Summary:
IdleTime unit test has been failing randomly (#5996886). The
event base loop calculates an exponentially moving average of loop busy
time in each loop. In the test, the busy time is initialized to 5900 and
each loop runs more than 8000 us. In normal case decaying of the
previous loop busy time will take 6 loops to  move this average to >6000.
But if the test is running on a heavily loaded machine the busy+idle time
a loop is longer than it should be, causing the decaying happen faster.
This diff skips this test if this happens.

Test Plan:
It won't affect anything if running on my devserver. It only
helps on a heavily loaded contbuild host.

Reviewed By: alandau@fb.com

Subscribers: folly-diffs@

FB internal diff: D1788450

Tasks: 5996886

Signature: t1:1788450:1421460774:1ec575c50f881e10b5a0208717fe68164f0d0f57

Test Plan: checked this is the right function name

Reviewed By: ngbronson@fb.com

Subscribers: folly-diffs@

FB internal diff: D1788386

Signature: t1:1788386:1421453582:82d0c4685c1bd2d888f5974fd2a998ebbc27a9b5

Summary:
The big comment block at the top of MPMCQueue had a non-sense
sentence resulting from a merge conflict, and also didn't include
details about ordering or recommended patterns for handling consumer
shutdown.

Test Plan: comment change

Reviewed By: lesha@fb.com

Subscribers: folly-diffs@

FB internal diff: D1788230

Signature: t1:1788230:1421451643:7c768c2b127499e3f2b06ee241fba851b4ed2a29

Summary:
We want all socket options to be applied to the listen sockets too.

The old code here that only applied SO_KEEPALIVE is a bit superstitious.
Not all options will be inherited by accept()ed sockets, but that's
fine.  We set them again post-accept().

Applying all these options to the listening sockets will fix at least
one long standing bug, which is that QoS is not set correctly for the
first few packets in a flow.  This also will let us do the right thing
when we gain the ability to set TCP_MAXSEG in D1741753.

Test Plan: fbmake runtests & canary in prod

Reviewed By: afrind@fb.com, davejwatson@fb.com

Subscribers: jsedgwick, satadru, trunkagent, fugalh, exa, folly-diffs@, agartrell

FB internal diff: D1745182

Tasks: 2911597

Signature: t1:1745182:1418860157:045680a91b153482bcd4a014894fb28059955d06

Summary:
My initial change to avoid the -Wsign-compare error neglected
the fact that the difference of two unsigned types is also
unsigned. That broke some unicorn tests, as seen in D1776343,
which worked around the problem by changing the type of
bitOffset_ like this: s/unsigned int/size_t.

The real problem lay in the distance_to function, which computed
the signed difference of two bitOffset_ values.
To work properly with the narrower unsigned type,
we could either first widen each operand to ssize_t
before computing their parenthesized difference, or
(as Philip suggested and I prefer), just drop the
parentheses and let the signedness of the preceding
operands ensure that each successive intermediate
result is also signed.

Test Plan:
Choose one of the failing tests, and ensure it now passes:

fbconfig -r unicorn/diskindex4/test:doc_map_test
fbmake runtests

Also run all unicorn tests, for good measure (still waiting):
fbconfig -r unicorn && fbmake runtests

Reviewed By: philipp@fb.com, andrei.alexandrescu@fb.com

Subscribers: trunkagent, net-systems@, folly-diffs@

FB internal diff: D1776624

Tasks: 5941250

Signature: t1:1776624:1420872874:b1ea8a3f23f21269aa65cbe1647e86a8f622a710

Blame Revision: D1770613

Summary:
it's redundant and we shouldn't encourage it, so i'm changing all callsites
i changed docs as well

Test Plan: wait for contbuild

Reviewed By: hans@fb.com

Subscribers: trunkagent, fbcode-common-diffs@, hero-diffs@, cold-storage-diffs@, targeting-diff-backend@, adityab, everstore-dev@, zhuohuang, darshan, micha, folly-diffs@, wch, lins, tingy, jsedgwick

FB internal diff: D1784667

Tasks: 5936469

Signature: t1:1784667:1421364620:83169739320e5342d28a744e3689794f16108fea

Summary: grep around for wangle, adjust where appropriate

Test Plan: contbuild

Reviewed By: hans@fb.com

Subscribers: trunkagent, fbcode-common-diffs@, ruibalp, zeus-diffs@, vikas, targeting-diff-backend@, alandau, mwa, jgehring, zhguo, jying, darshan, fuegen, mshneer, folly-diffs@, lins, maxwellsayles, jsedgwick

FB internal diff: D1777581

Tasks: 5960242

Signature: t1:1777581:1421361395:2ee8bfeca76dafe7376a217c66e0a4eaf3ef416a

Summary:
* folly/MPMCQueue.h (waitForTurn): My changes to accommodate
-Wsign-compare introduced a bug that could cause lots of wasted CPU.
(See @scottf's comments on the blamed patch.)
Subtraction involving an unsigned type will always yield an unsigned
result, and there was at least this one instance where the result
would sometimes have to be a small negative number.  Instead, we'd
get approximately UINT32_MAX.  The fix is to explicitly cast the
difference to a signed type.

Test Plan:
Run this and note there is no error:
(this ensures it remains -Wsign-compare-clean with gcc-4.9)

fbconfig --platform-all=gcc-4.9-glibc-2.20 tao/server && fbmake dbgo

Before this change, running the mpmc_queue_test test would get
timeout errors ~8 in 100 runs.  Confirm that with this patch, now
there is no type of failure. I.e., run these commands and ensure
the grep prints nothing:

fbconfig folly/test:mpmc_queue_test
for i in $(seq 100); do fbmake runtests_dbgo >& makerr-$i; done
grep -E '(TIMEOUT|FATAL|FAIL).* [1-9]' makerr-*

Reviewed By: hans@fb.com

Subscribers: trunkagent, scottf, folly-diffs@

FB internal diff: D1783672

Tasks: 5941250

Signature: t1:1783672:1421350260:d7d306e8cf3ed3ee636d06228e1f24a2c2796b54

Blame Revision: D1766722

Summary:
configure seems to think ubuntu 14.04 doesn't have pthread_atfork, which seems wrong?! But this test seems to fail if we don't have it on some platform anyway.  Not sure the right fix, just disable it for now?

Test Plan: watch https://ci-builds.fb.com/job/folly/

Reviewed By: hans@fb.com

Subscribers: doug, folly-diffs@

FB internal diff: D1783046

Signature: t1:1783046:1421348575:d279877abcc597a04c285092a5e5e53406922d5a

Blame Revision: D1768669

Summary:
i) FOLLY_HAVE_INT128_T definition is duplicated and is getting set to 1 on android. deleted that.
ii) we dont have pthread_spinlock_t and pthread_atfork on android, the former is absent apple as well
iii) a condition got flipped in D1768669. __ANDROID__ implies !FOLLY_HAVE_PTHREAD_SPINLOCK_T. fixed that

Test Plan:
- fbconfig -r folly && fbmake
- ran folly build with buck as well
- synced to fb4a and it builds

Reviewed By: seanc@fb.com

Subscribers: doug, seanc, folly-diffs@

FB internal diff: D1783579

Signature: t1:1783579:1421350138:9301303f77784e7bdb851e3f643751078457b025

Summary:
unfortunately, can't use atomics now that a weak_ptr is stored instead of a raw ptr, hence the additional singleton locks
might want to make an overload of via() that takes shared_ptr to integrate more easily? or change via() to store a shared_ptr (and make it non-owning if a raw ptr is passed)

Test Plan: unit

Reviewed By: davejwatson@fb.com

Subscribers: jsedgwick, trunkagent, fugalh, folly-diffs@

FB internal diff: D1764359

Tasks: 5002442

Signature: t1:1764359:1420845340:349ea88091d7ca4ee386b54aec599647341fadd4

Summary: http://www.cplusplus.com/reference/map/map/at/

Test Plan: unittest

Reviewed By: ldbrandy@fb.com

Subscribers: trunkagent, jkong, folly-diffs@

FB internal diff: D1773996

Signature: t1:1773996:1421176834:33c8b39f03bf085ca2dd45df113cba948d0f2dd0

Summary:
This is a bootstrap script for building folly on osx. I attempted to make it Just Work™ for anyone who uses Homebrew (http://brew.sh/) but even if it doesn't work out of the box it should be instructive for the motivated developer on OSX.

Facebook:
In #5134151 Wangle used to not build, because something was using a futex. But that seems to have been rectified (or the build problems are hiding in headers that aren't used in the libfolly build).

I'll also update https://our.intern.facebook.com/intern/wiki/Folly/BuildingOnMac to point people to this script instead.

Test Plan:
Tested on my laptop which is running Yosemite (10.10.1)
Build, then inspect `otool -L .libs/*dylib`

Reviewed By: davejwatson@fb.com

Subscribers: folly-diffs@, exa

FB internal diff: D1765248

Tasks: 5134151

Signature: t1:1765248:1420500905:bc5da97a0446f502cb2badc85c9004ff0a62027a

Summary:
SpookyHashTest now needs libgtestmain to be linked
(https://phabricator.fb.com/D1775555).

https://ci-builds.fb.com/job/folly/1570/console

Test Plan:
Don't have Ubuntu setup, but this should fix it. Will kick off jenkins
build.

Reviewed By: andrewjcg@fb.com

Subscribers: folly-diffs@

FB internal diff: D1779604

Signature: t1:1779604:1421174608:de865529d728e943288b52c0d63ebb712eda094f

Blame Revision: D1775555

Summary: Namespace change. Next up is to extract the Executors into folly/executors/

Test Plan: wait for contbuild

Reviewed By: davejwatson@fb.com

Subscribers: jsedgwick, trunkagent, fbcode-common-diffs@, chaoyc, search-fbcode-diffs@, lars, davejwatson, ruibalp, hero-diffs@, zeus-diffs@, andrewcox, vikas, mcduff, cold-storage-diffs@, unicorn-diffs@, ldbrandy, targeting-diff-backend@, netego-diffs@, abirchall, fugalh, adamsyta, atlas2-eng@, chenzhimin, mpawlowski, alandau, bmatheny, adityab, everstore-dev@, zhuohuang, mwa, jgehring, prometheus-diffs@, smarlow, akr, bnitka, jcoens, benj, laser-diffs@, zhguo, jying, darshan, micha, apodsiadlo, alikhtarov, fuegen, dzhulgakov, jeremyfein, mshneer, folly-diffs@, wch, lins, tingy, hannesr, maxwellsayles

FB internal diff: D1772779

Tasks: 5960242

Signature: t1:1772779:1420751149:bc0b9220be25f1d46d9cef3fdeaa9c3681217aff

Summary: Also add the `@buckify` tag to keep these automatically synced.

Test Plan: built and tested with buck and fbconfig/fbmake

Reviewed By: robbert@fb.com

Subscribers: trunkagent, sdwilsh, fugalh, folly-diffs@, jsedgwick

FB internal diff: D1775555

Signature: t1:1775555:1420840948:e9a2e86379be71b7d953fa53a727e51d2541b011

Summary: D1770613 made bitsPerBlock 32 bit. Sadpanda.

Test Plan: _bin/unicorn/diskindex4/test/doc_map_test --gtest_filter=DocMap/DocMapTest.Deleted/23

Reviewed By: meyering@fb.com

Subscribers: net-systems@, folly-diffs@

FB internal diff: D1776343

Tasks: 5968993

Signature: t1:1776343:1420852923:f35166dd9023a701ff16467710131f821810215a

Blame Revision: D1770613

Summary:
* folly/dynamic-inl.h (format): Add an explicit
int-to-size_t cast (that is ok because we've just ensured
it is non-negative) to avoid this error from gcc-4.9:

folly/dynamic-inl.h:953:29: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]

Test Plan:
Run this and note there are fewer errors than before:
fbconfig --platform-all=gcc-4.9-glibc-2.20 -r folly && fbmake dbgo

Reviewed By: delong.j@fb.com

Subscribers: trunkagent, folly-diffs@

FB internal diff: D1773242

Tasks: 5941250

Signature: t1:1773242:1420822301:b1e3c065cd25728c77957ce9e1f52e884ba8693b

Summary:
There were many templates instantiated with signed types.
Changing them to unsigned avoids the compilation failures
noted below.  However, we'll have to watch arc-diff-spawned
tests for new failures, just in case.

This is by far the largest undecomposable patch of those
I've written for this task so far.  It is possible that
some subset of these changes accomplishes the same goal,
but once I managed to get a successful compilation, I have
only re-reviewed it once and did not try to shrink it.

Test Plan:
Without these changes, we would get the following 32 errors from gcc-4.9:
https://phabricator.fb.com/P19692642
With them, (and all of the other patches attached to the parent task,
all of fbcode compiles and passes its tests (modulo preexisting
failures and aborts).

Reviewed By: delong.j@fb.com

Subscribers: trunkagent, folly-diffs@

FB internal diff: D1773461

Tasks: 5941250

Signature: t1:1773461:1420821964:61635f3a2efc95e8d4457c36e7a5ee3a0a50df23

Summary:
First step of moving futures out of wangle into folly

Namespace change will be another diff

This was just a straight codemod of "wangle/futures" to "futures"

Test Plan: wait for contbuild

Reviewed By: davejwatson@fb.com

Subscribers: trunkagent, fbcode-common-diffs@, chaoyc, search-fbcode-diffs@, lars, ruibalp, hero-diffs@, zeus-diffs@, vikas, mcduff, hitesh, cold-storage-diffs@, unicorn-diffs@, ldbrandy, targeting-diff-backend@, netego-diffs@, fugalh, adamsyta, atlas2-eng@, alandau, apollo-diffs@, bmatheny, adityab, everstore-dev@, zhuohuang, sweeney, mwa, jgehring, prometheus-diffs@, smarlow, akr, bnitka, jcoens, zhguo, jying, darshan, apodsiadlo, alikhtarov, fuegen, dzhulgakov, alihussains, jeremyfein, mshneer, folly-diffs@, wch, lins, tingy, maxwellsayles, hannesr

FB internal diff: D1772041

Tasks: 5960242

Signature: t1:1772041:1420739169:36126b1264c5d1747d241921d02b13e306c73fe1

Summary:
* folly/Bits.h (BitIterator) [bitOffset_]: Change type of this
member from ssize_t to "unsigned int".
(bitsPerBlock): Change return type from size_t to "unsigned int".
These changes avoid some -Wsign-compare-highlighted issues, e.g.,
folly/Bits.h:456:18: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]

Test Plan:
Run this and note there are fewer errors than before:
fbconfig --platform-all=gcc-4.9-glibc-2.20 -r folly && fbmake dbgo

I've also run "fbmake runtests", and it failed precisely the way it does
without this patch.

Reviewed By: andrei.alexandrescu@fb.com

Subscribers: trunkagent, net-systems@, folly-diffs@

FB internal diff: D1770613

Tasks: 5941250

Signature: t1:1770613:1420757397:7ee7e5de500c8991af2597a6245d12d8f286b4b7

Summary:
With the upgrade to gcc-4.9 fbcode's default is to enable
-Wsign-compare by default.  That exposes nontrivial technical debt.
This is part of that clean-up.  Some of these changes fix the problem
where there's an "int" for-loop index, yet an unsigned limit.
The fix is to use an unsigned type when the limit is also unsigned.
I usually choose size_t because of the general recommendation (when
writing portable code) to avoid size-tied types like uint32_t and
uint64_t unless you have a very good reason to require them.

Test Plan:
Run this and note there are fewer errors than before:
fbconfig --platform-all=gcc-4.9-glibc-2.20 tao/server && fbmake dbgo

Also, run this, compiling and running tests with gcc-4.8.1.
Verify that there are no more failures than without this patch:
fbmake opt -k && fbmake runtests_opt
Here's the tail of that process, (same with and without the patch):
Summary (total time 47.45s):
PASS: 1949
FAIL: 1
SKIP: 0
FATAL: 9
TIMEOUT: 0

Reviewed By: hans@fb.com

Subscribers: trunkagent, fugalh, njormrod, folly-diffs@

FB internal diff: D1766722

Tasks: 5941250

Signature: t1:1766722:1420762240:a8545648ddb4fd0b2adf0d3147a84409c0f706a8

Summary: Apparently there is some dispute about the correct thing for `snprintf(buf, len, "bogus%", "foo")` to return. OSX says 5, Linux says -1. The code in `folly/String.cpp` depends on -1 to throw the exception this test was expecting.

Test Plan: make check on OSX

Reviewed By: chip@fb.com

Subscribers: exa, folly-diffs@

FB internal diff: D1770970

Tasks: 5936226

Signature: t1:1770970:1420680750:bafae2aa8327a52013e68af64a163323244ca03b

Summary:
This switches from gcc-4.9 provided by Homebrew to the default g++ (clang) from Yosemite.

$ g++ --version
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 6.0 (clang-600.0.51) (based on LLVM 3.5svn)
Target: x86_64-apple-darwin14.0.0
Thread model: posix

Absolute path for double-conversion, so make in `test/` works.

gtest-1.7.0 (Using 1.6.0 causes compilation errors in Yosemite)

Various portability fixes.

Enhancements/fixes to `configure.ac` and associated source code for better portability.

Test Plan:
It builds and runs (yay)
Two tests fail, not sure whether that's specific to osx. Will investigate and make any fixes in a follow-up diff

Reviewed By: pgriess@fb.com

Subscribers: trunkagent, folly-diffs@, exa

FB internal diff: D1768669

Tasks: 5936226

Signature: t1:1768669:1420728580:dd6919c21e0edf30788e523b16e3a5b923e2d7f0

Summary:
Default Yosemite clang has no `std::_Hash_impl`, which is an internal implementation detail anyway.

@davejwatson you might have a different suggestion about how to implement this without that function, or how to test if it exists and do this only if it doesn't. This is probably not the most efficient approach, since it copies the string.

Test Plan:
builds
inspection
fbgs doesn't turn up many results (only recent wangle ssl code really) so I don't think this will be a big perf regression if we just go with it. But if I'm wrong, we can gate it on `#if __APPLE__` or something.

Reviewed By: davejwatson@fb.com

Subscribers: folly-diffs@, fugalh, exa, davejwatson

FB internal diff: D1767052

Signature: t1:1767052:1420738784:e219ebff7aec8682b24c15a03b47077e1559c1ab

Summary: I got obliged into this one :o).

Test Plan: runtests

Reviewed By: meyering@fb.com

Subscribers: njormrod, folly-diffs@

FB internal diff: D1772328

Signature: t1:1772328:1420744114:2b81e46d77800d247293cb667bbef86e9d6d4755

Summary:
* folly/stats/Histogram-defs.h (HistogramBuckets): Take the unusual
approach of converting "numBuckets" to signed, because we cannot
cast "max-min" (a known positive value) to an unsigned type --
we don't have an unsigned variant of ValueType.
This avoids the following error from gcc-4.9:

folly/stats/Histogram-defs.h:41:31: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]

Test Plan:
Run this and note there are fewer errors than before:
fbconfig --platform-all=gcc-4.9-glibc-2.20 -r folly && fbmake dbgo

Reviewed By: ldbrandy@fb.com

Subscribers: trunkagent, net-systems@, folly-diffs@

FB internal diff: D1770129

Tasks: 5941250

Signature: t1:1770129:1420745311:c447e59f1730abafdf0b962e70f0886ae1d48db1

Summary:
* folly/detail/FileUtilDetail.h (wrapvFull): Change type of result
variable from ssize_t to size_t: this required changing r == -1 to
r == (size_t)-1.

Test Plan:
Run this and note there are fewer errors than before:
fbconfig --platform-all=gcc-4.9-glibc-2.20 -r folly && fbmake dbgo
Also run fbmake runtests, and confirm that the results are
the same with and without this change.

Reviewed By: lucian@fb.com

Subscribers: folly-diffs@

FB internal diff: D1772171

Tasks: 5941250

Signature: t1:1772171:1420743142:1f9e02006e2d77a0c9451bae7965fb28617d95d6

Summary:
* folly/wangle/futures/Future-inl.h (whenAll): Do not compare
signed (std::distance) with unsigned(size_t): add an assertion
to eliminate the possibility of negative, then assign to a new
size_t "n".

Test Plan:
Run this and note there are fewer errors than before:
fbconfig --platform-all=gcc-4.9-glibc-2.20 -r folly && fbmake dbgo

Reviewed By: jsedgwick@fb.com

Subscribers: trunkagent, fugalh, folly-diffs@

FB internal diff: D1770668

Tasks: 5941250

Signature: t1:1770668:1420736965:fc722657a2ec523052fd96c33d65d5ca24aae61c

Summary:
* folly/FBString.h (operator>>): Since istream.width() is signed,
handle the case of a negative width. This avoids risk that "n"
will be less than 0 when compared against unsigned "extracted".
However, to suppress the following warning, we must also explicitly
convert "n" to size_t before comparing:

folly/FBString.h:2326:22: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]

Test Plan:
Run this and note there are fewer errors than before:
fbconfig --platform-all=gcc-4.9-glibc-2.20 -r folly && fbmake dbgo

Reviewed By: andrei.alexandrescu@fb.com

Subscribers: trunkagent, net-systems@, njormrod, folly-diffs@

FB internal diff: D1770460

Tasks: 5941250

Signature: t1:1770460:1420679684:b262eb31e6511b6311bebf0fbc29099471648b36

Summary: as discussed in another diff, this might help with NRVO

Test Plan: unit

Reviewed By: hans@fb.com

Subscribers: trunkagent, fugalh, folly-diffs@

FB internal diff: D1764921

Signature: t1:1764921:1420677311:c6b63d7bf04c0e17283117b3edef798c288e5fbb

Summary: as above, fixes builds

Test Plan: compiled thrift + mcrouter

Reviewed By: seanc@fb.com

Subscribers: seanc, fugalh, folly-diffs@

FB internal diff: D1771910

Signature: t1:1771910:1420733490:7f33e57a5853395cab786e5d35d4c15c75a15c5a

Summary:
One header at a time, starting with the small fry

I'm allowed to drink while I do this right? Good, because I don't think I ever had a choice.

Test Plan: generated doxygen and looked decent http://home.fburl.com/~jsedgwick/html/classfolly_1_1wangle_1_1Try.html

Reviewed By: davejwatson@fb.com

Subscribers: trunkagent, fugalh, njormrod, folly-diffs@

FB internal diff: D1677730

Tasks: 5480262

Signature: t1:1677730:1415899240:bdd03569a82be1c8def8c13786eae39b4a2a2f94

Summary:
integrate exception_wrapper everywhere, and deprecate public methods that take ptrs directly to discourage their use
note that this will break for throwing non-exceptions, which is probably fine

this change opens the door to interesting optimizations for those interested, e.g. Future::then<Exn1, Exn2>(/* func throwing Exn1 and Exn2 */) that autowraps the given types into the resultant future

new benchmark:
```
throwAndCatch                                               23.69us   42.21K
throwAndCatchWrapped                             119.53%    19.82us   50.45K
throwWrappedAndCatchWrapped                      350.16%     6.77us  147.80K
```

Test Plan: existing unit tests, suspected potential perf wins confirmed by benchmark, will wait for windtunnel to see other wins/regressions

Reviewed By: hans@fb.com

Subscribers: search-fbcode-diffs@, apodsiadlo, alikhtarov, andrii, trunkagent, fugalh, njormrod, folly-diffs@, bmatheny

FB internal diff: D1644912

Signature: t1:1644912:1420731849:3dc658dc03bfd6e75d61158808c7dad96092ecfb

Summary:
* folly/String-inl.h (humanify): Count with a signed type.
Otherwise, gcc-4.9 fails with e.g.,
folly/String-inl.h:596:33: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
folly/String-inl.h:601:32: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]

Test Plan:
Run this and note there are fewer errors than before:
fbconfig --platform-all=gcc-4.9-glibc-2.20 -r folly && fbmake dbgo

Reviewed By: philipp@fb.com

Subscribers: trunkagent, folly-diffs@

FB internal diff: D1770451

Tasks: 5941250

Signature: t1:1770451:1420704354:c841ca453a5586fbf474535ca26cef17f95427dd

Summary:
* folly/AtomicHashArray.h (numEntries_, numPendingEntries_):
Use an unsigned type for each of these.  They count things, can
never go below 0, and are compared to unsigned values.
Otherwise, gcc-4.9 would emit this:
folly/AtomicHashArray-inl.h:153:38: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]

Test Plan:
Run this and note there are fewer errors than before:
fbconfig --platform-all=gcc-4.9-glibc-2.20 -r folly && fbmake dbgo

Reviewed By: philipp@fb.com

Subscribers: trunkagent, folly-diffs@

FB internal diff: D1770695

Tasks: 5941250

Signature: t1:1770695:1420683354:bfa4775bc2f8aab74e34772308a5c8b1779243b8

Summary:
* folly/AtomicHashMap-inl.h (insertInternal): Do not declare
nextMapIdx to be signed ("int"), since we compare it against
variables of unsigned type.  Otherwise, gcc-4.9 would give this
diagnostic:
folly/AtomicHashMap-inl.h:99:18: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
complaining about this comparison:
if (nextMapIdx >= kNumSubMaps_ ||

Test Plan:
Run this and note there are fewer errors than before:
fbconfig --platform-all=gcc-4.9-glibc-2.20 -r folly && fbmake dbgo

Reviewed By: philipp@fb.com

Subscribers: folly-diffs@

FB internal diff: D1770683

Tasks: 5941250

Signature: t1:1770683:1420683505:4452c7cb4f14f098be089601be906884036348ed

Summary:
Address multiple -Werror=sign-compare issues exposed when building
tao with gcc-4.9.
In most of these changes I've changed the type of the index in
a for-loop from int to size_t.  The important thing is to use
an unsigned type when the limit is also unsigned.  I choose size_t
because the general recommendation (when writing portable code)
to avoid size-tied types like uint32_t and uint64_t unless you
have a very good reason to require them.

Test Plan:
Run this and note there are fewer errors than before:
fbconfig --platform-all=gcc-4.9-glibc-2.20 tao/server && fbmake dbgo

Reviewed By: andrei.alexandrescu@fb.com

Subscribers: trunkagent, net-systems@, folly-diffs@

FB internal diff: D1766651

Tasks: 5941250

Signature: t1:1766651:1420594537:56ef53ca233e1649469db9570942c1d5dd47cf6d

Summary:
* folly/test/ForeachTest.cpp: Change a "1" to "1U", so it matches
the signedness of the size_t upper bound.
Otherwise, gcc-4.9 fails with e.g.,
folly/Foreach.h:194:16: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]

Test Plan:
Run this and note there are fewer errors than before:
fbconfig --platform-all=gcc-4.9-glibc-2.20 -r folly && fbmake dbgo

Reviewed By: andrei.alexandrescu@fb.com

Subscribers: folly-diffs@

FB internal diff: D1770603

Tasks: 5941250

Signature: t1:1770603:1420679246:56ef62ac7fa4413a4ad6310c3381a12bdc59e64c