*void allocating

[flegmik]

Hi, firstly I forgot to thank you in some thread about allocating the struct... So I thank everyone who helped me improve my code...
It will be very similiar right now, cause my program have to run under unix and I have some serious problems with my Putty right now... (should install some linux)

Point is all functions are valid, its just all about the while cycle... cause I am afraid of memory leaks

//void* SQLgetLineFromTable(&listOfTables->table); returns null if end of file

//void SQLinsertLineToTable(SQLtable* table,*void,t_size);

void* d_data= SQLgetLineFromTable(&listOfTables->table);        SQLtable* tabulka = SQLcreateTable();


        while (d_data!=NULL){
        SQLinsertLineToTable(tabulka,d_data,SQL_DATA_SIZE);
        d_data = SQLgetLineFromTable(&listOfTables->table);
        }

Should I allocate d_data and still reallocate them or its fine like this? Or is there any other way so I can controll end of file through SQLgetLineFromTable(&listOfTables->table); which returns null when reaches the EOF

[flegmik]

Havent found anything to edit my previous post

So I wanna allocate memory insade the structere, I wanna allocate it for SQLtable* table in SQLresult->data->table

Any Ideas how to allocate memory for struct in struct
Thanks

typedef struct {	SQLtypeOfResult type;
	union {
		int number;
		SQLtable* table;
	} data;
} SQLresult;
//i allocate memory for the struct
SQLresult* pResult = malloc (sizeof(SQLresult));
//this will allocate a memory just for table   
 SQLtable* tabulka = malloc (sizeof(SQLtable));

//this doesnt work cause data is anonymous
(pResult->data->table)* tabulka = malloc (sizeof(SQLtable));

//SQLtable is just another struct

[anduril462]

Havent found anything to edit my previous post

There's a 1 hour time limit on edits.

So I wanna allocate memory insade the structere, I wanna allocate it for SQLtable* table in SQLresult->data->table

Any Ideas how to allocate memory for struct in struct
Thanks

typedef struct {    SQLtypeOfResult type;
    union {
        int number;
        SQLtable* table;
    } data;
} SQLresult;
//i allocate memory for the struct
SQLresult* pResult = malloc (sizeof(SQLresult));
//this will allocate a memory just for table   
 SQLtable* tabulka = malloc (sizeof(SQLtable));

//this doesnt work cause data is anonymous
(pResult->data->table)* tabulka = malloc (sizeof(SQLtable));

//SQLtable is just another struct

Try

pResult = malloc(sizeof(*pResult));  // this is a little safer, if the type of pResult changes, this will still allocate the correct number of bytes
pResult->data.table = malloc(sizeof(*(pResult->data.table)));

[flegmik]

yeah thanks. i have one lame question... if I have buffer, lets say

 char* buffer = "this is my sentence";
           char* sth = buffer;
            *(sth+5) = '\0';
           free(buffer);

Is this correct? Would valgrind say no memory leaks? Thanks for the help above.

[anduril462]

Where did that come from? No, it's not a memory leak, but it's invalid. buffer points to a string constant. So does sth after line 2. You try to change the 5th char in that constant, but you can't because it's a constant. You need an array or malloc'ed memory for that to work. The call to free is also invalid. You have to give free an address that was returned from malloc. I think you should do some serious reading on structs, unions, pointers, strings and dynamic memory. We have a tutorial here (C, C++ Programming Tutorials - Cprogramming.com), and Google has lots more.