diff options
| author | Richard Levitte <levitte@openssl.org> | 2016-03-10 01:10:54 +0100 |
|---|---|---|
| committer | Richard Levitte <levitte@openssl.org> | 2016-03-17 19:08:49 +0100 |
| commit | a4a7174890c365283daa9d5faf1f63ed3afe5e7b (patch) | |
| tree | 46dae0b18d981585bc812d450d822256dcc9be8a /Configurations | |
| parent | 2b6b606c7b9db8bfde3bd0aaa90b19049f8f6311 (diff) | |
Start documenting Configure internals
This is a living document, everyone is encouraged to add to it.
Implementation details as well as broader implementation philosophy
has a place here.
I'm starting with documentation of the how conditions in build.info
files are treated.
Reviewed-by: Rich Salz <rsalz@openssl.org>
Diffstat (limited to 'Configurations')
| -rw-r--r-- | Configurations/INTERNALS.Configure | 136 |
1 files changed, 136 insertions, 0 deletions
diff --git a/Configurations/INTERNALS.Configure b/Configurations/INTERNALS.Configure new file mode 100644 index 0000000000..b28305deca --- /dev/null +++ b/Configurations/INTERNALS.Configure @@ -0,0 +1,136 @@ +Configure Internals +=================== + +[ note: this file uses markdown for formatting ] + +Intro +----- + +This is a collection of notes that are hopefully of interest to those +who decide to dive into Configure and what it does. This is a living +document and anyone is encouraged to add to it and submit changes. +There's no claim for this document to be complete at any time, but it +will hopefully reach such a point in time. + + +---------------------------------------------------------------------- + +Parsing build.info files, processing conditions +----------------------------------------------- + +Processing conditions in build.info files is done with the help of a +condition stack that tell if a build.info should be processed or if it +should just be skipped over. The possible states of the stack top are +expressed in the following comment from Configure: + + # The top item of this stack has the following values + # -2 positive already run and we found ELSE (following ELSIF should fail) + # -1 positive already run (skip until ENDIF) + # 0 negatives so far (if we're at a condition, check it) + # 1 last was positive (don't skip lines until next ELSE, ELSIF or ENDIF) + # 2 positive ELSE (following ELSIF should fail) + +Ground rule is that non-condition lines are skipped over if the +stack top is > 0. Condition lines (IF, ELSIF, ELSE and ENDIF +statements) need to be processed either way to keep track of the skip +stack states, so they are a little more intricate. + +Instead of trying to describe in words, here are some example of what +the skip stack should look like after each line is processed: + +Example 1: + +| IF[1] | 1 | | +| ... whatever ... | | this line is processed | +| IF[1] | 1 1 | | +| ... whatever ... | | this line is processed | +| ELSIF[1] | 1 -1 | | +| ... whatever ... | | this line is skipped over | +| ELSE | 1 -2 | | +| ... whatever ... | | this line is skipped over | +| ENDIF | 1 | | +| ... whatever ... | | this line is processed | +| ELSIF[1] | -1 | | +| ... whatever ... | | this line is skipped over | +| IF[1] | -1 -1 | | +| ... whatever ... | | this line is skipped over | +| ELSIF[1] | -1 -1 | | +| ... whatever ... | | this line is skipped over | +| ELSE | -1 -2 | | +| ... whatever ... | | this line is skipped over | +| ENDIF | -1 | | +| ... whatever ... | | this line is skipped over | +| ENDIF | | | + +Example 2: + +| IF[0] | 0 | | +| ... whatever ... | | this line is skipped over | +| IF[1] | 0 -1 | | +| ... whatever ... | | this line is skipped over | +| ELSIF[1] | 0 -1 | | +| ... whatever ... | | this line is skipped over | +| ELSE | 0 -2 | | +| ... whatever ... | | this line is skipped over | +| ENDIF | 0 | | +| ... whatever ... | | this line is skipped over | +| ELSIF[1] | 1 | | +| ... whatever ... | | this line is processed | +| IF[1] | 1 1 | | +| ... whatever ... | | this line is processed | +| ELSIF[1] | 1 -1 | | +| ... whatever ... | | this line is skipped over | +| ELSE | 1 -2 | | +| ... whatever ... | | this line is skipped over | +| ENDIF | 1 | | +| ... whatever ... | | this line is processed | +| ENDIF | | | + +Example 3: + +| IF[0] | 0 | | +| ... whatever ... | | this line is skipped over | +| IF[0] | 0 -1 | | +| ... whatever ... | | this line is skipped over | +| ELSIF[1] | 0 -1 | | +| ... whatever ... | | this line is skipped over | +| ELSE | 0 -2 | | +| ... whatever ... | | this line is skipped over | +| ENDIF | 0 | | +| ... whatever ... | | this line is skipped over | +| ELSIF[1] | 1 | | +| ... whatever ... | | this line is processed | +| IF[0] | 1 0 | | +| ... whatever ... | | this line is skipped over | +| ELSIF[1] | 1 1 | | +| ... whatever ... | | this line is processed | +| ELSE | 1 -2 | | +| ... whatever ... | | this line is skipped over | +| ENDIF | 1 | | +| ... whatever ... | | this line is processed | +| ENDIF | | | + +Example 4: + +| IF[0] | 0 | | +| ... whatever ... | | this line is skipped over | +| IF[0] | 0 -1 | | +| ... whatever ... | | this line is skipped over | +| ELSIF[0] | 0 -1 | | +| ... whatever ... | | this line is skipped over | +| ELSE | 0 -2 | | +| ... whatever ... | | this line is skipped over | +| ENDIF | 0 | | +| ... whatever ... | | this line is skipped over | +| ELSIF[1] | 1 | | +| ... whatever ... | | this line is processed | +| IF[0] | 1 0 | | +| ... whatever ... | | this line is skipped over | +| ELSIF[0] | 1 0 | | +| ... whatever ... | | this line is skipped over | +| ELSE | 1 2 | | +| ... whatever ... | | this line is processed | +| ENDIF | 1 | | +| ... whatever ... | | this line is processed | +| ENDIF | | | + |