C program compilation process
Compilation refers to the process of converting source code into object code, which is completed by compiler.
four phases:
Pre-processing
- Removal of Comments
- Expansion of Macros
- Expansion of the included files
- Conditional compilation
Compiling
Convert high-level code(C language) into assembly language.
Assembling
Convert assembly language into machine language.
Linking
Make code of functions which are in the library and other object files available to your main program.
Static Linking —— (.a, .lib)
Copy the code of function from other files to your object code before load.
- Speed: faster
- Space: larger
- When publishing the program, we don't need to consider whether the library files exist in the user's computer.
Dynamic Linking ——(.so, .dll)
Get the address of the function, and load the code of function at run-time. (like a pointer)
- Speed: slower
- Space: smaller
- When publishing the program, we need to consider whether the library files exist in the user's computer and whether the version is up to date.
- More independent, suitable for large-scale software development
File type
not stripped:
ELF文件中含有符号表，但是这些符号表可以用strip工具去除，这样的话这个文件就无法让debug程序跟踪了，但是会生成比较小的可执行文件。若对未连接的目标文件来说用strip去掉符号表，会导致连接器无法连接。