zeroing out memory

Question

gcc 4.4.4 C89

I am just wondering what most C programmers do when they want to zero out memory.

For example, I have a buffer of 1024 bytes. Sometimes I do this:<

Answer 1

When you define char buffer[1024] without initializing, you're going to get undefined data in it. For instance, Visual C++ in debug mode will initialize with 0xcd. In Release mode, it will simply allocate the memory and not care what happens to be in that block from previous use.

Also, your examples demonstrate runtime vs. compile time initialization. If your char buffer[1024] = { 0 } is a global or static declaration, it will be stored in the binary's data segment with its initialized data, thus increasing your binary size by about 1024 bytes (in this case). If the definition is in a function, it's stored on the stack and is allocated at runtime and not stored in the binary. If you provide an initializer in this case, the initializer is stored in the binary and an equivalent of a memcpy() is done to initialize buffer at runtime.

Hopefully, this helps you decide which method works best for you.