On Sun, 19 Dec 2004 12:32:12 +1100, Sam Watkins <[EMAIL PROTECTED]> wrote: > The heap can get much bigger, you can malloc as much as you want on the heap > (up to the limits of VM and process address space) and it won't segfault, e.g. > > char *c = malloc(100*1024*1024); > int i; > for (i=0; i<size; ++i) > c[i] = 'x'; > free(c);
That "up to the limits of..." is important, and the code above isn't safe. You should always check the output of *alloc to make sure it's non-NULL. Otherwise you're back in the crap-shoot of allocating statically and hoping there was enough space on the stack. > C++ allocates data on the heap when you use "new", and the STL containers > allocate their elements on the heap. For example these are ok: > > char *c = new char[100*1024*1024]; > // ... > delete[] c; Ditto here, though it should throw an exception if the memory couldn't be allocated. Older implementations will likely return 0. Incidentally, with C++ I tend to use vectors for a lot of arrays (you can reserve() space for a certain number of items so that it won't have to re-allocate) unless they're sparse, in which case I use maps. Appropriate try/catch blocks can then make sure that you're handling funny memory conditions correctly. In both cases you get to use the same operator[] notation as for arrays, but an invalid (non-negative) index will attempt to allocate the space you need. -- Michael A. Marsh http://www.umiacs.umd.edu/~mmarsh -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
