No need to cast return value of malloc as its return type is void*. Can someone explain why do some programmers use (char *) in front of the malloc? They are doing wrong (most probably) by casting it (in good programmers opinion). As wiki says: malloc returns a void pointer (void *), which indicates that … Read more
When an object is “double-freed”, the most common cause is that you’re (unnecessarily) releasing an autoreleased object, and it is later autoreleased when the containing autorelease pool is emptied. I’ve found that the best way to track down the extra release is to use the NSZombieEnabled environment variable for the affected executable in Xcode. For … Read more
Linux does deferred page allocation, aka. ‘optimistic memory allocation’. The memory you get back from malloc is not backed by anything and when you touch it you may actually get an OOM condition (if there is no swap space for the page you request), in which case a process is unceremoniously terminated. See for example … Read more
You want to modify the value of an int* (your array) so need to pass a pointer to it into your increase function: void increase(int** data) { *data = realloc(*data, 5 * sizeof int); } Calling code would then look like: int *data = malloc(4 * sizeof *data); /* do stuff with data */ increase(&data); … Read more
The following worked for me. Not sure whether there is a better way. Install libc6-dbg (which you have already done): sudo apt-get install libc6-dbg Install the eglibc-source package (ubuntu actually uses eglibc): sudo apt-get install eglibc-source. Unpack the tar file that was installed in /usr/src/glibc: /usr/src/glibc $ sudo tar xvf eglibc-2.19.tar.xz Crank up gdb and … Read more
You likely forgot to #include <stdlib.h>
You need to change if((*matrix[i] = (int*)malloc(col * sizeof(int))) == NULL) to if(((*matrix)[i] = (int*)malloc(col * sizeof(int))) == NULL) // ^ ^ You need to dereference matrix before using the array subscript. *matrix[i] is equivalent to *(matrix[i])
It’s not standard but if your library has a msize() function that will give you the size. A common solution is to wrap malloc with your own function that logs each request along with the size and resulting memory range, in the release build you can switch back to the ‘real’ malloc.
Never use pointer-to-pointer to allocate multi-dimensional arrays. It is wide-spread but bad and incorrect practice. Doing so will not give you a true 2D array, and it will lead to slower code because of heap fragmentation. It also makes the code harder to write, read and maintain, which in turn increases the potential for memory … Read more
No they’re not absolutely the same. While both let you store the same number and type of objects, keep in mind that: You can free() a malloced array, but you can’t free() a variable length array (although it goes out of scope and ceases to exist once the enclosing block is left). In technical jargon, … Read more