[neeeeees]

(Author here) Thanks for explaining this more succinctly than I can :)

Just one nitpick:

> decent amount of stuff that has to be done in main before you run _start

should read

> decent amount of stuff that has to be done in _start before you run main

Analogously, cleanup code like running global destructors usually happens in _start/CRT after main returns, but I skipped that in the post for the sake of brevity.

[oso2k]

I’d also argue

   > decent amount of stuff that CAN be done in _start before you run main

It’s all optional. Before I found the Linux kernel’s nolibc [0], I wrote a minimal C runtime based on bunch of stuff I read [1]. Only thing you really need to do is align the stack (at least on x86, amd64). You don’t get argc/argv/envp but main will still work.

[0] https://github.com/torvalds/linux/tree/master/tools/include/...

[1] https://github.com/lpsantil/rt0/blob/master/src/lib/00_start...

[saagarjha]

Generally this is either libc setup stuff, or things to support static initialization.