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I have a project in C (don't ask why but it needs to be in C), where I need to track multiple pieces of data and commands for different modules. Some actions that the program will take depend on the interactions between these different pieces of data (eg. if foo == 3 and bar == 4 do X, otherwise do Y). Some of these pieces of data will be structs grouping together similar information, some will just be primitives.

I am wondering what the best way to implement this would be. Personally, I think that each piece of data should be its own variable like so:

static int module_state;
static M1_Data module_1_data;
static int last_m1_command;
static M2_Data module_2_data;
etc...

One of my coworkers is suggesting instead that I manage everything in a super struct. His reasoning is that everything can be passed around at once if need be, and it will make it easier to track where everything is, rather than having a bunch of lose variable. His idea is for something like so:

struct{
int module_state;
M1_Data module_1_data;
int last_m1_command;
M2_Data module_2_data;
...
} SuperState;

static SuperState state

I am not sure I agree with his reasoning. What would the preferred way to handle this, and what are the upsides/downsides of both methods other than the ones listed?

Joe
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  • You should probably avoid having many global variables... (for readability reasons)... So having a somehow big `struct` is often better. But it is a matter of opinion. – Basile Starynkevitch Jun 17 '15 at 14:18
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    Any time I see variables numbered in this way, I wonder why an array, list or other data structure is not being used instead. – Robert Harvey Jun 17 '15 at 14:37
  • Each module has its own pieces of data that are of differing types, so it would not be possible to store them all in an array. Otherwise, I would probably agree. – Joe Jun 17 '15 at 14:39
  • possible duplicate of [Confusion of scope of a variable: Is Global Variable a solution?](http://programmers.stackexchange.com/questions/156410/confusion-of-scope-of-a-variable-is-global-variable-a-solution) – gnat Jun 17 '15 at 14:41
  • @gnat: Ehm, not really. – Robert Harvey Jun 17 '15 at 14:41
  • @RobertHarvey "the cleanest way to do this is to create a data structure which contains all the variables that you require, and pass a reference to this structure to all your functions" – gnat Jun 17 '15 at 14:42
  • @gnat: Look at the two titles. It has to be closer than that, and "your answer is over here" doesn't make a question a duplicate. – Robert Harvey Jun 17 '15 at 14:43

1 Answers1

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Personally, I would rather use structures, but not one common, I would use one for each module instead, with the properties I need to "publish" for other modules to be able to use.

Simple global variables are more difficult to maintain.

Using a structure per module will get rid of unnecessary dependencies (data related to a single module, and only to that module, is in the same place) between modules, and a structure is easy to pass all in once by pointer.

Dmitri Sologoubenko
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