Passing a non dynamic 2 dimensional array into a function in C?

Question

How do you pass two dimensional arrays into a function?
When I pass it, it shows up in the visual studio debugger as a single dimensional array. The problem was that when I index sel_col[i], it gets the next character, instead of the next word.

Here is my function prototype:

void print_row(char sel_col[MAX_IDENT_LEN][MAX_IDENT_LEN]);

And here is the definition of my 2d array, and where I call it:

char sel_col[MAX_NUM_COL][MAX_IDENT_LEN];
print_row(sel_col);

Solution 1: Remove the first size identifier. Didn't work.

void print_row(char sel_col[][MAX_IDENT_LEN]);

Solution 2: Pass it by reference into the function. Didn't work.

    print_row(&sel_col);

Solution 3: Use double pointers. I don't want to go this route, since I would rewrite most of my code.

Un-tagged C++ as this question is in C.

Puppy
– Puppy

2011-05-01 06:17:11 +00:00
Commented May 1, 2011 at 6:17 — Puppy
– Puppy, Commented May 1, 2011 at 6:17

Seth Carnegie · Accepted Answer · 2011-05-01 04:27:30Z

1

In C, two-dimensional arrays look like one dimensional arrays; a char[3][3] is really a single-dimension array just 9 elements long, and the compiler performs some math to turn two smaller indices into one bigger one. Your function prototype looks correct. What was the problem? Were you getting a compiler error?

answered May 1, 2011 at 4:27

Seth Carnegie

75.3k22 gold badges185 silver badges252 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

chustar Over a year ago

The problem was that when I index sel_col[i], it gets the next character, instead of the next word.

Seth Carnegie Over a year ago

You can either try a char* array[SIZE] or show us the definition of the array you're passing.

Seth Carnegie Over a year ago

@chustar This small program works for me: codepad.org/gdcd1WKR It prints abc def ghi... on seperate lines, like you'd think it would.

chustar Over a year ago

I feel stupid now. I forgot to check the size of the array for situations where the passed array is less than my theoretical max.

Seth Carnegie Over a year ago

@chustar Yeah, usually almost any time you pass an array to a function, a rule of thumb is that if you don't see the length of the array being passed to that function also, something's probably wrong. There are notable exceptions though, such as most char*s of course, but you get the idea.

Collectives™ on Stack Overflow

Passing a non dynamic 2 dimensional array into a function in C?

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related