Local variables and addition not shown in Ghidra

Question

I am having some troubles with my learning of Assembly and reverse engineering. Specifically, I am learning about Global vs Local variables. For Global variables I have managed to get insights in assembly that they are stored in memory address. For Local variables I expect them to be stored on stack (theory), but my simple C code below, when being disassembled in Ghidra, does not show anything in main function.

C CODE:

void main()
{
    int x = 1;
    int y = 2;
    x = x + y;
}

GHIDRA OUTPUT:

Why can't I see anything in my Ghidra? It looks like an empty function to me, but clearly there should be some local variable declaration and then addition performed afterwards.

I really apologize for opening threads here often, but this is the only source where I can get help for such things. On Reddit they do not allow posting questions and referred me here.

EDIT - 25.09.2019:

As per suggestion I have added some code to my existing C Code to see if it will show up now in Assembly:

#include <stdio.h>

void main()
{
    int x = 1;
    int y = 2;

    x = x + y;

    printf("Rezultat = %d\n", x);

}

For this I had to set entry point back to CRT initialize, otherwise I could not use stdio Library. This is now the result of main function in Ghidra:

Now I am able to see the PUSH instruction and the value 0x03. This is probably the resulting value of addition 1 + 2, but I again can't nowhere see where are the local variables initialized nor where the arithmetic operation is performed.

Answer 1

you may either need to use the local variables or compile with optimizations disabled

I assume you are using msvc on windows ?? shown below is a snippet that was compiled on x64 for x64 in win 10 where you can clearly see the local vars being initialized and used

f:\git\usr\bin\ls -lg
total 1
-rw-r--r-- 1 197121 61 Sep 25 15:24 local.cpp

f:\git\usr\bin\cat *
int main (void)
{
        int x = 1;
        int y = 2;
        return x+y;
}
cl /Zi /W4 -GS /analyze /Od /nologo local.cpp /link /release /ENTRY:main /SUBSYSTEM:windows /FIXED
local.cpp

f:\git\usr\bin\ls -lg *.exe
-rwxr-xr-x 1 197121 2560 Sep 25 15:32 local.exe

description of options given to compiler and linker

/Zi = build with debug info embedded in pdbfile 
/w4 build with highest possible warning level
-GS disable stack cookie
/analyze run code analysis on the src files 
/Od disable optimization
/entry:main (no crt libs are sued so you need to set the entry point
/subsystem:windows  no cmd or no crt or no input output this is not a console app 
so you need to specify which subsystem will this program work on
/fixed disable relocations

opening the exe in ghidra and the function main copied as is

                             //
                             // .text 
                             // ram: 140001000-140001022
                             //
                             **************************************************************
                             *                          FUNCTION                          *
                             **************************************************************
                             int __fastcall main(int _Argc, char * * _Argv, char * * 
             int               EAX:4          <RETURN>
             int               ECX:4          _Argc
             char * *          RDX:8          _Argv
             char * *          R8:8           _Env
             undefined4        Stack[-0x14]:4 local_14                                XREF[2]:     140001004(W), 
                                                                                                   140001016(R)  
             undefined4        Stack[-0x18]:4 local_18                                XREF[2]:     14000100c(*), 
                                                                                                   140001013(*)  

|||||||||||||||||||| FUNCTION |||||||||||||||||||||||||||||||
                             Symbol Ref: main
                             entry                                           XREF[4]:     Entry Point(*), 1400000e0(*), 
                             .text$mn                                                     1400000e4(*), [more]
                             main
       140001000 48 83 ec 18     SUB        RSP,0x18
       140001004 c7 44 24        MOV        dword ptr [RSP + local_14],0x1
                 04 01 00 
                 00 00
       14000100c c7 04 24        MOV        dword ptr [RSP]=>local_18,0x2
                 02 00 00 00
       140001013 8b 04 24        MOV        EAX,dword ptr [RSP]=>local_18
       140001016 8b 4c 24 04     MOV        _Argc,dword ptr [RSP + local_14]
       14000101a 03 c8           ADD        _Argc,EAX
       14000101c 8b c1           MOV        EAX,_Argc
       14000101e 48 83 c4 18     ADD        RSP,0x18
       140001022 c3              RET
                             ********** main Exit ********** 

if you want to disable optimization for specific functions only and not wholesale with /Od you can use #pragmas see the screen shot below which shows vscode / vsdevcmdprompt / compilation all in one

replaced the image with a gif that does a "show and show" show

Answer 2

These are the compiler optimizations of the release build. You should build a debug build and then load it to ghidra