)

ch1-basic/ch1-05-mem.md

@@ -61,17 +61,21 @@ import (
 	"sync/atomic"
 )
 
-var total int64
+var total uint64
 
 func worker(wg *sync.WaitGroup) {
 	defer wg.Done()
 
-	for i := 0; i <= 100; i++ {
+	var i uint64
+	for i = 0; i <= 100; i++ {
 		atomic.AddUint64(&total, i)
 	}
 }
 
 func main() {
+	var wg sync.WaitGroup
+	wg.Add(2)
+
 	go worker(&wg)
 	go worker(&wg)
 	wg.Wait()

ch2-cgo/ch2-02-cgo-types.md

@@ -59,6 +59,39 @@ uint64_t | C.uint64_t | uint64
 
 前文说过，如果C语言的类型是由多个关键字组成，无法通过虚拟的“C”包直接访问。比如C语言的`unsigned short`不能直接通过`C.unsigned short`访问。但是，在`<stdint.h>`中通过使用C语言的`typedef`关键字将`unsigned short`重新定义为`uint16_t`一个单词的类型后，我们就可以通过`C.uint16_t`访问原来的`unsigned short`类型了。对于比较复杂的C语言类型，推荐使用`typedef`关键字提高一个规则的类型命名，这样更利于在CGO中访问。
 
+## Go 字符串和切片
+
+在CGO生成的`_cgo_export.h`头文件中还会为Go语言特有的字符串、切片、字典、接口和管道等特有的数据类型生成对应的C语言类型：
+
+```c
+typedef struct { const char *p; GoInt n; } GoString;
+typedef void *GoMap;
+typedef void *GoChan;
+typedef struct { void *t; void *v; } GoInterface;
+typedef struct { void *data; GoInt len; GoInt cap; } GoSlice;
+```
+
+不过需要注意的是，其中只有Go语言的字符串和切片在CGO中有一定的使用价值，因为字符串和切片可以在Go调用C语言函数时马上使用。而其它的类型在C语言环境并无使用的价值，因为CGO并未针对这些类型提供相关的辅助函数，而且因为Go语言特有的内存模型的原因导致我们无法保持这些由Go语言管理的内存指针。
+
+在导出的C语言函数中我们可以直接使用Go字符串和切片。假设有以下两个导出函数：
+
+```go
+//export helloString
+func helloString(s string) {}
+
+//export helloSlice
+func helloSlice(s []byte) {}
+```
+
+CGO生成的`_cgo_export.h`头文件会包含以下的函数声明：
+
+```c
+extern void helloString(GoString p0);
+extern void helloSlice(GoSlice p0);
+```
+
+不过需要注意的是，如果使用了GoString类型会对`_cgo_export.h`头文件产生依赖，而这个头文件是动态输出的。更严谨的做法是为C语言函数接口定义严格的头文件，然后基于稳定的头文件实现代码。
+
 ## 结构体、联合、枚举类型
 
 C语言的结构体、联合、枚举类型不能作为匿名成员被嵌入到Go语言的结构体中。在Go语言中，我们可以通过`C.struct_xxx`来访问C语言中定义的`struct xxx`结构体类型。结构体的内存布局按照C语言的通用对齐规则，在32位Go语言环境C语言结构体也按照32位对齐规则，在64位Go语言环境按照64位的对齐规则。对于指定了特殊对齐规则的结构体，无法在CGO中访问。

ch2-cgo/ch2-06-build.md

@@ -1,3 +0,0 @@
-# 2.6. 命令行工具和构建参数(TODO)
-
-TODO

ch2-cgo/ch2-06-go-get-friendly.md

@@ -0,0 +1,19 @@
+# 2.6. CGO包的可移植性(TODO)
+
+TODO
+
+<!--
+可移植的cgo
+
+小的cgo包直接内置c/c++代码
+
+1. copy到本目录
+
+2. 创建 include 文件
+
+很大的c包，全部内置会导致构建复杂化
+
+分2步，1 go generate 进行构建
+2 lib 包含
+
+-->

ch2-cgo/ch2-07-dll.md

@@ -1,4 +0,0 @@
-# 2.7 静态库和动态库(TODO)
-
-TODO
-

ch2-cgo/ch2-07-py-module.md

@@ -0,0 +1,9 @@
+# 2.7 Go实现Python模块(TODO)
+
+TODO
+
+<!--
+静态库和动态库
+
+实战: py 模块
+-->

ch2-cgo/ch2-08-leveldb.md

@@ -1,3 +0,0 @@
-# 2.8. 封装LevelDB(TODO)
-
-TODO

ch2-cgo/ch2-08-swig.md

@@ -0,0 +1,7 @@
+# 2.8. SWIG(TODO)
+
+TODO
+
+<!--
+swig 简单说明
+-->

ch2-cgo/ch2-09-faq.md

@@ -1,3 +1,11 @@
 # 2.9. 补充说明(TODO)
 
 TODO
+
+<!--
+cgo的风险和不足
+
+不要用c模拟Go字符串
+不要试图越过Go运行时的边界
+有些事情是不可为的，比如 bsearch 类似接口完全没有继承的价值（代价太高）
+-->

ch3-asm/readme.md

@@ -0,0 +1,3 @@
+# 第三章 Go汇编语言
+
+TODO

ch4-xlang/readme.md

@@ -0,0 +1,3 @@
+# 第四章 Go和脚本语言
+
+TODO

examples/ch2-07/hello-py/Makefile

@@ -0,0 +1,12 @@
+default:
+	go build -buildmode=c-shared -o gopkg.so main.go
+	python3 -c 'import gopkg; print(gopkg.system("time"))'
+	python3 -c 'import gopkg; print(gopkg.sum(2, 3))'
+
+clean:
+	-rm *.so
+
+# PKG_CONFIG=python3-config go build -buildmode=c-shared -o say-hello.so main.go
+# python3-config --ldflags
+# python3-config --include
+

examples/ch2-07/hello-py/gopkg.h

@@ -0,0 +1,106 @@
+/* Created by "go tool cgo" - DO NOT EDIT. */
+
+/* package command-line-arguments */
+
+/* Start of preamble from import "C" comments.  */
+
+
+#line 3 "/Users/chai/go/src/github.com/chai2010/advanced-go-programming-book/examples/ch2-07/hello-py/main.go"
+
+// macOS:
+// python3-config --cflags
+// python3-config --ldflags
+
+
+
+// linux
+
+
+// windows
+// should generate libpython3.a from python3.lib
+
+#define Py_LIMITED_API
+#include <Python.h>
+
+static PyObject *
+spam_system(PyObject *self, PyObject *args) {
+	const char *command;
+	if (!PyArg_ParseTuple(args, "s", &command)) {
+		return NULL;
+	}
+
+	int status = system(command);
+	return PyLong_FromLong(status);
+}
+
+extern PyObject *sum(PyObject *self, PyObject *args);
+
+static PyMethodDef modMethods[] = {
+	{"system",  spam_system, METH_VARARGS, "Execute a shell command."},
+	{"sum",  sum, METH_VARARGS, "Execute a shell command."},
+	{NULL, NULL, 0, NULL}
+};
+
+static PyObject* PyInit_gopkg_(void) {
+	static struct PyModuleDef module = {
+		PyModuleDef_HEAD_INIT, "gopkg", NULL, -1, modMethods,
+	};
+	return (void*)PyModule_Create(&module);
+}
+
+#line 1 "cgo-generated-wrapper"
+
+
+/* End of preamble from import "C" comments.  */
+
+
+/* Start of boilerplate cgo prologue.  */
+#line 1 "cgo-gcc-export-header-prolog"
+
+#ifndef GO_CGO_PROLOGUE_H
+#define GO_CGO_PROLOGUE_H
+
+typedef signed char GoInt8;
+typedef unsigned char GoUint8;
+typedef short GoInt16;
+typedef unsigned short GoUint16;
+typedef int GoInt32;
+typedef unsigned int GoUint32;
+typedef long long GoInt64;
+typedef unsigned long long GoUint64;
+typedef GoInt64 GoInt;
+typedef GoUint64 GoUint;
+typedef __SIZE_TYPE__ GoUintptr;
+typedef float GoFloat32;
+typedef double GoFloat64;
+typedef float _Complex GoComplex64;
+typedef double _Complex GoComplex128;
+
+/*
+  static assertion to make sure the file is being used on architecture
+  at least with matching size of GoInt.
+*/
+typedef char _check_for_64_bit_pointer_matching_GoInt[sizeof(void*)==64/8 ? 1:-1];
+
+typedef struct { const char *p; GoInt n; } GoString;
+typedef void *GoMap;
+typedef void *GoChan;
+typedef struct { void *t; void *v; } GoInterface;
+typedef struct { void *data; GoInt len; GoInt cap; } GoSlice;
+
+#endif
+
+/* End of boilerplate cgo prologue.  */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+extern PyObject* sum(PyObject* p0, PyObject* p1);
+
+extern PyObject* PyInit_gopkg();
+
+#ifdef __cplusplus
+}
+#endif

examples/ch2-07/hello-py/main.go

@@ -0,0 +1,66 @@
+package main
+
+/*
+// macOS:
+// python3-config --cflags
+// python3-config --ldflags
+#cgo darwin CFLAGS: -I/Library/Frameworks/Python.framework/Versions/3.6/include/python3.6m -I/Library/Frameworks/Python.framework/Versions/3.6/include/python3.6m -fno-strict-aliasing -Wsign-compare -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes  -g
+#cgo darwin LDFLAGS: -L/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/config-3.6m-darwin -lpython3.6m -ldl -framework CoreFoundation
+
+// linux
+#cgo linux pkg-config: python3
+
+// windows
+// should generate libpython3.a from python3.lib
+
+#define Py_LIMITED_API
+#include <Python.h>
+
+static PyObject *
+spam_system(PyObject *self, PyObject *args) {
+	const char *command;
+	if (!PyArg_ParseTuple(args, "s", &command)) {
+		return NULL;
+	}
+
+	int status = system(command);
+	return PyLong_FromLong(status);
+}
+
+extern PyObject *sum(PyObject *self, PyObject *args);
+
+static PyMethodDef modMethods[] = {
+	{"system",  spam_system, METH_VARARGS, "Execute a shell command."},
+	{"sum",  sum, METH_VARARGS, "Execute a shell command."},
+	{NULL, NULL, 0, NULL}
+};
+
+static PyObject* PyInit_gopkg_(void) {
+	static struct PyModuleDef module = {
+		PyModuleDef_HEAD_INIT, "gopkg", NULL, -1, modMethods,
+	};
+	return (void*)PyModule_Create(&module);
+}
+*/
+import "C"
+
+import (
+	"fmt"
+)
+
+func main() {}
+
+//  export SayHello
+func SayHello(name *C.char) {
+	fmt.Printf("hello %s!\n", C.GoString(name))
+}
+
+//export sum
+func sum(self, args *C.PyObject) *C.PyObject {
+	return C.PyLong_FromLongLong(9527) // TODO
+}
+
+//export PyInit_gopkg
+func PyInit_gopkg() *C.PyObject {
+	return C.PyInit_gopkg_()
+}

examples/ch2-07/hello-so/Makefile

@@ -0,0 +1,11 @@
+default:
+	go build -buildmode=c-shared -o say-hello.so main.go
+	gcc -Wall _test_so.c ./say-hello.so
+	./a.out
+
+run-py3:
+	python3 hello.py
+
+clean:
+	-rm *.so
+	-rm *.out

examples/ch2-07/hello-so/_test_so.c

@@ -0,0 +1,7 @@
+#include "say-hello.h"
+#include <stdio.h>
+
+int main() {
+	SayHello("gopher");
+	return 0;
+}

examples/ch2-07/hello-so/hello.py

@@ -0,0 +1,9 @@
+from ctypes import *
+
+libso = CDLL("./say-hello.so")
+
+SayHello = libso.SayHello
+SayHello.argtypes = [c_char_p]
+SayHello.restype = None
+
+SayHello(c_char_p(b"hello"))

examples/ch2-07/hello-so/main.go

@@ -0,0 +1,11 @@
+package main
+
+import "C"
+import "fmt"
+
+func main() {}
+
+//export SayHello
+func SayHello(name *C.char) {
+	fmt.Printf("hello %s!\n", C.GoString(name))
+}

examples/ch2-07/hello-so/say-hello.h

@@ -0,0 +1,60 @@
+/* Created by "go tool cgo" - DO NOT EDIT. */
+
+/* package command-line-arguments */
+
+/* Start of preamble from import "C" comments.  */
+
+
+
+
+/* End of preamble from import "C" comments.  */
+
+
+/* Start of boilerplate cgo prologue.  */
+#line 1 "cgo-gcc-export-header-prolog"
+
+#ifndef GO_CGO_PROLOGUE_H
+#define GO_CGO_PROLOGUE_H
+
+typedef signed char GoInt8;
+typedef unsigned char GoUint8;
+typedef short GoInt16;
+typedef unsigned short GoUint16;
+typedef int GoInt32;
+typedef unsigned int GoUint32;
+typedef long long GoInt64;
+typedef unsigned long long GoUint64;
+typedef GoInt64 GoInt;
+typedef GoUint64 GoUint;
+typedef __SIZE_TYPE__ GoUintptr;
+typedef float GoFloat32;
+typedef double GoFloat64;
+typedef float _Complex GoComplex64;
+typedef double _Complex GoComplex128;
+
+/*
+  static assertion to make sure the file is being used on architecture
+  at least with matching size of GoInt.
+*/
+typedef char _check_for_64_bit_pointer_matching_GoInt[sizeof(void*)==64/8 ? 1:-1];
+
+typedef struct { const char *p; GoInt n; } GoString;
+typedef void *GoMap;
+typedef void *GoChan;
+typedef struct { void *t; void *v; } GoInterface;
+typedef struct { void *data; GoInt len; GoInt cap; } GoSlice;
+
+#endif
+
+/* End of boilerplate cgo prologue.  */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+extern void SayHello(char* p0);
+
+#ifdef __cplusplus
+}
+#endif

examples/ch2-xx/hello/.gitignore

@@ -0,0 +1 @@
+!/_obj

examples/ch2-xx/hello/Makefile

@@ -0,0 +1,2 @@
+default:
+	go tool cgo hello.go

examples/ch2-xx/hello/_obj/_cgo_export.c

@@ -0,0 +1,58 @@
+/* Created by cgo - DO NOT EDIT. */
+#include <stdlib.h>
+#include "_cgo_export.h"
+
+extern void crosscall2(void (*fn)(void *, int, __SIZE_TYPE__), void *, int, __SIZE_TYPE__);
+extern __SIZE_TYPE__ _cgo_wait_runtime_init_done();
+extern void _cgo_release_context(__SIZE_TYPE__);
+
+extern char* _cgo_topofstack(void);
+#define CGO_NO_SANITIZE_THREAD
+#define _cgo_tsan_acquire()
+#define _cgo_tsan_release()
+
+extern void _cgoexp_16f1900c27a8_helloInt(void *, int, __SIZE_TYPE__);
+
+CGO_NO_SANITIZE_THREAD
+void helloInt(GoInt p0)
+{
+	__SIZE_TYPE__ _cgo_ctxt = _cgo_wait_runtime_init_done();
+	struct {
+		GoInt p0;
+	} __attribute__((__packed__)) a;
+	a.p0 = p0;
+	_cgo_tsan_release();
+	crosscall2(_cgoexp_16f1900c27a8_helloInt, &a, 8, _cgo_ctxt);
+	_cgo_tsan_acquire();
+	_cgo_release_context(_cgo_ctxt);
+}
+extern void _cgoexp_16f1900c27a8_helloString(void *, int, __SIZE_TYPE__);
+
+CGO_NO_SANITIZE_THREAD
+void helloString(GoString p0)
+{
+	__SIZE_TYPE__ _cgo_ctxt = _cgo_wait_runtime_init_done();
+	struct {
+		GoString p0;
+	} __attribute__((__packed__)) a;
+	a.p0 = p0;
+	_cgo_tsan_release();
+	crosscall2(_cgoexp_16f1900c27a8_helloString, &a, 16, _cgo_ctxt);
+	_cgo_tsan_acquire();
+	_cgo_release_context(_cgo_ctxt);
+}
+extern void _cgoexp_16f1900c27a8_helloSlice(void *, int, __SIZE_TYPE__);
+
+CGO_NO_SANITIZE_THREAD
+void helloSlice(GoSlice p0)
+{
+	__SIZE_TYPE__ _cgo_ctxt = _cgo_wait_runtime_init_done();
+	struct {
+		GoSlice p0;
+	} __attribute__((__packed__)) a;
+	a.p0 = p0;
+	_cgo_tsan_release();
+	crosscall2(_cgoexp_16f1900c27a8_helloSlice, &a, 24, _cgo_ctxt);
+	_cgo_tsan_acquire();
+	_cgo_release_context(_cgo_ctxt);
+}

examples/ch2-xx/hello/_obj/_cgo_export.h

@@ -0,0 +1,64 @@
+/* Created by "go tool cgo" - DO NOT EDIT. */
+
+/* package main */
+
+/* Start of preamble from import "C" comments.  */
+
+
+
+
+/* End of preamble from import "C" comments.  */
+
+
+/* Start of boilerplate cgo prologue.  */
+#line 1 "cgo-gcc-export-header-prolog"
+
+#ifndef GO_CGO_PROLOGUE_H
+#define GO_CGO_PROLOGUE_H
+
+typedef signed char GoInt8;
+typedef unsigned char GoUint8;
+typedef short GoInt16;
+typedef unsigned short GoUint16;
+typedef int GoInt32;
+typedef unsigned int GoUint32;
+typedef long long GoInt64;
+typedef unsigned long long GoUint64;
+typedef GoInt64 GoInt;
+typedef GoUint64 GoUint;
+typedef __SIZE_TYPE__ GoUintptr;
+typedef float GoFloat32;
+typedef double GoFloat64;
+typedef float _Complex GoComplex64;
+typedef double _Complex GoComplex128;
+
+/*
+  static assertion to make sure the file is being used on architecture
+  at least with matching size of GoInt.
+*/
+typedef char _check_for_64_bit_pointer_matching_GoInt[sizeof(void*)==64/8 ? 1:-1];
+
+typedef struct { const char *p; GoInt n; } GoString;
+typedef void *GoMap;
+typedef void *GoChan;
+typedef struct { void *t; void *v; } GoInterface;
+typedef struct { void *data; GoInt len; GoInt cap; } GoSlice;
+
+#endif
+
+/* End of boilerplate cgo prologue.  */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+extern void helloInt(GoInt p0);
+
+extern void helloString(GoString p0);
+
+extern void helloSlice(GoSlice p0);
+
+#ifdef __cplusplus
+}
+#endif

examples/ch2-xx/hello/_obj/_cgo_flags

@@ -0,0 +1 @@
+_CGO_CFLAGS=

examples/ch2-xx/hello/_obj/_cgo_gotypes.go

@@ -0,0 +1,70 @@
+// Created by cgo - DO NOT EDIT
+
+package main
+
+import "unsafe"
+
+import _ "runtime/cgo"
+
+import "syscall"
+
+var _ syscall.Errno
+func _Cgo_ptr(ptr unsafe.Pointer) unsafe.Pointer { return ptr }
+
+//go:linkname _Cgo_always_false runtime.cgoAlwaysFalse
+var _Cgo_always_false bool
+//go:linkname _Cgo_use runtime.cgoUse
+func _Cgo_use(interface{})
+type _Ctype_void [0]byte
+
+//go:linkname _cgo_runtime_cgocall runtime.cgocall
+func _cgo_runtime_cgocall(unsafe.Pointer, uintptr) int32
+
+//go:linkname _cgo_runtime_cgocallback runtime.cgocallback
+func _cgo_runtime_cgocallback(unsafe.Pointer, unsafe.Pointer, uintptr, uintptr)
+
+//go:linkname _cgoCheckPointer runtime.cgoCheckPointer
+func _cgoCheckPointer(interface{}, ...interface{})
+
+//go:linkname _cgoCheckResult runtime.cgoCheckResult
+func _cgoCheckResult(interface{})
+
+//go:cgo_export_dynamic helloInt
+//go:linkname _cgoexp_16f1900c27a8_helloInt _cgoexp_16f1900c27a8_helloInt
+//go:cgo_export_static _cgoexp_16f1900c27a8_helloInt
+//go:nosplit
+//go:norace
+func _cgoexp_16f1900c27a8_helloInt(a unsafe.Pointer, n int32, ctxt uintptr) {
+	fn := _cgoexpwrap_16f1900c27a8_helloInt
+	_cgo_runtime_cgocallback(**(**unsafe.Pointer)(unsafe.Pointer(&fn)), a, uintptr(n), ctxt);
+}
+
+func _cgoexpwrap_16f1900c27a8_helloInt(p0 int) {
+	helloInt(p0)
+}
+//go:cgo_export_dynamic helloString
+//go:linkname _cgoexp_16f1900c27a8_helloString _cgoexp_16f1900c27a8_helloString
+//go:cgo_export_static _cgoexp_16f1900c27a8_helloString
+//go:nosplit
+//go:norace
+func _cgoexp_16f1900c27a8_helloString(a unsafe.Pointer, n int32, ctxt uintptr) {
+	fn := _cgoexpwrap_16f1900c27a8_helloString
+	_cgo_runtime_cgocallback(**(**unsafe.Pointer)(unsafe.Pointer(&fn)), a, uintptr(n), ctxt);
+}
+
+func _cgoexpwrap_16f1900c27a8_helloString(p0 string) {
+	helloString(p0)
+}
+//go:cgo_export_dynamic helloSlice
+//go:linkname _cgoexp_16f1900c27a8_helloSlice _cgoexp_16f1900c27a8_helloSlice
+//go:cgo_export_static _cgoexp_16f1900c27a8_helloSlice
+//go:nosplit
+//go:norace
+func _cgoexp_16f1900c27a8_helloSlice(a unsafe.Pointer, n int32, ctxt uintptr) {
+	fn := _cgoexpwrap_16f1900c27a8_helloSlice
+	_cgo_runtime_cgocallback(**(**unsafe.Pointer)(unsafe.Pointer(&fn)), a, uintptr(n), ctxt);
+}
+
+func _cgoexpwrap_16f1900c27a8_helloSlice(p0 []byte) {
+	helloSlice(p0)
+}

examples/ch2-xx/hello/_obj/_cgo_main.c

@@ -0,0 +1,12 @@
+int main() { return 0; }
+void crosscall2(void(*fn)(void*, int, __SIZE_TYPE__), void *a, int c, __SIZE_TYPE__ ctxt) { }
+__SIZE_TYPE__ _cgo_wait_runtime_init_done() { return 0; }
+void _cgo_release_context(__SIZE_TYPE__ ctxt) { }
+char* _cgo_topofstack(void) { return (char*)0; }
+void _cgo_allocate(void *a, int c) { }
+void _cgo_panic(void *a, int c) { }
+void _cgo_reginit(void) { }
+#line 1 "cgo-generated-wrappers"
+int _cgoexp_16f1900c27a8_helloInt;
+int _cgoexp_16f1900c27a8_helloString;
+int _cgoexp_16f1900c27a8_helloSlice;

examples/ch2-xx/hello/_obj/hello.cgo1.go

@@ -0,0 +1,24 @@
+// Created by cgo - DO NOT EDIT
+
+//line /Users/chai/go/src/github.com/chai2010/advanced-go-programming-book/examples/ch2-xx/hello/hello.go:1
+package main
+
+//line /Users/chai/go/src/github.com/chai2010/advanced-go-programming-book/examples/ch2-xx/hello/hello.go:5
+func main() {
+	helloString("hello")
+}
+
+//line /Users/chai/go/src/github.com/chai2010/advanced-go-programming-book/examples/ch2-xx/hello/hello.go:10
+func helloInt(s int) {
+	println(s)
+}
+
+//line /Users/chai/go/src/github.com/chai2010/advanced-go-programming-book/examples/ch2-xx/hello/hello.go:15
+func helloString(s string) {
+	println(s)
+}
+
+//line /Users/chai/go/src/github.com/chai2010/advanced-go-programming-book/examples/ch2-xx/hello/hello.go:20
+func helloSlice(s []byte) {
+	println(string(s))
+}

examples/ch2-xx/hello/_obj/hello.cgo2.c

@@ -0,0 +1,31 @@
+
+
+#line 1 "cgo-gcc-prolog"
+/*
+  If x and y are not equal, the type will be invalid
+  (have a negative array count) and an inscrutable error will come
+  out of the compiler and hopefully mention "name".
+*/
+#define __cgo_compile_assert_eq(x, y, name) typedef char name[(x-y)*(x-y)*-2+1];
+
+/* Check at compile time that the sizes we use match our expectations. */
+#define __cgo_size_assert(t, n) __cgo_compile_assert_eq(sizeof(t), n, _cgo_sizeof_##t##_is_not_##n)
+
+__cgo_size_assert(char, 1)
+__cgo_size_assert(short, 2)
+__cgo_size_assert(int, 4)
+typedef long long __cgo_long_long;
+__cgo_size_assert(__cgo_long_long, 8)
+__cgo_size_assert(float, 4)
+__cgo_size_assert(double, 8)
+
+extern char* _cgo_topofstack(void);
+
+#include <errno.h>
+#include <string.h>
+
+
+#define CGO_NO_SANITIZE_THREAD
+#define _cgo_tsan_acquire()
+#define _cgo_tsan_release()
+

examples/ch2-xx/hello/hello.go

@@ -0,0 +1,22 @@
+package main
+
+import "C"
+
+func main() {
+	helloString("hello") // _GoString_
+}
+
+//export helloInt
+func helloInt(s int) {
+	println(s)
+}
+
+//export helloString
+func helloString(s string) {
+	println(s)
+}
+
+//export helloSlice
+func helloSlice(s []byte) {
+	println(string(s))
+}