Convert C/C++ code to assembly language

We use g++ compiler to turn provided C code into assembly language. To see the assembly code generated by the C compiler, we can use the “-S” option on the command line:
Syntax:

$ gcc -S filename.c

This will cause gcc to run the compiler, generating an assembly file. Suppose we write a C code and store it in a file name “geeks.c” .

// C code stored in geeks.c file 
#include <stdio.h> 
  
// global string 
char s[] = "GeeksforGeeks"; 
  
// Driver Code 
int main() 
{ 
    // Declaring variables 
    int a = 2000, b =17; 
      
    // Printing statement 
    printf("%s %d \n", s, a+b); 
} 

Running the command:

$ gcc -S geeks.c

This will cause gcc to run the compiler, generating an assembly file geeks.s, and go no further. (Normally it would then invoke the assembler to generate an object- code file.)

The assembly-code file contains various declarations including the set of lines:

    .section    __TEXT, __text, regular, pure_instructions 
    .macosx_version_min 10, 12 
    .globl    _main 
    .align    4, 0x90 
_main:                                  ## @main 
    .cfi_startproc 
## BB#0: 
    pushq    %rbp 
Ltmp0: 
    .cfi_def_cfa_offset 16 
Ltmp1: 
    .cfi_offset %rbp, -16 
    movq    %rsp, %rbp 
Ltmp2: 
    .cfi_def_cfa_register %rbp 
    subq    $16, %rsp 
    leaq    L_.str(%rip), %rdi 
    leaq    _s(%rip), %rsi 
    movl    $2000, -4(%rbp)         ## imm = 0x7D0 
    movl    $17, -8(%rbp) 
    movl    -4(%rbp), %eax 
    addl    -8(%rbp), %eax 
    movl    %eax, %edx 
    movb    $0, %al 
    callq    _printf 
    xorl    %edx, %edx 
    movl    %eax, -12(%rbp)         ## 4-byte Spill 
    movl    %edx, %eax 
    addq    $16, %rsp 
    popq    %rbp 
    retq 
    .cfi_endproc 
  
    .section    __DATA, __data 
    .globl    _s                      ## @s 
_s: 
    .asciz    "GeeksforGeeks"
  
    .section    __TEXT, __cstring, cstring_literals 
L_.str:                                 ## @.str 
    .asciz    "%s %d \n"
  
  
.subsections_via_symbols 

Each indented line in the above code corresponds to a single machine instruction. For example, the pushq instruction indicates that the contents of register %rbp should be pushed onto the program stack. All information about local variable names or data types has been stripped away. We still see a reference to the global
variable s[]= “GeeksforGeeks”, since the compiler has not yet determined where in memory this variable will be stored.

This article is contributed by Sahil Rajput. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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