Simple logic: If you do not park in a legal parking space, nothing might happen but occasionally your car might get towed and you might get stuck with a huge fine. And, sometimes, as you try to find your way to the pound where your car was towed, you might get run over by a … Read more
On Windows 7 you will always get the low-fragmentation heap allocator, without explicitly calling HeapSetInformation() to ask for it. That allocator sacrifices virtual memory space to reduce fragmentation. Your program is not actually using 170 megabytes, you are just seeing a bunch of free blocks lying around, waiting for an allocation of a similar size. … Read more
To find the source of the problem, in Xcode go to Product > Scheme > Edit Scheme, and under Diagnostics tab enable all the Malloc settings and Guard Malloc. With that, run your application again, and Xcode will stop at the line causing the problem.
You have to free() the allocated memory in exact reverse order of how it was allocated using malloc(). Note that You should free the memory only after you are done with your usage of the allocated pointers. memory allocation for 1D arrays: buffer = malloc(num_items*sizeof(double)); memory deallocation for 1D arrays: free(buffer); memory allocation for 2D … Read more
I’ve used tcmalloc and read about Hoard. Both have similar implementations and both achieve roughly linear performance scaling with respect to the number of threads/CPUs (according to the graphs on their respective sites). So: if performance is really that incredibly crucial, then do performance/load testing. Otherwise, just roll a dice and pick one of the … Read more
It is undefined behaviour, so it is an error to deference freed pointer as strange things may (and will) happen. free() doesn’t change the value of the pointer so it keeps pointing to the heap in the process address space – that’s why you don’t get segfault, however it is not specified and in theory … Read more
The pointer is a pointer, and not an array. It can never be “recognized as an array”, because it is not an array. It is entirely up to you to remember the size of the array. For example: struct i_must_remember_the_size { size_t len; int * arr; }; struct i_must_remember_the_size a = { 10, NULL }; … Read more
“Why is this allowed to happen?” (write outside of bounds) C does not require the additional CPU instructions that would typically be needed to prevent this out-of-range access. That is the speed of C – it trusts the programmer, giving the coder all the rope needed to perform the task – including enough rope to … Read more
It is legal now, and retroactively since C++98! Indeed the C++ specification wording till C++20 was defining an object as (e.g. C++17 wording, [intro.object]): The constructs in a C++ program create, destroy, refer to, access, and manipulate objects. An object is created by a definition (6.1), by a new-expression (8.5.2.4), when implicitly changing the active … Read more
For GNU glibc: SYNOPSIS #include <malloc.h> size_t malloc_usable_size (void *ptr); DESCRIPTION The malloc_usable_size() function returns the number of usable bytes in the block pointed to by ptr, a pointer to a block of memory allocated by malloc(3) or a related function.