tree 0f2beb47f5c00e95ab33f4c74d8ddb4538221644
parent 9d22e56178455d666b9774052b7b6f09291e7080
author Willy Tarreau <w@1wt.eu> 1553891417 +0100
committer Willy Tarreau <w@1wt.eu> 1554097387 +0200
encoding latin1

BUILD: re-implement an initcall variant without using executable sections

The current initcall implementation relies on dedicated sections (one
section per init stage) to store the initcall descriptors. Then upon
startup, these sections are scanned from beginning to end and all items
found there are called in sequence.

On platforms like AIX or Cygwin it seems difficult to figure the
beginning and end of sections as the linker doesn't seem to provide
the corresponding symbols. In order to replace this, this patch
simply implements an array of single linked (one per init stage)
which are fed using constructors for each register call. These
constructors are declared static, with a name depending on their
line number in the file, in order to avoid name clashes. The final
effect is the same, except that the method is slightly more expensive
in that it explicitly produces code to register these initcalls :

$ size  haproxy.sections haproxy.constructor
   text    data     bss     dec     hex filename
4060312  249176 1457652 5767140  57ffe4 haproxy.sections
4062862  260408 1457652 5780922  5835ba haproxy.constructor

This mechanism is enabled as an alternative to the default one when
build option USE_OBSOLETE_LINKER is set. This option is currently
enabled by default only on AIX and Cygwin, and may be attempted for
any target which fails to build complaining about missing symbols
__start_init_* and/or __stop_init_*.

Once confirmed as a reliable fix, this will likely have to be backported
to 1.9 where AIX and Cygwin do not build anymore.