CVS commit: src/usr.bin/make

["Roland Illig" <rillig%netbsd.org@localhost>]

Module Name:    src
Committed By:   rillig
Date:           Sun Feb 14 22:48:17 UTC 2021

Modified Files:
        src/usr.bin/make: var.c

Log Message:
make: clean up memory management in evaluation of expressions

The condition "st->newValue.str != val" in ApplySingleModifier made the
memory management look more complicated than it really was.  Freeing an
object based on another object's value is harder to understand than
necessary.

To fix this, the "current value" of the expression is now stored in
ApplyModifiersState, and it gets updated in-place by the ApplyModifier
functions.  This reduces the number of parameters for the ApplyModifier
functions.

Accessing the current value of the expression is now more verbose than
before (st->value.str instead of the simple val).  To compensate for
this verbosity, ApplyModifiersIndirect is now much easier to understand
since there is no extra "current value" floating around.

There is still room for improvement.  In ApplyModifiers, passing an FStr
in and returning another (or possibly the same) makes it difficult to
understand memory management.  Adding a separate Expr type that outlives
the ApplyModifiersState will make this easier, in a follow-up commit.


To generate a diff of this commit:
cvs rdiff -u -r1.820 -r1.821 src/usr.bin/make/var.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.