From http://www.gnu.org/s/libc/manual/html_node/Heap-Consistency-Checking.html#Heap-Consistency-Checking: Another possibility to check for and guard against bugs in the use of malloc, realloc and free is to set the environment variable MALLOC_CHECK_. When MALLOC_CHECK_ is set, a special (less efficient) implementation is used which is designed to be tolerant against simple errors, such as double calls of free with the same … Read more
It’s significant, especially as fragmentation grows and the allocator has to hunt harder across larger heaps for the contiguous regions you request. Most performance-sensitive applications typically write their own fixed-size block allocators (eg, they ask the OS for memory 16MB at a time and then parcel it out in fixed blocks of 4kb, 16kb, etc) … Read more
Actually, malloc() (and other C runtime heap functions) are module dependant, which means that if you call malloc() in code from one module (i.e. a DLL), then you should call free() within code of the same module or you could suffer some pretty bad heap corruption (and this has been well documented). Using HeapAlloc() with … Read more
Simple answer : free(testPerson) is enough . Remember you can use free() only when you have allocated memory using malloc, calloc or realloc. In your case you have only malloced memory for testPerson so freeing that is sufficient. If you have used char * firstname , *last surName then in that case to store name … Read more
For good reasons, virtually no memory allocator returns blocks to the OS Memory can only be removed from your program in units of pages, and even that is unlikely to be observed. calloc(3) and malloc(3) do interact with the kernel to get memory, if necessary. But very, very few implementations of free(3) ever return memory … Read more
Ironically enough, the Adobe Source Libraries has a adobe::capture_allocator class that was written specifically with this kind of DLL safety in mind. The way it works is to capture the local new and delete at this point it is instantiated, and to carry them both around for the lifetime of the object. (See adobe::new_delete_t for … Read more
You don’t use malloc for that. Why would you anyway, in a C++ program? You also don’t use new for executable memory, however. There’s the Windows-specific VirtualAlloc function to reserve memory which you then mark as executable with the VirtualProtect function applying, for instance, the PAGE_EXECUTE_READ flag. When you have done that, you can cast … Read more
Any modern operating system will clean up everything after a process terminates, but it’s generally not a good practice to rely on this. It depends on the program you are writing. If it’s just a command line tool that runs and terminates quickly, you may not bother cleaning up. But be aware that it is … Read more
What is keeping me from writing into the memory location beyond 81 units? Nothing. However, doing this results in undefined behaviour. This means anything can happen, and you shouldn’t depend on it doing the same thing twice. 99.999% of the time this is a bug. What can I do to prevent that? Always check that … Read more
First, copying into an array that is too small: C has no protection for going past array bounds, so if there is nothing sensitive at dst1[5..9], then you get lucky, and the copy goes into memory that you don’t rightfully own, but it doesn’t crash either. However, that memory is not safe, because it has … Read more