"set foo"

[Eli Zaretskii <eliz at gnu dot org>]

I had a problem today whereby GDB did not recognize a certain struct
when processing a .gdbinit file.  Trying to understand what's going
on, I noticed that after stepping through the program for a while, the
struct became known at some point.

I assume that this is because of delayed reading of the symbol tables,
but my question is about something else.  I noticed that the .gdbinit
file supplied with Emacs has this line at its beginning:

  set main

A comment there says that this is so some variables from the binary
are available when .gdbinit is processed.  I understand that this
command somehow manages to force GDB to read the relevant portions of
the symbol tables, but what I don't understand is what is the
semantics of saying "set foo" in GDB where foo is some function.  What
does this command do, exactly?

TIA