And yet again, I miss Borland’s compiler

Comments 6

1. I guess your installation of ICC is broken because normally size_t is defined. Another explanation would be that the configure script calls the compiler with options that are not compatible with icc.

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2. I’ve just used emerge icc to install it, so if it’s broken, the ebuild is broken most likely. I doubt it’s any option because it fails during the first compiler’s sanity check, but I’ll doublecheck tomorrow for safety.

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3. Do you know about pure functions in GCC?http://gcc.gnu.org/onlinedo…Theoretically marking such functions as pure manually should allow the compiler to be able to optimize them away if unused. Not sure if it actually does, but…To quote the GCC manual:Many functions have no effects except the return value and their return value depends only on the parameters and/or global variables. Such a function can be subject to common subexpression elimination and loop optimization just as an arithmetic operator would be. These functions should be declared with the attribute pure. For example, int square (int) __attribute__ ((pure));says that the hypothetical function square is safe to call fewer times than the program says.Some of common examples of pure functions are strlen or memcmp. Interesting non-pure functions are functions with infinite loops or those depending on volatile memory or other system resource, that may change between two consecutive calls (such as feof in a multithreading environment).The attribute pure is not implemented in GCC versions earlier than 2.96.

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4. I know that Mart, and I did note that 😉

   *Pure* and *constant* functions should be optimised away, but for functions the compiler has no clue about (which is the common status for non-static functions unless you tell it otherwise) the call is still executed, as it might change the global state variables.

   [Emphasis added]Unfortunately most of custom functions for programs are not marked as pure or constant even though they are for the simple reason that not everybody likes messing with compilers’ attributes. Thus the problem is still there.

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5. Mart Raudsepp wrote:”Many functions have no effects except the return value and their return value depends only on the parameters and/or global variables.””Some of common examples of pure functions are strlen”This is contradicting. strlen is not pure according to that definition. It takes the parameter const char *s. But the return value does not only depend on the value of s and global variables. It also depends on the content of the memory location pointed to by s (and the following locations until the terminator). The content of those memory locations can of course change between calls to strlen with the same value of s. If s is allowed to point to something else than a global variable including a terminator (which it is), then it is proven that strlen is not pure.

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6. @strlen()@ is indeed not a pure function, it’s a constant function though. The compiler can still optimise it, but not as much as a pure function.Indeed, the fact that @strlen()@ is non-pure (but constant) is what makes it important to not call it multiple time with the same (non-static) parameter.

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