Problem with parallel build

[Michael Ringe]

The Makefile shown below sometimes fails to build the main target (app1).
Can anyone reproduce the error and explain what's wrong or confirm it's a bug?

All required files are in the attached .tar file. To reproduce the error,
make sure app1.o does not exist, then run "make -j2 app1" repeatedly.

On my machine (Intel core i5 551, openSuSE 11.3, make 3.81) make
fails after a few retries, because the link command is invoked before
app1.o is compiled.

--Michael


### --- Makefile start ---
AR := ar
CC := gcc

all: app1

# Link apps
app%: app%.o lib.a
        ${CC} ${@:app%=app%.o} lib.a -o $@

# Link lib.a
LIBSRCS := a b
lib.a: ${LIBSRCS:%=%.o}
        ${AR} r $@ ${LIBSRCS:%=%.o}

# Compile
%.o: src/%.c
        $(CC) -c -o $@ $<

# Dependencies
a.o: a.c lib.h
b.o: b.c lib.h
### --- Makefile end ---

make_bug.tar
Description: Unix tar archive