"Kevin P. Fleming" <kpfleming@xxxxxxxxxx> writes: > On 01/17/2011 05:56 PM, Jonathan Wakely wrote: >> On 17 January 2011 23:04, tom fogal wrote: >>> I have a function with this prototype: >>> >>> void to_3d(hsize_t index, const hsize_t dims[3], hsize_t outdex[3]); >>> >>> The effect of the function is to store appropriate values in the >>> "outdex" array. It does not read or write global memory. >>> >>> I would like to mark this as __attribute__((const)), but it doesn't >>> quite fit the definition, as it's a void function. Obviously I can't >>> just change it to make `outdex' the return value, since outdex is an >>> array. >> >> Isn't outdex actually a pointer? That's another reason the function >> can't be marked const. > > It's a pointer, but the pointer is caller-provided, so I would think > the compiler could make a reasonable assumption that it "knows" the > only memory locations the called function is going to be able to > modify if it is marked 'const'. The documentation is clear that a function with a pointer argument may not be declared as const, but it may be declared as pure. E.g., the strlen function is pure but not const. Ian
