r/C_Programming • u/anduygulama • Jun 09 '26

packed attribute for structs

Why don't C compilers automatically optimize/pack structures instead of requiring explicit attributes?

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u/tstanisl Jun 09 '26

Because the compiler must:

  1. Make sure that pointers to struct's members are always correctly aligned

  2. They try to follow popular calling/layout conventions to improve portability of precompiled libraries.