Well that's unfortunate because that would have been acceptable to me.
On Wed, Oct 10, 2012 at 11:03 PM, Campbell Barton <[email protected]> wrote: > Checked, and that would work in MSVC since its the same warning that > checks a function matches its declaration in the header, > so turning that off isn't an option (was thinking it may have been a > different warning ID). > > > On Thu, Oct 11, 2012 at 12:45 AM, Campbell Barton <[email protected]> > wrote: >> @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 > > > > -- > - 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
