#calloc

calloc() 與 malloc() 的差異

前陣子在 Hacker News Daily 上看到的，原文是 2016 的文章：「Why does calloc exist?」，裡面講的東西包括了 implementation dependent 的項目，所以要注意一下他的結論未必適用於所有的平台與情境。 malloc() 與 calloc() 的用法是這樣，其中 calloc() 會申請 count 個 size 的空間： void* buffer1 = malloc(size); void* buffer2 = calloc(count, size); 第一個差異是，count * size 可能會 overflow (而 integer overflow 在 C 裡面是 undefined behavior)，這點除非你在乘法時有檢查，不然大多數的行為都還是會生一個值出來。 而 calloc() 則是會幫你檢查，當檢查會發生…

I realized I couldn't draw Minotaurs or "bara" characters that good. Whoops.

Happy Year of the Ox! (Or Cow or whatever bovine suits you fancy.)

I can now tackle a Crystal Story II character(s) which I've neglected to draw since Christmas 2019 even then they were drawn as Dargon Hybrids. (No one question what was Namina doing at that time.) Excuse me for making Koras speak in Norwegian. I made her wear a viking helmet because it'll make her look like an ox and wanted to make her speak in a Norwegian accent except I'm bad at it.

I really can't wait for Year of Dragon for obvious reasons. Plus I'm not sure what to do with Rabbit or Tiger.

Dynamic Memory Allocation:-

Every program allocates memory during the runtime and load time, but how much memory will be allocated during the runtime is called dynamic memory allocation.

If the size is decided during the compile time only that called static memory allocation.

Entire 4GB memory is split into two parts such as lower 3GB memory is called as user space and upper 1GB memory is called…

Nathaniel J. Smith on the purpose of calloc:

When the operating system hands out memory to a process, it always zeros it out first, because otherwise our process would be able to peek at whatever detritus was left in that memory by the last process to use it, which might include, like, crypto keys, or embarrassing fanfiction. So that’s the first way that calloc cheats: when you call malloc to allocate a large buffer, then probably the memory will come from the operating system and already be zeroed, so there’s no need to call memset. But you don’t know that for sure! Memory allocators are pretty inscrutable. So you have to call memset every time just in case. But calloc lives inside the memory allocator, so it knows whether the memory it’s returning is fresh from the operating system, and if it is then it skips calling memset. And this is why calloc has to be built into the standard library, and you can’t fake it yourself.