Weird bug using fopen() inside a function - c

Question

I've been looking around for like 4hours and cannot find where the problem is.
I got this function over here which is supposed to open a file.
In the function I successfully get into the != NULL condition thus returning 1, then in the main the value of my pointer test_file_1 is null (and then segfault when fclose)
I do not understand why because I am assigning the return value of fopen to my pointer !!
Here is the prototype :
/*
* Open a file and save its file pointer into file_to_load
* If it worked, returns 1
* Else, 0
*
* Prints its own error message, so you only have to use the return
* value to set the program behavior as wished
*
* filename : name of the file (+ path if needed)
* file_to_load : the file to be loaded
*
*/
int load_file(char* filename, FILE* file_to_load);
And here is the function by itself :
int load_file(char* filename, FILE* file_to_load)
{
//r is for read-only mode, we do not want to let the program edit the file
//We will only save when told (using save_file)
if( (file_to_load = fopen(filename, "r")) != NULL )
{
return 1;
}
else
{
fprintf(stderr, THE_FILE);
fprintf(stderr, filename);
fprintf(stderr, CANT_BE_OPENED);
// Should include the error number for convenience
return 0;
}
}
And .. here is the use in the main :
FILE* test_file_1 = NULL;
//Closed only if exists or else .. segfault
if ( (load_file("../bin/test", test_file_1)) == 1)
{
fclose(test_file_1);
}

Answer 1

C is pass-by-value, not pass-by-reference.
That means a function always gets a copy of its arguments, and changing its copy has no effect on the expression used on calling.
Use additional indirection, here the modified lines (each has exactly one * or & more):
int load_file(char* filename, FILE** file_to_load);
int load_file(char* filename, FILE** file_to_load)
if( (*file_to_load = fopen(filename, "r")) != NULL )
if ( (load_file("../bin/test", &test_file_1)) == 1)
BTW: It would be better to return the file as the return-value, unless you need the return-value for something else or there are other reasons not shown in the example.

Answer 2

Here is a simple program which pretty much does what you want.
int load_file(char *filename, FILE *file_to_load){
file_to_load = fopen(filename, "r");
if(file_to_load !=0)
return 1;
else
return 0;
}
int main(int argc, char *argv[]){
FILE file_to_load;
if(load_file(argv[1],&file_to_load) == 1)
printf("File exists\n");
else
printf("Error loading the given file\n");
}
I have taken the file as a command line argument and changed the error messages but you can alter it according to your requirements.