Samba uses these flags, so be friendly.

tdb1 has tdb_reopen/tdb_reopen_all, which you are supposed to call
after a fork().  But we can detect PID changes whenever we grab a lock,
which is to say, before we do anything.

We currently assume that pread and pwrite work, so the only problem
with fork() is if we are holding locks and expect them to still be
there in the child.  This is unusual, but most likely caused by a
fork() inside a transaction.  In such cases, allow the child to unlock
without complaint; they can then use the TDB as expected.

Performance before and after shows no measurable speed difference:

Total of 5 runs of tools/speed 100000:
Before:
	Adding: 18899ns
	Finding: 7040ns
	Missing: 5802ns
	Traversing: 6466ns
	Deleting: 12607ns
	Re-adding: 14185ns
	Appending: 20770ns
	Churning: 93845ns

After:
	Adding: 18073ns
	Finding: 6795ns
	Missing: 5549ns
	Traversing: 6333ns
	Deleting: 12313ns
	Re-adding: 13835ns
	Appending: 20343ns
	Churning: 92208ns

We also change tdb_chainunlock not to return an error (as per the
other locking functions: we log a message, but don't return an error).

This isn't on RHEL4, for example: isascii() and isblank() are not in
C89.

I don't quite know why, but this started happening to me.  We should
handle it anyway.

gcc gave a warning:
	tools/ccanlint/ccanlint.c:230:19: error: ‘c’ may be used uninitialized in this function

Which indicated that test dependency printing was broken: we need to
loop through the tests!  Also, we haven't parsed options yet, so
verbose is never true: move it to later and make it depend on -vvv.

memmem(), which searches for one bytestring in a longer
bytestring is one of those functions that should be standard, but
isn't.  This patch adds a ccan configurator test for the function
so that modules can use or replace it as necessary.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

Simplest fix is to use const where possible, and use a different var for
asprintf and string literals in login.c.

Tests don't compile otherwise, so fix that up (ccanlint now tests with
reduced features, so this became clear).

Add a license tag (though it's a weird BSD variant), remove whitespace, and
avoid void pointer arithmetic.

They expect to be linked against the module objects.

Just grab the tokens for the simple case: this allows the ccanlint
reduce_features test to work on eg. ccan/cast.

This means we change some minor tests to "never fail", eg. whitespace
or documentation tests.  Note that pass/fail is independent of the
score for a test.

Be a little more careful with const.

Shown up by -Wwrite-strings.

Wpointer-arith is useful for spotting GCC-isms which do arithmetic on
void pointers.  Wwrite-strings treats string constants as const char *,
which is sane (but bad for legacy code).

Same fix as we used for ccan/typesafe_cb.

No only does this give us one more ccanlint point, it clears the way
to see if we introduce a *real* memory leak later.

This need shows up most clearly with opt_usage_and_exit and gcc's
-Wwrite-strings, where string literals become "const char *".  Our
callbacks should take const void *: since we overload the arg field
already (to hold table size) it make sense to turn it into a proper
union.

Headers should stand alone; we use NULL, so we should make sure it's defined.

I thought using sizeof() comparison to compare the types was clever,
but it doesn't work on void pointers, as sizeof(void) is illegal.

In this case, "work" means "fail to compile cleanly".

Don't implicitly cast away const in the tests.

In particular, avoid doing arithmetic on NULL; decay the function to a
pointer using a trinary conditional instead.

It's common to want to create a struct tdb_data which contains a const
pointer, so add a helper to do so, and use it to clean up other -Wcast-qual
warnings.

Samba uses -Wcast-qual to warn about casting away const.  The kind of
coders who care about const correctness are likely to turn that option
on, so we should make sure it's compatible with cast_const().