gcc generates unnecessary (?) instructions

Question

I decided to compile a very basic C program and take a look at the generated code with objdump -d.

int main(int argc, char *argv[]) {
    exit(0         


        

Answer 1

gcc generates unnecessary (?) instructions

Yes, because you invoked GCC without asking for any compiler optimizations.

My recommendation: compile with

gcc -fverbose-asm -O2 -S test.c

then look inside the generated test.s assembler code.

BTW, most of the code is from crt0, which is given by, not emitted by, gcc. Build your executable with gcc -O2 -v test.c -o testprog to understand what GCC really does. Read documentation of GCC internals.

Since GCC is free software, you are allowed to look inside its source code and improve it. But the crt0 stuff is tricky, and operating system specific.

Consider also reading about linkers and loaders, about ELF executables, and How to write shared libraries, and the Linux Assembler HowTo.