The common case for this test suite is to quickly test that everything
returns the correct results. In this case, the second run of the test
suite under valgrind was just annoying, (and the user would often
interrupt it).
Now, do what is wanted in the common case by default (just run the
test suite), and require a run with "glcpp-test --valgrind" in order
to test with valgrind.
We recently added several tests that intentionally trigger
preprocessor errors. During valgrind-based testing, our test script
was noticing the non-zero return value from the preprocessor and
incorrectly flagging the valgrind-based test as failing.
To fix this, we make valgrind return an error code that is otherwise
unused by the preprocessor.
We're already using the return-value of cmp to print either PASS or
FAIL and in the case of failure, we're subsequently running and
showing the output of diff. So any warnings/errors from cmp itself are
not actually needed, and can be quite confusing.
As it turns out, 4 of our current tests are not valgrind clean,
(use after free errors or so), so this will be helpful for
investigating and fixing those.
