The main differences, aside from syntax and free vs. delete, are you can portably replace ::operator new; malloc comes with realloc, for which new has no equivalent; new has the concept of a new_handler, for which there is no malloc equivalent. (Replacing malloc opens up a can of worms. It can be done, but not … Read more
@fd – the RedHat bug had your answer. The mallinfo function has been deprecated, and won’t be updated. A true query stats API is TDB. Today, you have malloc_stats and malloc_info. I can’t find any documentation on either one, but here’s what they give you. Is this close enough to what you need? (gdb) call … Read more
The easiest way to do it is to keep a linked list of free block. In malloc, if the list is not empty, you search for a block large enough to satisfy the request and return it. If the list is empty or if no such block can be found, you call sbrk to allocate … Read more
If we change the program to see where the malloc‘d memory is: #include <unistd.h> #include <stdio.h> #include <stdlib.h> void program_break_test() { printf(“%10p\n”, sbrk(0)); char *bl = malloc(1024 * 1024); printf(“%10p\n”, sbrk(0)); printf(“malloc’d at: %10p\n”, bl); free(bl); printf(“%10p\n”, sbrk(0)); } int main(int argc, char **argv) { program_break_test(); return 0; } It’s perhaps a bit clearer that … Read more
No; you shouldn’t cast the result, since: It is unnecessary, as void * is automatically and safely promoted to any other pointer type in this case. It adds clutter to the code, casts are not very easy to read (especially if the pointer type is long). It makes you repeat yourself, which is generally bad. … Read more
It’s quite simple, as long as you pass to free() the same pointer returned by malloc() it’s fine. For example char *readInput(size_t size) { char *input; int chr; input = malloc(size + 1); if (input == NULL) return NULL; while ((i < size) && ((chr = getchar()) != ‘\n’) && (chr != EOF)) input[i++] = … Read more
The C language itself does not specify directly for a heap or how it should work, but does provide pointers, etc. malloc and its cousins are part of something called the C Standard Library, and are functions that you link to with any standard implementation of C, and those do provide access to memory that … Read more
You need to use dynamic memory when: You cannot determine the maximum amount of memory to use at compile time; You want to allocate a very large object; You want to build data structures (containers) without a fixed upper size; You don’t always know how much memory you will need to set aside at compile … Read more
My favorite: #include <stdlib.h> struct st *x = malloc(sizeof *x); Note that: x must be a pointer no cast is required include appropriate header
I’m out for a compelling reason. It depends on how you define “compelling”. Many of the arguments you have thus far rejected are certainly compelling to most C++ programmers, as your suggestion is not the standard way to allocate naked arrays in C++. The simple fact is this: yes, you absolutely can do things the … Read more