Talk:Coding/Guidelines

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C++

Now that we have enabled C++, I've taken the task to organize the discussion about which coding guidelines we'll need for C++. My favourite reading regarding this aspect is John Lakos "Large scale C++ projects". Ouote: "It doesn't matter which style you choose; it's important to use the chosen style consistantly."
UFO:AI is only medium scale. But it doesn't hurt to comply to those rules. --Duke 00:28, 11 April 2012 (SAST)

Participants

This should be discussed among those who consider themselves as 'current permanent contributors'. It's all about how *we* want the code to look like. The idea is to restrict the voting to those who have to suffer the most. As there are more coding styles than coders in the world, this strategy avoids endless discussions. I went through that several times, believe me :(
Invitations go out to (alphabetically):
Sandro, bayo, Duke, geever, mattn
...and as a 'technical advisor' Tron
Hmm. Do we really have that few ? :(

Strategies

We could

  • discuss and write our own guidelines from scratch (oh no)
  • adopt some published guideline (and eventually modify it a bit)
  • find a checker and/or beautifier tool and accept what it does.

I vote for the second option because the first would mean reinventing the wheel and I don't think any tool can check all the rules.

Suggestion

Googling for "coding guidelines C++" we find lots of them. I checked a few of them and found this one: http://geosoft.no/development/cppstyle.html

  • Duke's comment: With a few exceptions it describes pretty much what I did intuitively in the past. So I like it. The exceptions are rules # 28, 36, 37, 38, 40, 58, 62, 71 and 83. My favourite rule is #89. But let's see what you guys come up with.
  • Bayo's comments

Dev's discussion

  • 3
    • bayo: our struct use the convention 3 with a prefix in lower case class uiMyFunkyWidget. Maybe we can use namespace, if we decide to use it. But while we have not updated part of the code with it we should use our current naming convention. Anyway, we can use both.
    • Duke: the lowercase prefix would render rules 4 and 6 somewhat senseless. Also, except for the ui we don't have a consistent convention afaik.
      • Then ok for this rule, i thinking we have own rules about that. But then it is really need to use namespace, at least for "ui". Bayo 10:26, 21 April 2012 (SAST)
        • Uhm, don't get me wrong. Some subsystem-prefix can be useful. But it shouldn't start with lowercase. So it's "Ui" or "Uis", and "Cpg" for campaign maybe. But we should have a discussion what our subsystems are in the first place.--Duke 23:23, 23 April 2012 (SAST)
    • geever: Our type names are quite much recognizable, not a standard though. I would rather not use prefixes, but if we wanna prefix types, use the prefix we have for functions "UI_" and "CP_". I don't really like the "CpgMission_t" names, sound weird.
  • 11
    • bayo: more and more i dislike that way. IDE is quite nice now. It it not beautiful, displeasing, but if you need it to live, its ok
    • Duke: in general I dislike all those single letter pre- and suffixes. But the sideeffect for setters has some charm
    • geever: definietly NO. it's horror
    • intermediate result: we all dislike them. So does anyone have an alternative suggestion for the 'setDepth'-example ?
    • mattn: in radiant we used _name, not name_ - and it has advantages to do it that way. Yes, IDEs support you, but you see which is a member variable, and which is a local var or function parameter. So i would vote for doing _name.
  • 14
    • geever: I don't like long variable names at all, they give me more possibility to mistype them. :) Keep them as short as they can (while they are still understandable ofc.)!
      • In respect to that rule, I understand 'long variable name' as anything longer then 1-2 letters. So your statement is no contradiction to that rule.--Duke 22:12, 9 July 2012 (SAST)
    • mattn: They should not be too short, and IDEs are supporting one well enough with auto completion. But i agree, we should not make then too long.
  • 28
    • Duke: I agree with the 2nd half of that rule. But I prefer "init" instead of "initialize" and "calc" instead of "calculate"
      • I usually prefer full names. Much more readable. Bayo 10:26, 21 April 2012 (SAST)
        • Oh, I only use that for maybe a dozen *standard* abbreviations like the above. --Duke 22:14, 23 April 2012 (SAST)
    • geever: vote for short names (I wrote this to points 18 and 20, but it has a dedicated rule :) )
      • Do you mean a fixed list of say 12 common short forms like "init" or do you want a general 'licence to abbreviate' ? --Duke 22:28, 9 July 2012 (SAST)
  • 34
    • mattn: on the long run, it would be cool to have this - just to unify with radiant, but only for classes. not for the other "normal" c files.
  • 36
    • bayo: no idea, it can be problematic when fast computation is need? but most of the time we can do it
    • Duke: Disagree with that rule. Simple getters and setters should imho be inlined anyway and thus stay in the .h file.
    • geever: However sometimes I find our cpp files overstuffed with code, splitting everything to files would make our life a nightmare -- even for you who use IDEs
      • Sorry, didn't understand that. Please elaborate.--Duke 22:49, 9 July 2012 (SAST)
    • Tron:
  • 37
    • bayo: i dont like that, i prefere less newline
    • Duke: Disagree. 80 chars stems from punchcard. We have reached the age of widescreens and zoomable editors. And we don't print the code, do we ? Suggestion: The code without the comments *should* not be wider than 60 chars (think of editing on a smartphone), the whole line *must* end before 140 chars are reached.
      • BTW i dont like coment in the same line. Bayo 10:26, 21 April 2012 (SAST)
    • geever: disagree, I won't count characters when typing
    • our vote: drop rule
    • mattn: drop - but i agree with bayo - comments above the line, not after it.
  • 39
    • geever: indent rest of the line by one (tab) but don't pad the code with spaces to the matching bracket like in the example
  • 40
    • mattn: pragma once is ok, too imo.
  • 45
    • geever: not sure if it should be done every time... annoying
    • Duke: use casts only where it is needed to avoid a -Wall warning. btw do we need to use static_cast if we don't use RTTI ?
    • bayo:
  • 46
    • geever: our previous (maybe non-documented) rule was to initialize the variables the closest to their use, and I feel it more appropriate. However it is a good question where to declare variables...
  • 49
    • bayo: we are not making strong OOP software, then i dont care about this rule. struct or class is the same for me
    • Duke: it will take ages until we comply to this rule; however, it should be the goal.
    • geever: acceptable
    • Duke: new suggestion: make it a 'should' for migrated structs and a 'must' for new classes.
  • 60
    • geever: I remember a rule or recommendation to use 
      for (;;) {}
      instead. If I'm right, we have already changed some of our loops to that..
      • We have about the same amount of "while(1)" and "for(;;)". Only very few "while(true)"--Duke 23:39, 9 July 2012 (SAST)
  • 61
    • geever: I think it actually makes understanding harder as you need to track more variables in head while debugging.
      • I completely disagree. If you can assign a meaningful name to a non-trivial condition, it will enhance readability AND help debugging a lot. Try it.--Duke 23:39, 9 July 2012 (SAST)
    • mattn: i agree to duke, it can make reading code a lot easier, BUT: some statements must not be evaluated because they are not needed due to the false value of an earlier expression. Keep that in mind while extracting stuff.
  • 64
    • geever: I like shorter code, however splitting helps debugging, so I can accept it
  • 70
    • geever: We have NULL almost everywhere, and it tells me it's a pointer, so I would rather use NULL than 0.
      • mattn: NULL is not valid in the c++ context in every case. foo(NULL) calls foo(int). which is not always what you want.
  • 72
    • geever: first example as we have them now
  • 77
    • geever: gcc suggests for (init; condition; update) {} and feel it better. With a lone semicolon I have a feeling that someone accidentally cut&pasted the call, instead of copy&pasting.
    • Duke: somewhat depends on the outcome of rule #60.
    • {} is less error prone. missing the semicolon will execute the next line as loop statement. So no, i disagree to this rule.
  • 80
    • geever: our current rule suggest writing cases on the same level as the switch itself.
  • 82
    • bayo: i prefer not to use that
    • Duke: I like it, coz it saves a line with just a '}'
      • but you dislike } else { cause it save a line... Anyway my point is "put a block everywhere cause it is safer", especially when you hack the code. Bayo 10:26, 21 April 2012 (SAST)
        • No, I like "else {" because the if aligns with the else. The 'is safer'-argument is strong. And I can easily live with it.--Duke 23:02, 23 April 2012 (SAST)
    • geever: I code like this ( if possible, not in Perl ;( )
  • 87, 88, 89...
    • bayo: ugly!
    • Duke: beautiful !
      • Then, else the space, you agree with an if in 1 line, or a case in 1 line? Bayo 10:26, 21 April 2012 (SAST)
        • I general, I don't. But if it's a *series* of very similar ifs, resembling a table, it can increase readability a lot. --Duke 21:55, 23 April 2012 (SAST)
    • geever: it's horrible. It also hurts our current whitespace rules.
    • mattn: as you know - i'm a whitespace killer, i don't like this rule at all. and it does not improve readability imo. one newline is enough to mark a paragraph. there is somewhere a discussion for latex about this topic, too. and a paragraph is one newline (well, two - one empty line)
  • 92
    • bayo: but still use /** */ for method, class... bref, for the javadoc
    • Duke:
    • geever: we should use the C-ish ones only (and doxygen notation), we can still disable code with the good old #if 0
/* one lined */
/*
 * Some important
 * multiline
 */
    • mattn: good old /** */

mattn's decision

  • 10
    • bayo: more and more i dislike that way. IDE is quite nice now. It it not beautiful, displeasing, but if you need it to live, its ok
    • Duke: I'm insecure here.
    • geever: dislike
    • our vote: drop rule
    • mattn:
  • 23, 24...
    • bayo: no idea
    • Duke: imho we don't need a convention for that, so omit those two rules
      • Ok, we can take it as a "may". Bayo 10:26, 21 April 2012 (SAST)
    • geever: 24: we use Idx at multiple locations already. we can ommit them
    • our vote: drop rule
    • mattn:
  • 31
    • bayo: i prefer Color::RED
    • Duke: Color::RED looks a tad nicer, but requires discipline. COLOR_RED is forced by the compiler ;)
    • geever: I like our prefixed constants either
    • our vote: COLOR_RED
    • mattn:
  • 34
    • bayo: what we have is ok, should we really need to update everything again? Easy to do anyway, then i dont care
    • Duke: imho .h and .cpp are ok.
    • geever: .h and .cpp
    • our vote: .h and .cpp
    • mattn:
  • 38
    • bayo: i prefer TAB to align code, but i dont want special char in strings "\t" instead of " ", dont know what they talk about.
      Bayo, that rule is not about "\t". But that should be avoided too.--Duke 00:39, 19 April 2012 (SAST)
    • Duke: NO page breaks in the source. But I prefer tabs over spaces.
    • geever: our indent rule is good enough: use tabs, no page breaks
    • our vote: no page breaks, but tabs instead of spaces
    • mattn:
  • 40
    • Duke: Sure we need include guards like that. But our convention should be more like [DIR_[SUBDIR_]]CLASS_H
      • Yes, still use what we have. Bayo 10:26, 21 April 2012 (SAST)
    • geever: what we have now is good enough (don't need to overcomplicate it)
    • our vote: stick with [FILENAME]_H, prefix with [DIR_[SUBDIR_]] if not unique
    • mattn:
  • 51
    • bayo: i dislike: what's going on int* x, y, z; Is y a pointer to int? anyway i also dislike multi declaration, i prefer
int *x;
int *y;
int *z;
    • Duke: if and only if we have an additional rule that requires 'one declaration per line', I'd prefer
int* x;
int* y;
int* z;
    • geever: I prefer 
      int *x;
      and we should have a one declaration per line rule. We have it now.
    • our vote: 
      int *x;

I think we made a mistake here. As you all know, I have already changed a lot of lines to the above style. But I ran into problems: 

const teamDef_t* const td;
const teamDef_t *const td;  // ??
const teamDef_t * const td  // ????
// and
typedef aseFace_t* aseFacesIter_t;
typedef aseFace_t *aseFacesIter_t;  // doesn't look right for me

So I strongly recommend to use the "int* x;" style. --Duke 23:19, 23 May 2013 (CEST)

    • Sandro's comments (copied from IRC by Duke)

I still like type *ptr syntax. Reason: C types work this way: name some type and declare what you want to do with it. typedef works in somehow backwrds waay, but follows the same logic. type* ignores that logic, see the (in)famous int* x,y,z; example. Anyway, const problem can be fixed in most cases by switching to references :) since references are const by definition in language standard

      • Sandro, I doubt that we can switch to references in 'most' cases. 'Many' sounds more realistic to me. But however many they are, we don't have a solution for the const problem in the remaining cases.--Duke 22:02, 30 May 2013 (CEST)
    • mattn:

Indeed, this was a mistake - everything that defines a type of a variable should be grouped. This is also useful for having typedefs. Imagine the following: 

someType_t *ptr;

now you convert to: 

typedef someType_t* someTypePtr;
someTypePtr ptr;

Imo it's wrong to place a pointer of reference char to the variable - it belongs to the type. 

const someType_t* const ptr;
someType_t* const ptr;
someType_t* ptr;
someTypePtr ptr;
typedef SharedPtr<someType_t> SomeTypePtr;
SomeTypePtr ptr(new someType_t());
const someType_t& ref = getSomeRef();
someType_t& ref = otherVar;

--Mattn 09:06, 29 May 2013 (CEST)

  • 58
    • bayo: sorry i love break and continue
    • Duke: me too
    • geever: me too
    • our vote: drop rule
    • mattn:
  • 62
    • Duke: as the handling of the exception is usually much shorter, it should be handled first
      • I think it is not a strong rule anyway. Bayo 10:26, 21 April 2012 (SAST)
    • geever: drop this rule
    • our vote: drop rule
    • mattn:
  • 71
    • bayo: should be what we have now TAB=4 (it is what i use here)
    • Duke: Yes. TAB=4. As we have dropped the column width of 80, we can afford that.
    • geever: one tab (the tabsize is doesn't really matter as we're not converting them to spaces)
    • our vote: TAB=4
    • mattn:
  • 75
    • bayo: i prefer } else {
    • Duke: i prefer else {, but don't care much
      • Yes, both are readable for me Bayo 14:21, 21 April 2012 (SAST)
    • geever: I vote for } else {.
    • our vote: } else {
    • mattn:
  • 83
    • bayo: i prefer not
    • Duke: I hate it
    • geever: I hate it too
    • our vote: drop rule
    • mattn:
  • 84
    • bayo: but case 100:
    • Duke: agree with bayo
    • geever: agree, use our current rule
    • our vote: ok, but case 100:
    • mattn:
  • 85
    • bayo: i dont see why
    • Duke: Dislike it. Over-complicated. Foo(bar) is fine for me.
    • geever: agree with you: Foo(bar)
    • our vote: drop rule
    • mattn:

Other things to avoid

The google styleguide has an interesting section "Other C++ features" about things NOT to use that should be discussed. http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml

Struct

typedef struct menuNode_s {
   int blah; /**< This is a documentation comment. */    
   int a; /* armour */ /**< Calling this 'a' then putting a comment immediately after is just dumb. Don't do it; use meaningful names */
   int blahBlah; /**< The total number of blahs. */
} menuNode_t;

Can we avoid thing like int a in structs. The code looks often hard to understand. Here we can use armour. I especially thing about the inventory code. Bayo 11:21, 3 September 2010 (UTC)

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