Question

How do I generate the a.out file format with GCC on x86 architectures?

With NASM I can do this easily with the -f flag, for example:

nasm -f aout start.asm
objdump -a start.o

start.o:     file format a.out-i386-linux
start.o

On Linux, compiling .c files produces an ELF object file. How can I produce a.out files with GCC?

Answer 1

To generate the a.out format with gcc, your linker needs to be told to do so. You can do it by passing it flags from gcc thanks to the -Wl flag.

Here is what you would do for the a.out format:

gcc -Wl,--oformat=a.out-i386-linux file.c -o file.out

You can also display all formats supported by typing:

objdump -i