Using g_slice_set_config() fails with newer glib because the slice allocator
now has a static constructor that runs when glib is loaded, consequently
emitting a noisy error message which confuses people into believing it's the
root of their problems.
The only way left to force the slice allocator to use "system" malloc (in
practice, jemalloc) is to set the G_SLICE environment variable to
always-malloc, and that needs to happen before glib is loaded.
Fortunately, the firefox and plugin-container executables don't depend on
glib. Unfortunately, webapprt does, so the problem remains for web apps
running through it. xpcshell and other executables that depend on libxul
directly (as opposed to loading it dynamically) are not covered either.
Constructing kComponentsInterfaceShimMap required a static constructor
on some compilers, due to a non-constexpr constructor and the necessity
of copying non-constexpr things like nsIID. This static constructor is
large (several kilobytes of object code on x86-64) and completely
unnecessary.
To fix this, let's add a constexpr (well, MOZ_CONSTEXPR) constructor to
ComponentsInterfaceShimEntry. This change alone doesn't completely
solve our problem, because the nsIID member still needs to be copied.
But doing that copying is silly: we only use the IID for constructing a
ShimInterfaceInfo in ShimInterfaceInfo::MaybeConstruct, and the
ShimInterfaceInfo constructor takes a const reference. So let's store a
const reference in ComponentsInterfaceShimEntry, too, and make that
structure significantly smaller in the process.
PostTimerEvent is only called by the timer thread, which is already able
to access private members of nsTimerImpl; there's no reason for
PostTimerEvent to be public.
GetTracedTask() is only called from nsTimerImpl itself, so it doesn't
need to be public. GetTLSTraceInfo() is called from the timer thread,
which has access to our private members already.
This patch factors out the existing capacity calculation code in HashShift()
into a new function called BestCapacity(), and then reuses it for
post-enumeration shrinking.
BestCapacity() computes capacity with |CeilingLog2(ceil(length * 4 / 3))|,
which ensures a minimum capacity while respecting the "max 75% full" and
"capacity is a power of two" constraints. In contrast, the old post-enumeration
shrink calculation was |CeilingLog2(length + length/2)|, which gives higher
results in some cases. (Both calculations also ensured the capacity wasn't too
small.) E.g. if length is 48, the former calculation will give 64, while the
latter will give 128.
Therefore, post-enumeration shrinking will no longer give a
larger-than-necessary capacity some cases. This feels like the right thing to
do in isolation, and making it consistent with HashShift() -- used during table
construction -- is also good.
This change splits PLDHashTable::Iterator::NextEntry() into two separate
functions, which allow you to get the current element and advance the iterator
separately, which means you can use a for-loop to iterate instead of a
while-loop.
As part of this change, the internals of PLDHashTable::Iterator were
significantly changed and simplified (and modelled after js::HashTable's
equivalent code). It's no longer duplicating code from PL_DHashTableEnumerator.
The chaos mode code was a casualty of this, but given how unreliable that code
has proven to be (see bug 1173212, bug 1174046) this is for the best. (We can
reimplement chaos mode once PLDHashTable::Iterator is back on more solid
footing again, if we think it's important.)
All these changes will make it much easier to add an alternative Iterator that
removes elements, which was turning out to be difficult with the prior code.
In order to make the for-loop header usually fit on a single line, I
deliberately renamed a bunch of things to have shorter names.
In summary, you used to write this:
PLDHashTable::Iterator iter(&table);
while (iter.HasMoreEntries()) {
auto entry = static_cast<FooEntry*>(iter.NextEntry());
// ... do stuff with |entry| ...
}
// iter's scope extends beyond here
and now you write this:
for (auto iter = table.Iter(); !iter.Done(); iter.Next()) {
auto entry = static_cast<FooEntry*>(iter.Get());
// ... do stuff with |entry| ...
}
// iter's scope doesn't reach here
