Inconsistent behaviour when building in parallel

[Dirk Heinrichs]

Hello,

I'm using GNU make 3.81 (on Linux, if this is important) and see strange 
behaviour in parallel builds with the following Makefile:

file1.txt file2.txt: file.in
        cat $< >file1.txt|tee file2.txt

test: file1.txt file2.txt
        cat $^ >$@

In a normal build, make does the right thing:

% make test
cat file.in >file1.txt|tee file2.txt
cat file1.txt file2.txt >test

In case of a parallel build, the "cat ... | tee ..." command for file[12].txt 
is executed twice, which should not happen:

% make -j 2 test
cat file.in >file1.txt|tee file2.txt
cat file.in >file1.txt|tee file2.txt
cat file1.txt file2.txt >test

Bye...

        Dirk

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