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Software Engineering

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  • Well, sure there is nothing wrong with coding C standard X + extensions Y and Z, as long as that gives you significant advantages, you know you did that, and you thoroughly documented it. Sadly, all three conditions are normally not met, and thus it's fair to say the code is broken. Commented Jun 27, 2016 at 12:12
  • @Deduplicator: C89 compilers were promoted as being upwardly-compatible with their predecessors, and likewise for C99, etc. While C89 imposes no requirements on behaviors which had previously been defined on some platforms but not others, upward compatibility would suggest that C89 compilers for platforms that had regarded behaviors as defined should continue to do so; the rationale for the promotion of short unsigned types to signs would suggest that the authors of the Standard expected compilers to behave that way whether or not the Standard mandated it. Further... Commented Jun 27, 2016 at 15:28
  • ...strict interpretation of the aliasing rules would throw upward compatibility out the window and make many kinds of code unworkable, but a few slight tweaks (e.g. identifying some patterns where cross-type aliasing should be expected and therefore permissible) would solve both problems. The whole stated purpose of the rule was to avoid requiring compilers to make "pessimistic" aliasing assumptions, but given "float x", should a presumption that "foo((int*)&x)" might modify x even if "foo" doesn't write to any pointers of type 'float*" or "char*" be considered "pessimistic" or "obvious"? Commented Jun 27, 2016 at 15:41