Use of gcc/g++

Catalog

1. What is? gcc/g++？

2. gcc How to complete the conversion ？

1. Preprocessing

2. compile

3. assembly

 4. link

Library is divided into static library and dynamic library

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1. What is? gcc/g++？

gcc/g++ It's a compiler , Used to put C/C++ Language into machine language

2. gcc How to complete the conversion ？

Format ：gcc [ Options ] Compiled files [ Options ] [ Target file ]

If it goes directly gcc  [ Compile the file ] -o [ Target file ], The executable file will be directly generated

gcc Converting high-level language into machine language is divided into four steps ：

1. Preprocessing

Pretreatment mainly includes four steps

• Expansion of header file
• Macro replace
• Note replacement
• Conditional compilation

Format ：gcc -E test.c -o test.i

 

  We can see that the pretreatment phase has completed all the steps we have mentioned

2. compile

The main function of compilation is to convert high-level language into assembly language

Format ：gcc -S test.i -o test.s

  Assembly language is more concise than high-level language

3. assembly

The most important step of compilation is to convert assembly language into binary language , That is, the machine recognizable code

Format ：gcc -c test.s -o test.o

 4. link

It's generating .o The end of the file marks the successful compilation , Then we need to link

Format ：gcc test.o -o test

 

  Here we need to cover an important knowledge point , That's why we link ？

We have compiled our code successfully , What is the role of links ？

  We can find that in the code we write , Contains printf function , and print Is this function implemented by us ？ Obviously not , Then we need to complete the implementation of this function when calling this function , And because we didn't complete the implementation of this function , But this function is implemented in the Library , Therefore, when we link, we are the linked libraries , So that we can complete the operation .

Library is divided into static library and dynamic library

Static library Refers to when compiling Links , Add all the implemented function code into the executable , Therefore, the generated file is relatively large , But in operation, there is no need to link library functions

Dynamic library Refers to when compiling Links , The implemented function code is not added to the executable , Instead, the required libraries are linked during the link , This can save space

stay Linux in , The default link is the dynamic library

  And we can also actively link to static libraries

  We found that when linking static libraries , The memory size is almost linked to the dynamic library 100 times

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