We have an issue with this code
struct foo { int NumberOfPointers; char *Pointers[1]; } xx; // Allocate A Block Of Pool With Room For 100 Pointers myHunkyStuff = malloc( sizeof(long) + 100 * sizeof (char *) );
Can anyone explain?
The H Matherson Crew
What is the problem, exactly? To get good answers you need to ask good questions, and you haven't even specified if this is a compiler problem (i.e does the compiler give you errors?) or a runtime problem (i.e, the code doesn't do what you want).
That said, your code doesn't make much sense. I'm guessing that you want to have one copy of the struct, and then allocate memory for 100 pointers to char, which is then to be assigned to the member Pointers of said struct. Instead, you're allocating memory for 100 pointers to char and one long.
Please describe what it is you want to achieve, and then you might get some sensible help.
Regards -Øyvind
What we're trying to do is new the object whats got the number of objects and the array just like C++. It compiles great. But when we run it we get errors. For some strange unexplicable reason the last pointer is not always kept on and we dont know why.
If you wanted to make sure you really did get the memory you needed you should to a slight over-allocation - don't try to figure out the size of the other elements in the struct and their offsets etc. Allocate sizeof(struct) + x*sizeof(ptr). Then you do know that you have got a pointer to a block large enough, without having involved any tricks.
Apart for an obvious error/typo in the code, the task itself is straightforward:
struct foo { int NumberOfPointers; char *Pointers[1]; } xx; // Allocate A Block Of Pool With Room For 100 Pointers myHunkyStuff = malloc( sizeof(xx) + (100-1)*sizeof (char *) );
You want the size of the overall structure (along with any padding that might be present between NumOfPointers and Pointers) plus an array of the 'extra to the one already in' the structure.