I've patched GNU make 3.80 to add better tracing, error reporting and
I have added a debugger. It is in
http://bashdb.sourceforge.net/remake-3.80+dbg.tar.gz
What I have here is very very preliminary; it there so one can get a
feel for what a debugger for GNU Make might look like. I've only been
able to compile this on GNU/Linux with RedHat 9.0 or
Debian. Compilations on other OS's seem to give problems in places
that as far as I can tell are not related to any of the changes I've
made. For the debugger, you should have GNU readline installed.
Okay, now some sample output. Here's a small test Makefile:
1: FOO=bar
2: all: foo
3: foo:
4: @echo hi > /dev/null
5: @fdafds
To get trace output, I've added the -x (or --trace) option. So:
./make -x -f bug2
produces:
bug2:2 all
bug2:3 foo
bug2:4 foo
echo hi > /dev/null
bug2:5 foo
fdafds
make: fdafds: Command not found
bug2:3: *** [foo] Error 127
One small thing to note above is that when -x is in effect the @'s to
turn off echoing are disregarded. So you see the "echo hi" and "fdafds"
in the output.
If you want a target backtrace on errors, add -E. For the above, this
adds to the end:
#0 foo at bug2:3
#1 all at bug2:2
I've also tried this the actual Makefile to the modified make. At
present it still gives too much output, but boy is it much more
comprehensible compared to what you get with "make -d"
Okay, now on to the debugger! Just add -X and you are put into the
debugger. Although I have a small command set right now with few
command formats or opitons, many of the most useful debugging commands
are there. You can set/delete breakpoints at a target, step execution,
restart or quit execution, turn on/off/toggle tracing, go up or down
the target backtrack stack and look at variables, Actually, there are
two kinds of print commands: "print" give a variable source/file
location and the value in symbolic terms.
For example when I run "p MAKE" inside the debugger (remake), I get:
(remake) p MAKE
(null):0 MAKE = $(MAKE_COMMAND)
The (null):0 means this is a builtin definition. However there is
another print which does full expansion of the variables. So if I run
x (examine) instead I get:
(null):0 MAKE = /src/local-cvs/remake/src/./make
In fact, "examine" doesn't need a variable name, it will work with a
string. So I could type "x This is $(MAKE)" or
"x $(bin_PROGRAMS) $(noinst_PROGRAMS)". For the latter, I get
make loadavg
Note, no location identification is given here (since what I put in
isn't a variable).
For those of you like myself who live inside of GNU Emacs, included in
the tarball is remake.el which uses on gud.el to provide running the
debugger inside GNU Emacs just as the way you'd do with perl, gdb, my
bash debugger. I also have a patched gud.el which contains the remake
debugger support. For front-end support such as this, I added "up" and
"down" debugger commands to postion you up or down in the Makefile
source.
Okay that's about it for now. I thought it would take a year or so to
get something I'm happy with. I'm a little ahead of schedule (but not
by much). I've been very pleased and surprised at how little work it
took for the gains I've gotten so far. It's a real pity no one has
undertaken this before, it hasn't been that hard.
Some interesting issues down the line will be in figuring out the
right level of display on a trace or maybe there would be several
levels: one doesn't want to step through every file dependency of
which most of them are satisfied. Right now I use the hueristic unless
a breakpoint is set I stop at targets that are explicitly mentioned on
the left-hand side. This is probably still too much. "phony targets"
and targets with commands may be too little.
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