variables

variables

[RCS]

Hi all, 

  Can anyone explain me how global and local variables from C are treated in 
assembler? 
  Is that write that local variables are storage in the stack? 

  Thanks, 

                                     RCS. 

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Re: variables

[RCS]

Thanks, with that command-line I could anderestand 
a simple program as followed: 

C-CODE 
------ 

int a = 1; 

int main(void) 
{ 
  int b = 2; 

  a = b; 
} 

ASSEMBLER CODE 
-------------- 

	.file	"Variaveis.c" 
	.version	"01.01" 
gcc2_compiled.: 
globl a 
data 
	.align 4 
	.type	 a,@object 
	.size	 a,4		;  Global Variable Size Definition a (4 bytes) 
a: 
	.long 1			;  Global Variable a = 1 
text 
	.align 4 
globl main 
	.type	 main,@function 
main: 
	pushl %ebp 
	movl %esp,%ebp 
	subl $24,%esp 
	movl $2,-4(%ebp)	;  Local Variable b = 2 
	movl -4(%ebp),%eax 
	movl %eax,a		;  a = b 
L2: 
	leave 
	ret 
Lfe1: 
	.size	 main,.Lfe1-main 
	.ident	"GCC: (GNU) 2.95.3 20010315 (release) (conectiva)" 


ARE THE COMMENTS CORRECT ? 



Em Aug 2002, Dmitry Trunikov escreveu: 

>RCS wrote: 
> 
>> Can anyone explain me how global and local variables from C are treated 
>in 
>>assembler? 
>> Is that write that local variables are storage in the stack? 
>> 
>Yes. 
>You can compile c-program to asm-source. Try gcc -S program.c 
> 
>---------- 

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Re: variables

[Maciej Hrebien]

RCS wrote:
> 
> Hi all,
> 
>   Can anyone explain me how global and local variables from C are treated in
> assembler?
>   Is that write that local variables are storage in the stack?

Global variables are likely to be placed in data segment and all local -
pushed on the stack. But i think it really depends on C compiler how it
handles all Your data. If the program is tiny, a C compiler may all Your
data push on the stack - i don't know that C standard says that all Your
global data must be placed in data segment (i suppose it doesn't say)
but it seems that it works in that way for most of programs (not
hello-like).

-- 
Maciej Hrebien