C Program Execution

Abstract

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• Convert from C program to Instruction, then execute it as a Process (进程)

5 Steps

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Stage 1

• Preprocessor generates expanded .I file
• Process Pre-processor Directives
• Replace all the C Macro in the Header File & program files
• Would’t complain about missing Header File
• Remove spaces, new lines & comments

gcc -E hello_world.c

Stage 2

• Compiler generates codes in Assembly language in .s format
• Returns error & warnings if the Header File isn’t defined

gcc -S hello_world.c

Stage 3

• Assembler generate Instruction in .o format
• Essential for code sharing and dynamic linking in software development.

gcc -c hello_world.c

Stage 4

• Linker Link up with other Instruction which are dependencies of the program we wrote
• Sometimes we will break the program into many different c files, then run compiler on each, and link up all. This is for easier management & debugging
• Output executable format or library file
• We can use ldd to show the dependencies
• Will return error if unable to link up some of the required .o files

Stage 5

• Loader loads the executable from Disk to Main Memory to create a Process (进程)

References

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• C Language Source Code to EXE
• [Modern OS - 1.8.3 Large Programming Projects](https://csc-knu.github.io/sys-prog/books/Andrew%20S.%20Tanenbaum%20-%20Modern%20Operating%20Systems.pdf#Large Programming Projects)