parse.h #4

# Change User Description Committed
#4 1270 Matt Armstrong In prep for publishing all my patches to jam.
#3 1088 Matt Armstrong Merge in changes from upstream.
#2 293 Matt Armstrong Fix a crash bug in jam by adding reference counting to the
PARSE struct.  The bug occurs when a rule re-defines
itself.  This can only happen by using the include statement,
as follows.

JamfileA:
----------------------------------------------------
rule DoInclude {
    ECHO JamfileA DoInclude $(<) start ;
    include $(<) ;
    ECHO JamfileA DoInclude $(<) end ;
}
DoInclude JambileB ;
----------------------------------------------------

JamfileB:
----------------------------------------------------
rule DoInclude {
    ECHO JamfileB DoInclude ;
}
DoInclude JambileC ;
----------------------------------------------------

With these two jamfiles you can reproduce the crash bug
by running "jam -fJamfileA".  If that doesn't work,
change parse_free() such that it memsets PARSE struct being
freed to something bogus like 0x03 and try again (or use
Purify and watch the free memory read warnings).

The problem is that compile_setcomp() just frees the PARSE
without regard for the possibility that it might be executing.
In the case above, JamfileA's DoInclude is re-defined by
JamfileB while it is still being executed.

The simple fix is to just have compile_setcomp() not free the
PARSE.  This would introduce a memory leak for every re-defined
rule.

My fix introduces reference counting of the PARSE struct.  A
PARSE is allocated with a reference count of 1 and when it
goes to 0 it is freed.  Every place that was a parse_free() is
now a parse_decref().  In addition, compile_rules() increments
the reference count of its PARSE around the calls to its left
and right functions.

Perhaps there a better fix!
#1 289 Matt Armstrong Initial branch.
//guest/perforce_software/jam/src/parse.h
#1 2 laura Add Jam/MR 2.2 source