Sporadic C errors apear

Question

I'm new to programming in C and am mainly playing around with it (I normally work in Java) so please excuse my ignorance if this is an obvious error... I've just started making a simple text based Space Sim and I get two different strange errors that will sporadically appear every 2-3 runs that I'm struggling to decipher (only 1 appears at a time). I'm assuming that I have allocated a variable incorrectly, but I could do with some help having it pointed out.

The code is split into 3 files:

Physics.c:

typedef enum { false, true } bool; //define what a boolean is

//define a vector
typedef struct {
    int x;
    int y;
} Vector; 

bool compareVectors(Vector vectorA, Vector vectorB){
    if ((vectorA.x == vectorB.x) && (vectorA.y == vectorB.y)){
        return true;
    } else {
        return false;
    }
}

Space.c:

#include 
#include 
#include "Physics.c" //includes space

enum Type {
    craft = 0,
    planet,
    star
};


typedef struct {
    enum Type type;
    Vector position;
} Object;

typedef struct {
    Object *array;
    int used;
    int size;

} Space;


void initSpace(Space *a, int initialSize) {
    a->array = (Object *)malloc(initialSize * sizeof(int));
    a->used = 0;
    a->size = initialSize;
}

//inserts a new object in space and returns the location of the new object in the array
int insertToSpace(Space *a, Object element) {
    if (a->used == a->size) {
        a->size *= 2;
        a->array = (Object *)realloc(a->array, a->size * sizeof(int));
    }
    a->array[a->used++] = element;

    return a->used - 1;
}

void freeSpaceArray(Space *a) {
    free(a->array);
    a->array = NULL;
    a->used = a->size = 0;
}

//creates a new object in space and returns the location of the object in the array
int createObjectInSpace(Space *a, int type, int xPos, int yPos){
    Object newObject;
    Vector tempVector;

    newObject.type = type;
    tempVector.x = xPos;
    tempVector.y = yPos;
    newObject.position = tempVector;

    return insertToSpace(a, newObject);
}

//returns the number of objects at that location in space based on Vector location
int objectsAtLocationVector(Space *a, Vector pos){
    int count = 0;
    for (int i = 0; i < a->used; i++){
        if (compareVectors(a->array[i].position, pos)){
            count++;
        }
    }
    return count;
}

//returns the number of objects at that location in space, based on an x/y int location
int objectsAtLocationInt(Space *a, int xPos, int yPos){
    Vector tempVector;
    tempVector.x = xPos;
    tempVector.y = yPos;
    return objectsAtLocationVector(a, tempVector);
}

//returns a list of all objects at the specified location vector
Space getObjectsAtLocationVector(Space *space, Vector pos){
    Space newSpace;
    int noOfObjects = objectsAtLocationVector(space, pos);

    initSpace(&newSpace, noOfObjects);

    if (noOfObjects > 0){
        for (int i = 0; i < space->used; i++){
            if (compareVectors(space->array[i].position, pos)){
                insertToSpace(&newSpace, space->array[i]);
            }
        }
    } 

    return newSpace;
}
//returns a list of all objects at the specified integer location
Space getObjectsAtLocationInt(Space *space, int xPos, int yPos){
    Vector tempVector;
    tempVector.x = xPos;
    tempVector.y = yPos;
    return getObjectsAtLocationVector(space, tempVector);
}

Main (Space_In_C.c):

#include 
#include "Space.c" //includes space

//Setup the main variables
void setup(Vector *myShip, Space *space){
    myShip -> x = 0;
    myShip -> y = 0;

    initSpace(space, 10); //initialise the space array

    return;
}

int main(int argc, char *argv[]) {
    Vector myShip; //create the Vector that stores the ships location
    Space space; //create the Space array

    setup(&myShip, &space); //set up all key variables

    createObjectInSpace(&space, planet, 7, 5);  
    createObjectInSpace(&space, craft, 7, 5);

    Space objects = getObjectsAtLocationInt(&space, 7, 5);

    printf("%d", objects.array[1].type);

    return 0;
}

And here is the first error:

Terminated due to signal: SEGMENTATION FAULT (11)
0  lli                      0x000000010705dda9 void std::__1::seed_seq::generate(unsigned int*, unsigned int*) + 9993
1  lli                      0x000000010705e83b void std::__1::seed_seq::generate(unsigned int*, unsigned int*) + 12699
2  libsystem_platform.dylib 0x00007fffbd52fbba _sigtramp + 26
3  libsystem_platform.dylib 0x00007fff59489ce0 _sigtramp + 2616566080
4  lli                      0x0000000106f303fe llvm::raw_ostream& llvm::operator<<(llvm::raw_ostream&, llvm::DomTreeNodeBase const*) + 12270
5  lli                      0x0000000106fe21f6 llvm::SmallVectorImpl > >::operator=(llvm::SmallVectorImpl > >&&) + 4038
6  lli                      0x0000000106d2376f std::__1::__tree, std::__1::__map_value_compare, std::__1::less, true>, std::__1::allocator > >::destroy(std::__1::__tree_node, void*>*) + 23615
7  lli                      0x0000000106d20b4e std::__1::__tree, std::__1::__map_value_compare, std::__1::less, true>, std::__1::allocator > >::destroy(std::__1::__tree_node, void*>*) + 12318
8  lli                      0x0000000106d20c9e std::__1::__tree, std::__1::__map_value_compare, std::__1::less, true>, std::__1::allocator > >::destroy(std::__1::__tree_node, void*>*) + 12654
9  lli                      0x0000000106788426 void std::__1::vector >::__push_back_slow_path(unsigned long long&&) + 24694
10 libsystem_c.dylib        0x00007fffbd3b717f __cxa_finalize_ranges + 339
11 libsystem_c.dylib        0x00007fffbd3b74b2 exit + 55
12 lli                      0x0000000106d22d56 std::__1::__tree, std::__1::__map_value_compare, std::__1::less, true>, std::__1::allocator > >::destroy(std::__1::__tree_node, void*>*) + 21030
13 lli                      0x0000000106788290 void std::__1::vector >::__push_back_slow_path(unsigned long long&&) + 24288
14 libdyld.dylib            0x00007fffbd322255 start + 1
15 libdyld.dylib            0x0000000000000002 start + 1120787886
Stack dump:
0.  Program arguments: lli /var/folders/9k/f9_xm4857vq6_fysth4wl5mh0000gn/T/com.coderunnerapp.CodeRunner/CodeRunner/clang/Space_In_C.ll

And the second error:

Terminated due to signal: ABORT TRAP (6)
    lli(5537,0x7fffc60423c0) malloc: *** error for object 0x7ff8e8603fc0: incorrect checksum for freed object - object was probably modified after being freed.
    *** set a breakpoint in malloc_error_break to debug
    00  lli                      0x0000000107f84da9 void std::__1::seed_seq::generate(unsigned int*, unsigned int*) + 9993
    1  lli                      0x0000000107f8583b void std::__1::seed_seq::generate(unsigned int*, unsigned int*) + 12699
    2  libsystem_platform.dylib 0x00007fffbd52fbba _sigtramp + 26
    3  libsystem_platform.dylib 0x00000001109c10d0 _sigtramp + 1397298480
    4  libsystem_c.dylib        0x00007fffbd3b6420 abort + 129
    5  libsystem_malloc.dylib   0x00007fffbd4b0fb1 szone_error + 626
    6  libsystem_malloc.dylib   0x00007fffbd4a6fbf tiny_free_list_remove_ptr + 292
    7  libsystem_malloc.dylib   0x00007fffbd4bb932 tiny_free_no_lock + 1484
    8  libsystem_malloc.dylib   0x00007fffbd4bc0f3 free_tiny + 671
    9  lli                      0x0000000107c4ca82 void std::__1::vector >::__push_back_slow_path(llvm::JITEventListener* const&&&) + 7122
    10 lli                      0x00000001076af1c5 void std::__1::vector >::__push_back_slow_path(unsigned long long&&) + 24085
    11 libdyld.dylib            0x00007fffbd322255 start + 1
    12 libdyld.dylib            0x0000000000000002 start + 1120787886
    Stack dump:
    0.  Program arguments: lli /var/folders/9k/f9_xm4857vq6_fysth4wl5mh0000gn/T/com.coderunnerapp.CodeRunner/CodeRunner/clang/Space_In_C.ll

Apologies for the massive code dump! Any help would be much appreciated!

Geoff S · Accepted Answer

In initSpace, it looks like you are wanting to allocate memory for an array of Objects (which contain an enum and a Vector), but you are only allocating enough memory for an array of int's

  a->array = (Object *)malloc(initialSize * sizeof(int));

should be

  a->array = (Object *)malloc(initialSize * sizeof(Object));

There may well be other bugs, but that one stood out.

Sporadic C errors apear

Answers (1)

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