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I know that the most recent versions of POSIX specify that a C99-compliant compiler should (optionally) be present and called c99. Similarly, older versions of POSIX used to specify an optional c89 command to exist as part of the "C-Language Development Utilities".

However, I'm having a hard time finding any reference to cc. Is this command mentioned somewhere in the POSIX standard or just a convention?

Jeff Schaller
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Stefano Sanfilippo
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  • It's leftover from the original C compilers and reluctance to use **`c89`** when the two (cc/c89) were considered to be the same thing. Finding an authoritative source for that will be hard, since the POSIX documentation eliminates most of the historical information. – Thomas Dickey Jul 16 '17 at 20:29

1 Answers1

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The original POSIX 1003.1 (published in 1988) specified a cc utility. The Single Unix Specification version 2 (1997) included both cc and c89. The name c89 was introduced to be a standard dialect of C. The name cc was kept but marked as legacy and declared to be an unspecified dialect of C. Many vendors shipped a compiler that defaulted to K&R C (i.e. pre-ANSI C) under the name cc. You might note that cc is mandatory while c89 is part of the C language development option. It was common to have a C compiler under the name cc that was only really capable of compiling kernel drivers, and commercial unices often charged extra for a proper C compiler.

POSIX 1003.1-2001 (Single Unix v3) specifies c99 specifies instead of c89, to use an updated standard dialect of C. You can see some editorial traces left from a draft that included a cc utility as well, but cc was removed from the specification. POSIX 1003.1-2008 (Single Unix v4) again just has c99

Gilles 'SO- stop being evil'
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    So, if I understand correctly, by removing `cc` they made a C compiler optional as part of the "C-Language Development Utilities" instead of required? – Stefano Sanfilippo Jul 28 '17 at 14:53
  • That's a very good and well-researched answer! I wonder why later versions of POSIX didn't specify `c11` or `c17` - they all seem to have stuck with `c99`. – AJM Jun 24 '21 at 15:37
  • (And those "editorial traces" were causing me quite a bit of confusion - thanks for clearing it up.) – AJM Jun 24 '21 at 15:37