[Boost-build] Caching failed configuration checks

Subject: [Boost-build] Caching failed configuration checks
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2012-04-04 14:31:16

AMDG

I'm finding it a little annoying that
the configure checks always re-run
if they fail, even though they get
cached when they succeed.

For implementation, what I'm thinking right now is:

A new Jam builtin:

# If updating target fails, the output of the
# failing command is written to error-target.
# error-target is deleted whenever there is
# an attempt to update target.
# If error-target is up to date, then
# attempts to build target will immediately
# fail without running any commands.
rule SAVE_FAILURE ( target : error-target )

In configure, we can then use:

local error-target = ... ;
DEPENDS $(error-target) : $(target) ;
LEAVES $(error-target) ;
SAVE_FAILURE (target) : $(error-target) ;

Thoughts?  Any better ideas about how to
solve this?  Is it possible to avoid
modifying jam via some magic involving
FAIL_EXPECTED/__ACTION_RULE__/...?

In Christ,
Steven Watanabe