Question

I am trying to understand how Linux launches a program. I read somewhere that some function in glibc calls the main function. Profiling with callgrind and looking at the call-graphs in Kcachegrind, I see below main which calls main. But I don’t understand this, a function can’t be named such. So my question is which function in the glibc actually starts the main function.

Answer 1

Following valgrind’s own help you’ll find this explanation for the option –show-below-main:

By default, stack traces for errors do not show any functions that
appear beneath main because most of the time it’s uninteresting C
library stuff and/or gobbledygook. Alternatively, if main is not
present in the stack trace, stack traces will not show any functions
below main-like functions such as glibc’s __libc_start_main.
Furthermore, if main-like functions are present in the trace, they are
normalised as (below main), in order to make the output more
deterministic.

As such, below main is not the function which calls main itself, but __libc_start_main.