Why gcc disassembler allocating extra space for local variable?

Question

I have written simple function in C,

void GetInput()
{
    char buffer[8];
    gets(buffer);
    puts(buffer);
}

When I disassemble it in g

Answer 1

Two things:

1. The compiler may reserve space for intermediate expressions to which you did not give names in the source code (or conversely not allocate space for local variables that can live entirely in registers). The list of stack slots in the binary does not have to match the list of local variables in the source code.
2. On some platforms, the compiler has to keep the stack pointer aligned. For the particular example in your question, it is likely that the compiler is striving to keep the stack pointer aligned to a boundary of 16 bytes.

Regarding your other question that you should have asked separately, xor %gs:0x14,%eax is clearly part of a stack protection mechanism, enabled by default. If you are using GCC, turn it off with -fno-stack-protector.