iOS:动态库

作者: MonKey_Money | 来源:发表于2021-01-25 15:16 被阅读0次

1.动态库原理

1.1自己生成动态库(失败)

我们还是用在静态库中的TestExample案例先生成动态库

image.png
为了方便我们使用创建build.sh，来使用脚本

clang -target x86_64-apple-macos11.0.1 \
-fobjc-arc \
-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk \
-I./dylib \
-c test.m -o test.o

pushd ./dylib
echo "编译TestExample.m --- TestExample.o"
clang -target x86_64-apple-macos11.0.1 \
-fobjc-arc \
-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk \
-c TestExample.m -o TestExample.o
clang -dynamiclib \
-target x86_64-apple-macos11.0.1 \
-fobjc-arc \
-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk \
TestExample.o -o libTestExample.dylib
echo "编译TestExample.m --- libTestExample.dylib"
clang -target x86_64-apple-macos11.0.1 \
-fobjc-arc \
-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk \
-L./dylib \
-lTestExample \
test.o -o test

运行后报错还是和上面一样 dyld: Library not loaded: libTestExample.dylib

1.2.先生成静态库再链接成动态库

//把我们的o文件变成a文件。也可以使用ar -rc a.a a.o
libtool -static -arch_only x86_64 TestExample.o -o libTestExample.a

ld -dylib -arch x86_64 \
-macosx_version_min 11.0 \
-syslibroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk \
-lsystem -framework Foundation \
-all_load \  //如果没有这个参数，链接器会默认not all load
libTestExample.a -o libTestExample.dylib

运行之后还是报错

Process 25266 launched: '/Users/MacW/Desktop/loginlearn/强化版/强化班-4-动态库/上课代码/动态库原理/test' (x86_64)
dyld: Library not loaded: libTestExample.dylib
  Referenced from: /Users/MacW/Desktop/loginlearn/强化版/强化班-4-动态库/上课代码/动态库原理/test
  Reason: image not found

错误显示库没有加载进来
我们查看test加载所需要的动态库

otool -l test | grep 'DYLIB' -A 5
//日志如下
 cmd LC_LOAD_DYLIB
      cmdsize 48
         name libTestExample.dylib (offset 24)
   time stamp 2 Thu Jan  1 08:00:02 1970
      current version 0.0.0
compatibility version 0.0.0
--
          cmd LC_LOAD_DYLIB
      cmdsize 96
         name /System/Library/Frameworks/Foundation.framework/Versions/C/Foundation (offset 24)
   time stamp 2 Thu Jan  1 08:00:02 1970
      current version 1770.106.0
compatibility version 300.0.0
--
          cmd LC_LOAD_DYLIB
      cmdsize 56
         name /usr/lib/libobjc.A.dylib (offset 24)
   time stamp 2 Thu Jan  1 08:00:02 1970
      current version 228.0.0
compatibility version 1.0.0
--
          cmd LC_LOAD_DYLIB
      cmdsize 56
         name /usr/lib/libSystem.B.dylib (offset 24)
   time stamp 2 Thu Jan  1 08:00:02 1970
      current version 1292.0.0
compatibility version 1.0.0
--
          cmd LC_LOAD_DYLIB
      cmdsize 104
         name /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation (offset 24)
   time stamp 2 Thu Jan  1 08:00:02 1970
      current version 1770.106.0
compatibility version 150.0.0

我们看到我们自己创建的库 name libTestExample.dylib (offset 24)，而其他的动态库的name确实库的路径。
我们的动态库能够自己保存自己的路径

otool -l ./dylib/libTestExample.dylib | grep 'ID' -A 5
//-A是向下寻找5行，-B是向上查找
 cmd LC_ID_DYLIB
      cmdsize 48
         name libTestExample.dylib (offset 24)
   time stamp 1 Thu Jan  1 08:00:01 1970
      current version 0.0.0
compatibility version 0.0.0
--
     cmd LC_UUID
 cmdsize 24
    uuid F26CDB5B-F71B-3658-86BE-C93CBE279ABE
Load command 9
       cmd LC_BUILD_VERSION
   cmdsize 32

我们看到name 还是 libTestExample.dylib
我们可以使用install_name_tool去给动态库添加路径

man install_name_tool
NAME
       install_name_tool - change dynamic shared library install names

install_name_tool就是改变动态的路径。
给动态路添加路径

install_name_tool -id /Users/MacW/Desktop/loginlearn/强化版/强化班-4-动态库/上课代码/动态库原理/dylib/libTestExample.dylib  libTestExample.dylib

重新查看动态库的LC_ID_DYLIB

otool -l libTestExample.dylib | grep 'ID' -A 5
 cmd LC_ID_DYLIB
      cmdsize 144
         name /Users/MacW/Desktop/loginlearn/强化版/强化班-4-动态库/上课代码/动态库原理/dylib/libTestExample.dylib (offset 24)
   time stamp 1611538070 Mon Jan 25 09:27:50 2021
      current version 0.0.0
compatibility version 0.0.0
--
     cmd LC_UUID
 cmdsize 24
    uuid F26CDB5B-F71B-3658-86BE-C93CBE279ABE
Load command 9
       cmd LC_BUILD_VERSION
   cmdsize 32

然后重新编译和链接我们的test文件运行成功
我们通过install_name_tool，重新给编译过的动态库加的路径，其实ld提供给我们一个参数可以直接加的install_name
所以我们初期的sh脚本如下

clang -target x86_64-apple-macos11.0.1 \
-fobjc-arc \
-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk \
-I./dylib \
-c test.m -o test.o

pushd ./dylib
echo "编译TestExample.m --- TestExample.o"
clang -target x86_64-apple-macos11.0.1 \
-fobjc-arc \
-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk \
-c TestExample.m -o TestExample.o

echo "编译TestExample.o --- libTestExample.a"

# Xcode->静态库
libtool -static -arch_only x86_64 TestExample.o -o libTestExample.a
# -dynamiclib: 动态库
# dylib 最终链接产物 -》
ld -dylib -arch x86_64 \
-macosx_version_min 11.0 \
-syslibroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk \
-lsystem -framework Foundation \
-install_name /Users/MacW/Desktop/loginlearn/强化版/强化班-4-动态库/上课代码/动态库原理/dylib/libTestExample.dylib \
-all_load \
libTestExample.a -o libTestExample.dylib
popd
echo "链接libTestExample.dylib -- test EXEC"
clang -target x86_64-apple-macos11.0.1 \
-fobjc-arc \
-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk \
-L./dylib \
-lTestExample \
test.o -o test

运行没问题

2.动态库复用性

我们在上面指定的路径是我们的绝对路径，如果动态库换了位置，很明显还是会出现之前出现的问题， Reason: image not found

2.1@rpath解决绝对路径的困扰

@rpath
Runpath search Paths
dyld搜索路径
运行时@rpath指示dyld按顺序搜索路径列表，以找到动态库。
@rpath保存一个或多个路径的变量
所以我们修改脚本

-install_name @rpath/dylib/libTestExample.dylib

运行还是报错，为什么呢？我们可以查看test文件是否有rpath的设置

2.2 rpath

otool -l  test | grep 'RPATH' -A 5

我们通过install_name_tool给test添加rpath路径

 install_name_tool -add_rpath /Users/MacW/Desktop/loginlearn/强化版/强 化班-4-动态库/上课代码/动态库原理 test

正常运行。但是add_rpath也是我们手动添加的，没有可复用性。

2.3.executable_path和loader_path

@executable_path:表示可执行程序所在的目录，解析为可执行文件的绝对路径。
@loader_path:表示被加载的Mach-O 所在的目录，每次加载时，都可能被设置为不同的路径，由上层指定。

install_name_tool -rpath /Users/MacW/Desktop/loginlearn/强化版/强化班-4-动态库/上课代码/动态库原理  @executable_path test

运行test成功

3.动态库链接动态库

test.m文件使用Frameworks中的TestExample.framework
在TestExample.framework库中使用TestExampleLog.framework

3.1先编译并链接TestExampleLog.framework

clang -target x86_64-apple-macos11.0.1 \
-fobjc-arc \
-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk \
-I./Headers \
-c TestExampleLog.m -o TestExampleLog.o

clang -dynamiclib  \
-target x86_64-apple-macos11.0.1 \
-fobjc-arc \
-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk \
-Xlinker -install_name -Xlinker @rpath/TestExampleLog.framework/TestExampleLog \
TestExampleLog.o -o TestExampleLog

install_name是提供给外部需要链接TestExampleLog的路径。
通过查看otool -l TestExampleLog | grep 'ID' -A 5能看出外部需要链接的路径

          cmd LC_ID_DYLIB
      cmdsize 72
         name @rpath/TestExampleLog.framework/TestExampleLog (offset 24)
   time stamp 1 Thu Jan  1 08:00:01 1970
      current version 0.0.0
compatibility version 0.0.0
--
     cmd LC_UUID
 cmdsize 24
    uuid 73F8F987-0378-346D-B014-890611B76871
Load command 9
       cmd LC_BUILD_VERSION
   cmdsize 32

3.2.再编译链接TestExample.framework

clang -target x86_64-apple-macos11.0.1 \
-fobjc-arc \
-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk \
-I./Headers \
-I./Frameworks/TestExampleLog.framework/Headers \
-c TestExample.m -o TestExample.o

clang -dynamiclib  \
-target x86_64-apple-macos11.0.1 \
-fobjc-arc \
-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk \
-Xlinker -install_name -Xlinker @rpath/TestExample.framework/TestExample \
-Xlinker -rpath -Xlinker @loader_path/Frameworks \
-F./Frameworks \
-framework TestExampleLog \
TestExample.o -o TestExample


echo "-------DYLIB---------"
otool -l TestExample | grep 'DYLIB' -A 5
echo "-------ID---------"
otool -l TestExample | grep 'ID' -A 5

install_name是提供给调用者加载的路径
rpath是提供给调用TestExampleLog的初始路径

3.3编译并链接test

clang -target x86_64-apple-macos11.0.1 \
-fobjc-arc \
-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk \
-I./Frameworks/TestExample.framework/Headers \
-c test.m -o test.o

clang   \
-target x86_64-apple-macos11.0.1 \
-fobjc-arc \
-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk \
-Xlinker -rpath -Xlinker @executable_path/Frameworks \
-F./Frameworks \
-framework TestExample \
test.o -o test

运行正常打印

3.4.test文件怎么使用TestExampleLog

如果我们想使用TestExampleLog，我们需要能再TestExample中导出符号中能看到TestExampleLog

objdump --macho --exports-trie TestExample
TestExample:
Exports trie:
0x000080C0  _OBJC_METACLASS_$_TestExample
0x000080E8  _OBJC_CLASS_$_TestExample

我们没有看出有导出符号，所以我们无法在test使用TestExampleLog，我们需要使用reexport_framework
我们修改TestExample内的脚本

clang -dynamiclib  \
-target x86_64-apple-macos11.0.1 \
-fobjc-arc \
-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk \
-Xlinker -install_name -Xlinker @rpath/TestExample.framework/TestExample \
-Xlinker -rpath -Xlinker @loader_path/Frameworks \
-Xlinker -reexport_framework -Xlinker TestExampleLog \
-F./Frameworks \
-framework TestExampleLog \
TestExample.o -o TestExample

查看DYLIIB信息

 otool -l TestExample | grep 'DYLIB' -A 5
  cmd LC_ID_DYLIB
      cmdsize 72
         name @rpath/TestExample.framework/TestExample (offset 24)
   time stamp 1 Thu Jan  1 08:00:01 1970
      current version 0.0.0
compatibility version 0.0.0
--
          cmd LC_REEXPORT_DYLIB
      cmdsize 72
         name @rpath/TestExampleLog.framework/TestExampleLog (offset 24)
   time stamp 2 Thu Jan  1 08:00:02 1970
      current version 0.0.0
compatibility version 0.0.0

可以知道TestExample重新加一个cmd，LC_REEXPORT_DYLIB
我们在test中导入头文件

#import <Foundation/Foundation.h>
#import "TestExample.h"
#import "TestExampleLog.h"

int main(){
    NSLog(@"testApp----");
    TestExample *manager = [TestExample new];
    [manager lg_test: nil];
    TestExampleLog *log = [TestExampleLog new];
    NSLog(@"testApp----%@",log);
    return 0;
}

我们的脚本文件也需要-I头文件，重新运行脚本，正常打印。

iOS:动态库

1.动态库原理

1.1自己生成动态库(失败)

1.2.先生成静态库再链接成动态库

2.动态库复用性

2.1@rpath解决绝对路径的困扰

2.2 rpath

2.3.executable_path和loader_path

3.动态库链接动态库

3.1先编译并链接TestExampleLog.framework

3.2.再编译链接TestExample.framework

3.3编译并链接test

3.4.test文件怎么使用TestExampleLog

相关文章

网友评论

延伸阅读

深度阅读

栏目导航

热点阅读

iOS小技巧