Mach-O

Mach-O是Mach object缩写，是mac/ios上用于存储程序、库的标准格式

https://developer.apple.com/library/archive/navigation/

常见类型

• MH_OBJECT
  • 目标文件(.o)
  • 静态库(.a) 静态库其实就是多个.o合并在一起
• MH_EXECUTE
  • 可执行文件
• MH_DYLIB
  • 动态库文件(.dylib .framework)
• MH_DYLINKER
  • 动态链接编辑器 dyld
• MH_DSYM
  • 存储着二进制文件符号信息的文件

Mach-O 组成

https://developer.apple.com/library/archive/documentation/DeveloperTools/Conceptual/MachOTopics/0-Introduction/introduction.html

A Mach-O file has the following regions of data (the complete format is described in OS X ABI Mach-O File Format Reference):

• Header: Specifies the target architecture of the file, such as PPC, PPC64, IA-32, or x86-64.
  文件类型、目标架构类型等
• Load commands: Specify the logical structure of the file and the layout of the file in virtual memory.
  描述文件在虚拟内存中的逻辑结构、布局
• Raw segment data: Contains raw data for the segments defined in the load commands.
  在load commands.中定义的Segment的原始数据

dyld

dyld用于加载以下类型的Mach-O文件

• MH_EXECUTE
• MH_DYLINKER
• MH_BUNDLE

App的可执行文件、动态库都是由dyld负责加载的