typedef and malloc error in c(unknown srtuct type)

Question

I have a following typedef in my C program which throws an error.This is part of my code-

typedef struct Room
{
    int ** values;
}Room;

int createRoom(Room pm) // it give me error unknown type Room
{
    //some code here
}

int main()
{
    Room *pm;
    pm=(Room)malloc(sizeof(Room));
    int n=callfun(pm);
    return 0;
}

It gives me unknown type Room error. Also, I get an error in the malloc line. Can anyone tell me where I am wrong

Please copy and paste your exact code; what you have posted would not give "unknown type Room" . — M.M, Feb 17 '15 at 04:47
I fixed that error of `unknown type room`.Now I am getting this error- `incompatible implicit declaration of built-in function malloc` — , Feb 17 '15 at 04:52

score 0 · Answer 1 · answered Feb 17 '15 at 04:46

0

 pm=(Room)malloc(sizeof(Room));

Should be,

 pm=(Room*)malloc(sizeof(Room));

pm is Room*.

As stated in comment, as malloc return void * you need not to cast it, so it can be,

pm=malloc(sizeof(Room));

answered Feb 17 '15 at 04:46

Pranit Kothari

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struct tags are a separate "space" to typenames in C – M.M Feb 17 '15 at 04:48
Separate space? You mean to say, name and variable of struct can be same? – Pranit Kothari Feb 17 '15 at 04:50
The struct tag (the name just after `struct`) does not interfere with anything else – M.M Feb 17 '15 at 04:50

score 0 · Accepted Answer · edited May 23 '17 at 11:50

0

pm=(Room)malloc(sizeof(Room));

should be

pm=(Room *)malloc(sizeof(Room));

Don't cast malloc()

Just do

pm= malloc(sizeof(Room));

edited May 23 '17 at 11:50

Community

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1

answered Feb 17 '15 at 04:46

Gopi

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I fixed that error of `unknown type room`.Now I am getting this error- `incompatible implicit declaration of built-in function malloc` – Feb 17 '15 at 04:51
@Coder `#include` – Gopi Feb 17 '15 at 05:14

typedef and malloc error in c(unknown srtuct type)

2 Answers2