@Jason, wouldn't it work to remove offending const from headers and disable the warning in MSVC?
On Wed, Oct 10, 2012 at 9:57 PM, Jason Wilkins <[email protected]> wrote: > C is ALWAYS call by value and C++ is call by value by default there is > no need to mark the parameters const to know it will not change the > caller's value in that case. The const on a call by value function > parameter is an internal detail of the function itself. The function > is saying that it won't change its copy. To the caller this is like > function saying what kind of magazines are hidden under its mattress. > > I do agree that C# is nice in that you have to mark a parameter as > 'ref' both in the interface and at each call site (same with having to > declare a shadowing variable as 'shadow'). However imagine if you had > to prefix 'val' every time you called the function even though that is > the default. That would be very ugly and unneeded. That sort of > thing would be similar to what I'm arguing against here. > > I've made my case though, so if people disagree I'll just have to live > with their code. I won't belabor the point any more. > > On Tue, Oct 9, 2012 at 3:02 PM, Dahlia Trimble <[email protected]> > wrote: >> I don't poke around much in blender source but I've found in c++ in general >> that I kind of like being able to declare a function parameter as const, >> for the simple reason that I don't see well and it helps me easily >> differentiate foo(const int bar) from foo(int& bar). Where in the latter I >> might not notice it's a reference. >> >> I like how C# handles references: if you declare a function you need to use >> the ref keyword both in the declaration and when calling the function. This >> way you cannot call a function that may modify a passed parameter without >> explicitly stating that you are aware it's passed by reference. I think c++ >> could use something similar. >> >> >> On Sun, Oct 7, 2012 at 10:17 PM, Jason Wilkins >> <[email protected]>wrote: >> >>> OK, when I get warnings I guess I will fix them by adding the const in >>> the appropriate spot. At least this kind of const is not viral :) >>> >>> On Sun, Oct 7, 2012 at 9:55 AM, Campbell Barton <[email protected]> >>> wrote: >>> > On Mon, Oct 8, 2012 at 1:26 AM, Jason Wilkins <[email protected]> >>> wrote: >>> >> I probably would not notice except that it is done inconsistently and >>> >> I get lots of warnings. I tend to fix things by removing the const >>> >> though. >>> >> >>> >> Another thing I noticed was returning a const pointer from a function >>> >> but then expecting to free it using 'free'. Dynamically allocated >>> >> memory is not 'const' for the purposes of 'free'. It would probably >>> >> be better to cast away the const inside a special function instead of >>> >> asking the user to use a raw 'free'. (or just not use const). >>> > agree, const can be a bit of a pain like this. >>> > >>> >> I'm all for using const, but I really question if making primitive >>> >> arguments const is more trouble than it is worth. I mean, to follow >>> >> through on it would be a huge task. It only generates a warning (no >>> >> error) when done inconsistently and if you change your mind now you >>> >> have to make a change in two places instead of one. >>> > >>> > You dont need to follow it though, if a dev wants to use it, they can, >>> > when done inconsistently it wont give warnings in GCC - but this stuff >>> > is really issue with multi-platform dev, it happens in other areas too >>> > - I often wake up to find blender wont compile because of an error in >>> > some commit from a dev with a different environment (-Werror helps >>> > here too :) ). >>> > you can correct warnings, or mail some other dev to fix, last I >>> > compiled on MSVC I didnt see any warnings like this though (a few >>> > weeks back). >>> > >>> >> To me this is a C programmers version of those people who have to turn >>> >> a light switch on and off a prime number of times. >>> >> >>> >> Reason #5 would be that it is just cluttered and ugly. It decreases >>> >> readability instead of enhancing it. It reminds me of when I had a >>> >> phase where I wanted to add 'struct' to everything so that people knew >>> >> that, yes, this is a struct. >>> > >>> > think this comes down to personal preference, if you think its not >>> > warranted, don't add it to your code. >>> > >>> >> I guess detecting stack corruption does not seem like a plus to me >>> >> because my environment does this very aggressively without help >>> >> (MSVC). >>> > >>> > Its no protection against stack corruption, >>> > It just means you know the var wont change under normal conditions, if >>> > it does change that something exceptional/wrong is happening. >>> > >>> >> On Sun, Oct 7, 2012 at 8:22 AM, Campbell Barton <[email protected]> >>> wrote: >>> >>> On Sun, Oct 7, 2012 at 8:25 PM, Jason Wilkins < >>> [email protected]> wrote: >>> >>>> If I had a function with the prototype: foo(int bar) >>> >>>> >>> >>>> It may be tempting to declare the it as: foo(const int bar) >>> >>>> >>> >>>> The reason would be that bar is not modified inside of foo, so by >>> >>>> declaring it this way we prevent ourselves from accidentally modifying >>> >>>> it. >>> >>>> >>> >>>> This is not idiomatic C, and for good reasons. >>> >>>> >>> >>>> 1) We use 'const' on pointers to indicate that we are not going to >>> >>>> modify what is pointed at, when a programmer sees 'const int' it is >>> >>>> momentarily confusing because we expect 'const int*' >>> >>>> >>> >>>> 2) This exposes internal details of the function to the outside world. >>> >>>> The fact that 'bar' is const in this case is not actually a part of >>> >>>> the interface of that function. >>> >>>> >>> >>>> 3) If we change our minds later and actually do want to modify the >>> >>>> copy of 'bar' inside the function then we have to change the interface >>> >>>> again, but as per #2 it actually has nothing to do with the user of >>> >>>> 'foo' >>> >>>> >>> >>>> 4) It is just not idiomatic. Looking at it is like listening to a >>> >>>> foreigner speak your native language in "creative" ways. >>> >>>> >>> >>>> I have not figured out who is doing this, but please stop :) >>> >>> >>> >>> I've been doing this and Im not convinced its a bad thing, in some >>> >>> functions its a good hint that a var is `fixed` and shouldn't be >>> >>> changed. >>> >>> If a dev wants to change it they can just remove the `const` but it >>> >>> means they think twice before doing it (as in - maybe there is a good >>> >>> reason it shouldn't be changed). >>> >>> >>> >>> The main reason I like to have this sometimes is when debugging you >>> >>> know for sure a var wont change, if it does - its a buffer overflow or >>> >>> something exceptional. >>> >>> Often its not really an issue - but there are cases it can help verify >>> >>> whats going on when reading the function. >>> >>> >>> >>> That the `const` gets in the header is a little inconvenience if it >>> >>> changes often - but IMHO changing those is rare enough that its not an >>> >>> issue. >>> >>> _______________________________________________ >>> >>> Bf-committers mailing list >>> >>> [email protected] >>> >>> http://lists.blender.org/mailman/listinfo/bf-committers >>> >> _______________________________________________ >>> >> Bf-committers mailing list >>> >> [email protected] >>> >> http://lists.blender.org/mailman/listinfo/bf-committers >>> > >>> > >>> > >>> > -- >>> > - Campbell >>> > _______________________________________________ >>> > Bf-committers mailing list >>> > [email protected] >>> > http://lists.blender.org/mailman/listinfo/bf-committers >>> _______________________________________________ >>> Bf-committers mailing list >>> [email protected] >>> http://lists.blender.org/mailman/listinfo/bf-committers >>> >> _______________________________________________ >> Bf-committers mailing list >> [email protected] >> http://lists.blender.org/mailman/listinfo/bf-committers > _______________________________________________ > Bf-committers mailing list > [email protected] > http://lists.blender.org/mailman/listinfo/bf-committers -- - Campbell _______________________________________________ Bf-committers mailing list [email protected] http://lists.blender.org/mailman/listinfo/bf-committers
