“mozconfig” — a play in two acts

Today while trying to figure out a strange build error with a student (mozconfig doesn’t like CR as much as CRLF), Ted decided to share a bit about the inner life of mozconfig.  I repeat it with permission for your reading pleasure.

Act I

• You run “make -f client.mk”
• The run_for_side_effects line runs mozconfig2client-mk
• This uses mozconfig-find to find the mozconfig to use
• Your mozconfig is sourced as a shell script
• In mozconfig2client-mk, “mk_add_options” is defined as a shell function that does some escaping and echoes whatever is listed after it to a temp file (ac_add_options in that file is defined as a no-op)
• client.mk then includes that temp file, so anything in it is treated as makefile source
• mk_add_options FOO=bar just winds up as the makefile assignment “FOO=bar”

Act II

• configure repeats this dance, but uses mozconfig2configure instead
• this does the reverse: ac_add_options does some quoting and echoes the result, mk_add_options is a no-op
• finally, configure sources the result as a shell script (with some hackery in there)

[end.]