Calling NASM from a C program using system() produces different object code then calling using Bash

Question

I've implemented a reasonably good optimizing compiler (for a toy language), and have come across a rather puzzling scenario. I can take an input file and produce assembly from it, so in that respect the "compiler" is finished. If I take that assembly file assemble it with NASM and link it to my runtime support library with G++ (the runtime needs libstdc++), I get a working executable, with no errors. However, I'd like to be able to compile to an executable in one command, so I added some calls to system to my compiler, passing the EXACT SAME COMMANDS as I was using in bash. When I run the compiler, it seems to assembly properly, but the linking step (again, using g++) fails with an undefined reference to main . Confused, I attempted to link manually (without reassembling, so I was using the object file produced by the NASM run with system , and received the same error. If I reassemble using the new compiler's assembly output, I have no problems, which has led be to believe that NASM is the problem. Like I said, the commands are exactly the same (I literally copied and pasted them just to make sure after the first time). Is this environment variables or something? What's going on?

EDIT: I manually assembled an object file, again using the same command as the one in the compiler, and I did a vim diff between the two. The compiler-generated one seems to only contain the ELF header.

EDIT 2: A screenshot of the diff

EDIT 3: I tried using system to call a Perl script that in turn would call NASM and G++, still no luck.

Answer 1

Fixed it! It was the file not being flushed due to a race condition. Thanks for all the help, much appreciated.