CVS commit: src/usr.bin/make

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

Module Name:    src
Committed By:   rillig
Date:           Sun Dec 12 13:43:47 UTC 2021

Modified Files:
        src/usr.bin/make: str.h

Log Message:
make: fix memory leak in LazyBuf

This affects many operations on variable expressions.  Those using
LazyBuf_Done are affected, those using LazyBuf_DoneGet aren't.

$ cat <<'EOF' > lazybuf-memleak.mk
.for i in ${:U:range=5}
.  for j in ${:U:range=1000}
.    for k in ${:U:range=1000}
.      if 0 && ${VAR:Dpattern\: that needs unescaping}
.      endif
.    endfor
.  endfor
.endfor

all:
        @ps -o vsz -p ${.MAKE.PID} | sed 1d
EOF

Before using LazyBuf for the modifier ':D':

    $ make-2021.04.14.16.12.26 -r -f lazybuf-memleak.mk
        VSZ     RSZ
    1357136 1336432

Using LazyBuf for the modifier ':D':

    $ make-2021.04.14.16.59.34 -r -f lazybuf-memleak.mk
        VSZ     RSZ
    1590864 1574164

This commit alone allocates around 150 MB more data, which matches
5_000_000 strings * 30 bytes/string.

It looks very wrong that the above simple makefile uses 1.3 GB of RAM at
all, and it had already done this in 2017, long before LazyBuf was
introduced.  Before 2017.01.30.02.46.20, the above test makefile reports
way smaller numbers, but that's because the modifier ':range' did not
exist back then.


To generate a diff of this commit:
cvs rdiff -u -r1.11 -r1.12 src/usr.bin/make/str.h

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