Re: [RFC 2/2] Make misuse of get_pathname() buffers detectable by valgrind

On Tue, Sep 27, 2011 at 11:28 AM, Michael Haggerty [off-list ref] wrote:

A temporary buffer produced by get_pathname() is recycled after a few
subsequent calls of get_pathname().  The use of such a buffer after it
has been recycled can result in the wrong file being accessed with
very strange effects.  Moreover, such a bug can lie dormant until code
elsewhere is changed to use a temporary buffer, causing very
mysterious, nonlocal failures that are hard to analyze.

Add a second implementation of get_pathname() (activated if the
VALGRIND preprocessor macro is defined) that allocates and frees
buffers instead of recycling statically-allocated buffers.  This does
not make the problem less serious, but it turns the errors into
access-after-free errors, making it possible to locate the guilty code
using valgrind.

Signed-off-by: Michael Haggerty <redacted>
---

I believe that it is frowned upon to use #ifdefs in git code, but no
good alternative is obvious to me for this type of use.  Suggestions
are welcome.

Enable the code based on an environment variable, e.g.
GIT_DEBUG_FENCE, then enable it by default in test-lib.sh :-)
-- 
Duy