Agfdhyk

i begginer at c programing and while i am runing my C program i got strange error:

 Program received signal SIGSEGV, Segmentation fault.

0x0000559625ce4a56 in inputNewCountry (cordinateOfCountry=...) at /home/david/CLionProjects/untitled/Countries.c:40

40    newCountry->cordinateOfCountry.xLeft=cordinateOfCountry.xLeft;



Program terminated with signal SIGSEGV, Segmentation fault.

The program no longer exists.

the code of my function:

Country* inputNewCountry(cordinate cordinateOfCountry)

{

  Country *newCountry;

  newCountry->cordinateOfCountry.xLeft=cordinateOfCountry.xLeft;

    newCountry->cordinateOfCountry.xRight=cordinateOfCountry.xRight;

  newCountry->cordinateOfCountry.yLeft=cordinateOfCountry.yLeft;

    newCountry->cordinateOfCountry.yRight=cordinateOfCountry.yRight;

  newCountry->cities=NULL;

  newCountry->numberOfCities=0;

  return newCountry;

}

"struch cordinate":

typedef struct cordinate

{

    int xLeft,yLeft;

    int xRight,yRight;

}cordinate;

i dont have any idea what i am doing wrong, can someone please help?

Country *newCountry;

here you define an uninitialized pointer variable.

newCountry->cordinateOfCountry.xLeft=[...]

here (in the next line) you write data to an offset (calculated by cordinateOfCountry.xLeft) to this uninitialized pointer variable, a.k.a. you are writing data to a random point in memory.

You should allocate memory for newCountry, for example with the stdlib.h function malloc:

Country *newCountry = malloc(sizeof(Country));

Remember to free any allocated memory this way.

You could also allocate a global variable (but be careful since then calling the function more than once will overwrite the data):

Country globalCountry;



Country inputNewCountry(cordinate cordinateOfCountry)

{

    Country *newCountry = &globalCountry;

    [...]

You can hide the global variable to only be visible inside of the function:

Country inputNewCountry(cordinate cordinateOfCountry)

{

    static Country hiddenGlobalCountry; // Other functions cannot see hiddenGlobalCountry, but it still acts like a global variable

    // Note that just Country hiddenGlobalCountry won't work, since such a variable will be destroyed once the function exits (making it little better than writing to uninitialized memory)

    Country *newCountry = &hiddenGlobalCountry;

    [...]

Or you could simply return a Country instead:

Country inputNewCountry(cordinate cordinateOfCountry)

{

  Country newCountry;

  newCountry.cordinateOfCountry.xLeft=cordinateOfCountry.xLeft;

  newCountry.cordinateOfCountry.xRight=cordinateOfCountry.xRight;

  newCountry.cordinateOfCountry.yLeft=cordinateOfCountry.yLeft;

  newCountry.cordinateOfCountry.yRight=cordinateOfCountry.yRight;

  newCountry.cities=NULL;

  newCountry.numberOfCities=0;

  return newCountry;

}