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What are the stages of C compilation?

C compilation goes through several stages. For clang, the C compiler on my machine, these are:

+----+        +----+           +-----+       +---------+       +----+       +----+       +-----------+
| .c |--cpp-->| .i |--parser-->| AST |--??-->| LLVM IR |--??-->| .s |--as-->| .o |--ld-->| a.out/.so |
+----+        +----+           +-----+       +---------+       +----+       +----+       +-----------+
  1. Take main.c, preprocess to produce tokens (a .i file). This is done by the C preprocessor, cpp.
  2. Take tokens, parse into AST.
  3. Take AST, produce LLVM IR (“Intermediate Representation”).
  4. Take LLVM IR, produce assembly (a .s file).
  5. Take assembly, produce object file (a .o file). This is done by the assembler, as.
  6. Take object file, produce executable (a.out) or dynamic library (.so).

I’ll cover these stages in future posts.

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After months of secret toil, I and Andrew Carr released Everyday Data Science, a unique interactive online course! You’ll make the perfect glass of lemonade using Thompson sampling. You’ll lose weight with differential equations. And you might just qualify for the Olympics with a bit of statistics!

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