Makefile Fundamentals

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What is? Makefile

GNU make (and other variants of make) do precisely this. make defines a language for describing the relationships between source code, intermediate files, and executables. It also provides features to manage alternate configurations, implement reusable libraries of specifications, and parameterize processes with user-defined macros.
In short, make can be considered the center of the development process by providing a roadmap of an application’s components and how they fit together.

GNU make( as well as make Other variants of ) That's what it did .make Defines a method for describing source code 、 The language of the relationship between intermediate files and executable files . It also provides management options 、 Realize the reusable specification library and parameterize the process with user-defined macros .
In short ,make It can be regarded as the center of the development process （ By providing a roadmap for the components of the application and how they are combined ）.

Programming mechanisms usually follow a fairly simple process , Edit program source file , Compile the source file into executable form , And debugging results . Here's a C The process of converting source files into executable files ：

• The preprocessor ： take .c File to .i file , The use of gcc The order is ：gcc –E, Corresponds to the preprocessing command cpp;
• compiler ： take .c/.h File conversion to .s file , The use of gcc The order is ：gcc –S, Corresponding to the compilation command cc –S;
• Assembler ： take .s File to .o file , The use of gcc The order is ：gcc –c, The corresponding assembly command is as;
• The linker ： take .o Convert files into executable programs , The use of gcc The order is ： gcc, The corresponding link command is ld;
• loader ： Load the executable program into memory and execute ,loader and ld-linux.so.

make Is a build tool , Through analysis makefile The description inside , Compile and build the whole project .

Tips ： The following is the main body of this article , The following cases can be used for reference

One 、 Why use Makefile

make There are two main problems to solve ：

1. Relationship maintenance of a large amount of code

There are many source codes in large projects , Manual maintenance 、 Long compilation time and complex compilation commands , Difficult to remember and maintain

Write the code maintenance command and compilation command in makefile In file , And then use make The tool parses this file and automatically executes the corresponding command , It can realize the reasonable compilation of code

2. Reduce repeated compilation time

n When changing one of the files , Can determine which files have been modified , You can recompile only this file , Then re link all the target files , Save compilation time

Two 、Makefile Basic grammar

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