C Isn't a Programming Language Anymore

Re:C Isn't a Programming Language Anymore by fweimer on Monday November 07, 2022 @03:18PM (#33511776)

I would even go as far as to say that a good OS ABI only uses a safe subset of C. This excludes pass-by-value structs (and vector types), struct returns, and maybe even bitfields.

Even with these restrictions in place, modern register-based calling conventions can be still be rather complex, but these restrictions reduce it somewhat. They help to avoid areas in which implementations traditionally diverge, too.

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Re:C Isn't a Programming Language Anymore by cryptonector on Monday November 07, 2022 @04:32PM (#33512803)

What's wrong with pass-by-value structs? Yes, I'm aware that long ago there was a problem on SPARCs where Sun Studio and GCC handled struct value returns differently, but not pass-by-value. ABIs can and do define how to do pass by value of values of struct types.

The bits of C that need to be avoided in APIs are:

  - bitfields unless no bitfield crosses a
    byte boundary
  
  - struct fields of enum types (because the
    size of the enum type is implementation
    specific)

The spec should fix this, damnit.

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