[PATCH 3/6] compat: disable -Wunused-parameter in 3rd-party code

We carry some vendored 3rd-party code in compat/ that does not build cleanly with -Wunused-parameters. We could mark these with UNUSED, but there are two reasons not to:

  1. This is code imported from elsewhere, so we'd prefer to avoid
     modifying it in an invasive way that could create conflicts if we
     tried to pull in a new version.

  2. These files don't include git-compat-util.h at all, so we'd need to
     factor out (or repeat) our UNUSED macro.

In theory we could modify the build process to invoke the compiler with the extra warning disabled for these files, but there are tricky corner cases there (e.g., for NO_REGEX we cannot assume that the compiler understands -Wno-unused-parameter as an option, so we'd have to use our detect-compiler script).

Instead, let's rely on the gcc diagnostic #pragma. This is horribly unportable, of course, but it should do what we want. Compilers which don't understand this particular pragma should ignore it (per the standard), and compilers which do care about "-Wunused-parameter" will hopefully respect it, even if they are not gcc (e.g., clang does).

Signed-off-by: Jeff King <peff@peff.net>
---
 compat/nedmalloc/nedmalloc.c | 2 ++
 compat/regex/regcomp.c       | 2 ++
 2 files changed, 4 insertions(+)