#Memory-layout-of-variable-in-C-program
- As you know, variable in C can be classified info local variable, global variable. Local variable is stored in Stack, memory allocated with malloc/alloc locates in Heap. Global variable and Static Variable is located in global data area, which consists of DS and BSS. DS (data segment) contains initialized variable, which is not zero. DS can be divided into readonly DS area and read write DS area. BSS (block started by symbol) contains uninitialized variable or variable initialized with zero, which can also be divied into readonly BSS area and read write area.
2.Sample
void ppp(int parameter) {
return;
}
int main() {
ppp(12);
return 0;
}
REG BEGIN PUSH EBP MOV EBP, ESP
EBP 0036FD88 0036FD88 0036FD74 main in
ESP 0036FD78 0036FD74 0036FD74
REG BEGIN PUSH EBP MOV EBP, ESP
EBP 0036FD74 0036FD74 0036FC9C ppp in
ESP 0036FCA0 0036FC9C 0036FC9C
REG BEGIN MOV ESP, EBP POP EBP
EBP 0036FC9C 0036FC9C 0036FD74 ppp return
ESP 0036F9D0 0036FC9C 0036FCA0
REG BEGIN MOV ESP, EBP POP EBP
EBP 0036FD74 0036FD74 0036FD88 main return
ESP 0036FD74 0036FD74 0036FD78
Before the program enter main procudure, EBP is 0x0036FD88, so this is the Base Address of current Call Frame, ESP is bigger than EBP, I think all of us can undersand this in X86 Cpu architecture. Now, we enter main, I think I should save the Base Address, right now. As we know, Context should be saved and recovered when key operations begins and stops. So 0x0036FD88 is save to stack, then ESP is decreased to 0x0036FD74. And the same time, EBP is decreased to ESP (0x0036FD84).