How do I compile the asm generated by GCC

Question

I m playing around with some asm code  and something is bothering me   I compile this    include  lt stdio h gt   int main int argc  char   argv     printf  Hello World n      return 0      with gcc file c -S -o file S this generates a nice little piece of asm code        cstring LC0       ascii  Hello World 0       text  globl  main  main  LFB3      pushq    rbp LCFI0      movq     rsp   rbp LCFI1      subq     16   rsp LCFI2      movl     edi  -4  rbp      movq     rsi  -16  rbp      leaq    LC0  rip    rdi     call     puts     movl     0   eax     leave     ret LFE3       section   TEXT   eh frame coalesced no toc strip static syms live support EH frame1       set L set 0 LECIE1-LSCIE1      long L set 0 LSCIE1       long   0x0      byte   0x1      ascii  zR 0       byte   0x1      byte   0x78      byte   0x10      byte   0x1      byte   0x10      byte   0xc      byte   0x7      byte   0x8      byte   0x90      byte   0x1      align 3 LECIE1   globl  main eh  main eh  LSFDE1       set L set 1 LEFDE1-LASFDE1      long L set 1 LASFDE1       long   LASFDE1-EH frame1      quad   LFB3-       set L set 2 LFE3-LFB3      quad L set 2      byte   0x0      byte   0x4      set L set 3 LCFI0-LFB3      long L set 3      byte   0xe      byte   0x10      byte   0x86      byte   0x2      byte   0x4      set L set 4 LCFI1-LCFI0      long L set 4      byte   0xd      byte   0x6      align 3 LEFDE1       subsections via symbols   My next problem is really  how do I compile this output  and can I make GCC do it for me

User · Answer

gcc can use an assembly file as input  and invoke the assembler as needed  There is a subtlety  though    If the file name ends with   s   lowercase  s    then gcc calls the assembler  If the file name ends with   S   uppercase  S    then gcc applies the C preprocessor on the source file  i e  it recognizes directives such as  if and replaces macros   and then calls the assembler on the result    So  on a general basis  you want to do things like this   gcc -S file c -o file s gcc -c file s

User · Answer

Yes  You can use gcc to compile your asm code  Use -c for compilation like this   gcc -c file S -o file o   This will give object code file named file o   To invoke linker perform following after above command   gcc file o -o file

User · Answer

If you have main s file  you can generate object file by GCC and also as    gcc -c main s   as main s -o main o   check this link  it will help you learn some binutils of GCC http   www thegeekstuff com 2017 01 gnu-binutils-commands

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You can embed the assembly code in a normal C program  Here s a good introduction  Using the appropriate syntax  you can also tell GCC you want to interact with variables declared in C  The program below instructs gcc that    eax shall be foo  ebx shall be bar the value in eax shall be stored in foo after the assembly code executed    n  int main void            int foo   10  bar   15            asm     volatile    addl    ebx   eax                                  a  foo                                 a  foo    b  bar                                          printf  foo bar  d n   foo           return 0

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You can use GAS  which is gcc s backend assembler   http   linux die net man 1 as

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Yes  gcc can also compile assembly source code  Alternatively  you can invoke as  which is the assembler   gcc is just a  driver  program that uses heuristics to call C compiler  C   compiler  assembler  linker  etc

User · Answer

nasm -f bin -o 2 hello 2 hello asm

[c] How do I compile the asm generated by GCC?

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