Summary:
- As of C++17, `std::string` contains a non-const `data()` member function.
  This is useful when working with C APIs that have `char*` output parameters.
- Implements P0272 for `FBString`:
  http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0272r1.html

Example of workaround without this:

```
  fbstring s{};
  some_api(&s.front());
```

- The expression `&s.front()` above causes undefined behavior since the string
  is empty.

- Add non-const public member function `data()` to `fbstring` which
  delegates to `fbstring_core`.
Pull Request resolved: https://github.com/facebook/folly/pull/1116

Reviewed By: Orvid

Differential Revision: D15213884

Pulled By: yfeldblum

fbshipit-source-id: f533542db0a7e34c09a622e5257d7c1e66ab75e2

Summary:
[Folly] `small_vector<T>::get_allocator()` for compatibility with other container types.

While `small_vector` is not actually parameterizable over the allocator types, compatibility with generic interfaces such as the presorted-ctor interfaces of `sorted_vector_set` and `sorted_vector_map` require `get_allocator`.

Reviewed By: vitaut

Differential Revision: D15194509

fbshipit-source-id: 3a7842d5640f8e95a09c4cd8e2a9ab6ffc4fe9ac

Summary: [Folly] container_type member alias for `sorted_vector_set` and `sorted_vector_map`, following the protocol from `std::queue`, `std::priority_queue`, and `std::stack` container adaptors.

Reviewed By: vitaut

Differential Revision: D15194108

fbshipit-source-id: 91332478c66779690f415d598b99274b8ee52df4

Summary: [Folly] `kGlibcxxVer`, from `_GLIBCXX_RELEASE` if available.

Differential Revision: D15209042

fbshipit-source-id: 077e94db623f33ebc3ec2cb93a5d7774d384a863

Summary: [Folly] Always `#include <bits/c++config.h>` if possible from `folly/portability/Config.h`. This is the libstdc++ (glibcxx) version/config/features header, so include it alongside the corresponding glibc version/config/features header.

Differential Revision: D15209040

fbshipit-source-id: 6f624283f58523d74317f3d998aa99c1c50ee2b3

Summary:
Split validateRecord to allow validating header and data separately. This is
useful when the header is used while storing records on storage devices.
Validating header alone before validating the record helps avoiding unnecessary
device reads. It also helps avoiding unnecessary memory allocations while trying to read invalid dataLength bytes present in an invalid header.

Reviewed By: yfeldblum

Differential Revision: D15184763

fbshipit-source-id: e1f008df82cf2d040322b8d62135ea2b5e0dcc0e

Summary: [Folly] Use `noexcept` in `IOBuf` v.s. reimplementing it via explicit `catch` and `abort`, with the intended side-effect of adding support for `-fno-exceptions`.

Reviewed By: simpkins

Differential Revision: D15208427

fbshipit-source-id: bcf9d7b0f1a556e43d996c84b1df43ff891da974

Differential Revision:
D15073229

Original commit changeset: 417a1f4e42d0

fbshipit-source-id: 689b010627482e9a05f3dd34e89baae485875025

Summary:
This is useful especially on Windows where the up-to-date
checks for the dependencies take a long time.

The idea is that you might run this to start:

```
$ getdeps.py build eden
```

and then while in the edit/debug/build iteration cycle:

```
$ getdeps.py build --no-deps eden
```

Reviewed By: pkaush

Differential Revision: D15200352

fbshipit-source-id: 086f2f49db967ef4d1914a69fa80067104d79136

Summary:
Previously, we were using autoconf to build sqlite,
but that isn't available on Windows.  Instead, here's a builder
that generates a little cmake configuration for building and
installing sqlite.

Using cmake for this means that we can test the same builder
on all platforms that need to pull in sqlite.

Reviewed By: simpkins

Differential Revision: D15179387

fbshipit-source-id: fccf969182565982bd5be55545a2d2625aa99124

Summary:
When running in FB infra, prefer to download from our local LFS
server rather than going out to the internet.

Fall back to a normal internet download if the LFS get fails for some reason.

Upload to LFS after successfully verifying the hash for the downloaded archive.

Add a subcommand that performs a fetch for all possible platforms so that it
is easier to ensure that the lfs-pointers file is up to date.

Reviewed By: simpkins

Differential Revision: D14978660

fbshipit-source-id: 240fc32fc7003d1e06c88b80d85054dae36e2f31

Summary:
In order to pull in the treemanifest and other libraries
from our mercurial repo, add a manifest file for it, and then
adjust the logic in our cmake module to look for it.

The fb-mercurial manifest just copies the source tree to the
installation dir.  In the future, we could teach it to invoke
the build for real.

Reviewed By: simpkins

Differential Revision: D14969806

fbshipit-source-id: cb270c5003a1c134eeea92c7481a84938f1c5957

Summary:
This prints out the installation or source prefix for a given project.
This is useful in eg: packaging scripts to figure out where they can
find the built artifacts.

Reviewed By: simpkins

Differential Revision: D14967378

fbshipit-source-id: 7e1b5de2ca7219af24cfb07b4b42de22aa410469

Summary:
If `testpilot` is available, generate a buck compatible json file describing the available test binaries and feed that to testpilot to have it run the tests.

A later (yet to be written) diff will be able to pass appropriate flags down to testpilot in continuous runs and that will allow testpilot to auto-disable and file tasks for tests in the opensource builds.

Reviewed By: simpkins

Differential Revision: D14766856

fbshipit-source-id: 4e144ff18f6788cf5e830d29788eabd2dbbae46a

Summary:
The loader makes it possible to monkey patch the functions
that are responsible for loading manifests.  It is intended to be use
in tests that are run in bucks sandboxed environment and that don't
have direct access to the manifest files on disk.

Reviewed By: simpkins

Differential Revision: D14781326

fbshipit-source-id: 18f69f8ce5768dc605b1a9388a80b7b7b9ffe0f4

Summary:
previously, a relatively lame hash was computed to use
for the build directory based on some hash of the source directory.
That was good enough to get things off the ground, but in the
interest of being able to cache the build outputs and safely
invalidate them we need a slightly more rigorous implementation.

This diff computes a hash based on the manifest contents and
relevant environmental factors.

The hash is used to name the build directory which will ultimately
be cached eg: using the travis/appveyor cache directory configuration
and some other means for the FB internal CI.

The hash needs to be sufficient that we change the hash when
the manifests change.  We can tolerate a false positive change
in hash (it just means that a build will take longer), but
cannot tolerate a false negative (which would result in an
incorrect build).

Reviewed By: simpkins

Differential Revision: D14710332

fbshipit-source-id: ebc2e74eafc6f3305d4412a82195bc9fb9dfa615

Summary:
This command schedules a facebook specific sandcastle job for the current
commit in your repo for each of the platforms we have support for in
sandcastle.

You can use `--dry-run` to have it print out the job specs.

To support this, I've moved around some of the support utilities
to make it easier to import them.

Reviewed By: simpkins

Differential Revision: D14710330

fbshipit-source-id: fb1e2a2ce78e52894291159514977da97028b37f

Summary:
Adds a `test` subcommand that runs the tests for project.
We're mostly interested in the 1st party facebook projects for this.

The `sandcastle` flow will run the `test` subcommand just for the "leaf" project--the one named on the command line.

Reviewed By: simpkins

Differential Revision: D14710331

fbshipit-source-id: 7d04a46cfd723894d61018de2f230140b52285ac

Summary:
This cleans up the scratch dir, removing everything except
for downloaded tarballs.

Reviewed By: simpkins

Differential Revision: D14781328

fbshipit-source-id: 9304e44a268cf7996c5e572a2eca219aefbf4b46

Summary:
This fixes a TODO; in our CI environment we want to use the
real shipit, so we'll use this flag to make that happen.

Reviewed By: simpkins

Differential Revision: D14695576

fbshipit-source-id: 64ee72c210e2472d295dcbd39c86549273b68452

Summary:
This makes it possible to disable eden (and thus thrift) support.

I've defaulted this to off so that we don't break the existing
watchman CI.

Reviewed By: simpkins, strager

Differential Revision: D14726767

fbshipit-source-id: 0f4d0597d901a91850f1ba6d71609c059c064c22

Summary:
adds the command that is used to drive a build.

The dependencies of the named project are computed using
the same mechanism behind the `list-deps` subcommand.
If a manifest specifies that it uses the `cmake` builder then
a dependency on `cmake` is synthesized so that we can download
a recent version of cmake ahead of time.

The build command uses the fetcher to update the src and then
executes the builder.

Reviewed By: simpkins

Differential Revision: D14691011

fbshipit-source-id: 31ae59614651ef021a9505e89c13b5717b440071

Summary:
this could do with a better name; the NopBuilder doesn't actually
build anything, but instead copies some files to the destination location.

This is used together with eg: cmake to install pre-built binaries downloaded
from a tarball.

Reviewed By: simpkins

Differential Revision: D14691015

fbshipit-source-id: a938e977aa4ec5a664bdb8085ff708319a204594

Summary:
the boost builder knows how to perform the non-standard
configure and build for boost.

Ideally we'd just build this statically and be happy but there are
some nuances I've observed while building on different platforms:

* One of our projects (thrift or wangle) explicitly requests static
  boost linkage for reasons unspecified
* on darwin the install_name is broken when building dynamic libs

For the sake of expediency in getting getdeps up and running, the
solution for the moment is to build static on posix systems and
build both static and shared on windows systems.

Reviewed By: simpkins

Differential Revision: D14691009

fbshipit-source-id: 634770a6f53c3ada42d1877cc6c3dacc6eed7d18

Summary:
the openssl builder knows how to perform the non-standard
configuration and build steps to build openssl.

On Linux systems the manifests for our projects don't mention
openssl, causing them to pick up the system openssl.

On Mac, apple don't ship openssl headers so we need to build our own.
On Windows there is no standard openssl installation so we also need
to build our own.

As a result, this builder only works on windows and mac.

Reviewed By: simpkins

Differential Revision: D14691010

fbshipit-source-id: 9f8979f9eaeb5209c290cf4f43c97c0cb43d13a2

Summary:
this builder is used to bootstrap the ninja build tool.

On Windows and mac the manifest for ninja is set to download a pre-built executable.
While pre-built executables are available for linux they aren't portable enough
for our purposes so we need to be able to build it for ourselves.

Reviewed By: simpkins

Differential Revision: D14690992

fbshipit-source-id: b60fd02ad04f58dc7c2931280341791270609737

Summary:
the cmake builder knows how to use cmake to configure a build
for (preferably) and out-of-src build.  The `cmake.defines` section of
the manifest is used to pass `-Dkey=value` options to the cmake configure
command line.

We prefer to use `ninja` to execute the build so that we can use more
cores than 1 on Windows and just for consistency across platforms
with mac and linux.

Reviewed By: simpkins

Differential Revision: D14690998

fbshipit-source-id: 8102e8b4a47da515ca001772788ed0e5f2645ad7

Summary:
the autoconf builder performs an out-of-source build using
the autoconf suite to configure the build rules.

The `autoconf.args` section from the manifest is passed to the `./configure`
command line.

If an `autogen.sh` script is present then it will be used to regenerate
a missing `configure` script, otherwise we'll try `autoreconf`.

Reviewed By: simpkins

Differential Revision: D14691002

fbshipit-source-id: ab8cceafb833dab513d5a50c65f4c895a4f40047

Summary:
the make builder runs `make` in the source directory.
The `make.args` section from the manifest is passed as arguments
to the `make` invocation.

Reviewed By: simpkins

Differential Revision: D14690996

fbshipit-source-id: 180d657ad05f0c0266a8c1d30979d8d1473958c9

Summary:
a builder knows how to build and install a project.

Later diffs add concrete implementations of the BuilderBase

Reviewed By: simpkins

Differential Revision: D14691018

fbshipit-source-id: 89b14614b5160353cd7e59f27037afcdf6229eb7

Summary:
While the command isn't necessarily super useful
on its own, it does show that the plumbing for walking the
deps is functioning, and that is important when it comes
to building.

The output lists the projects in the order that they
would be built.

The `fetch` command has been augmented to add a `--recursive`
flag that uses the same mechanism to recursively fetch
the dependencies.

Reviewed By: simpkins

Differential Revision: D14691004

fbshipit-source-id: b00bf6ad4742f8bb0a70698f71a5fe03d6a1f453

Summary:
Adds a command that can be used to trigger a fetch for a project

```
$  ./opensource/fbcode_builder/getdeps.py fetch zstd
Cloning https://github.com/facebook/zstd.git...
 ---
+ git clone --depth=100 https://github.com/facebook/zstd.git /data/users/wez/scratch/dataZusersZwezZfbsource/fbcode_builder_getdeps/repos/github.com-facebook-zstd.git
Cloning into '/data/users/wez/scratch/dataZusersZwezZfbsource/fbcode_builder_getdeps/repos/github.com-facebook-zstd.git'...
remote: Enumerating objects: 3816, done.
remote: Counting objects: 100% (3816/3816), done.
remote: Compressing objects: 100% (1415/1415), done.
remote: Total 3816 (delta 2556), reused 3312 (delta 2288), pack-reused 0
Receiving objects: 100% (3816/3816), 2.93 MiB | 9.59 MiB/s, done.
Resolving deltas: 100% (2556/2556), done.
Updating /data/users/wez/scratch/dataZusersZwezZfbsource/fbcode_builder_getdeps/repos/github.com-facebook-zstd.git -> v1.3.8
 ---
+ git -C /data/users/wez/scratch/dataZusersZwezZfbsource/fbcode_builder_getdeps/repos/github.com-facebook-zstd.git fetch origin v1.3.8
From https://github.com/facebook/zstd
 * tag               v1.3.8     -> FETCH_HEAD
 ---
+ git -C /data/users/wez/scratch/dataZusersZwezZfbsource/fbcode_builder_getdeps/repos/github.com-facebook-zstd.git checkout FETCH_HEAD
Note: checking out 'FETCH_HEAD'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by performing another checkout.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -b with the checkout command again. Example:

  git checkout -b <new-branch-name>

HEAD is now at 470344d Merge pull request #1479 from facebook/visualTest
 ---
+ git -C /data/users/wez/scratch/dataZusersZwezZfbsource/fbcode_builder_getdeps/repos/github.com-facebook-zstd.git submodule update --init
```

Reviewed By: simpkins

Differential Revision: D14691008

fbshipit-source-id: 3afa391360518a08ebd6ff97f5b8b4993f10c4e8

Summary:
This fetcher knows how to transform a 1st party project
from fbsource into approximately the same shape as ShipIt produces
for the github repo mirrors.  It does this by reading shipit
mapping information from the manifest file for the project.

Since this fetcher uses data in the manifest and is implemented
directly in the getdeps codebase, it is suitable for iterating
on the opensource builds directly out of fbsource on both devservers
and laptops inside FB.

Reviewed By: simpkins

Differential Revision: D14691012

fbshipit-source-id: 05f68a7be64a2e465937b24b8825d25d3348ed13

Summary:
This fetcher knows how to take a 1st party FB project
from fbsource and transform it to the same shape as our github
repos using ShipIt.  The transformation creates a transformed
mirror of the code in scratch space (rather than mutating fbsource
directly).

This can only be used in environments where shipit is available.
A later diff implements an alternative that works in more environments.

Reviewed By: simpkins

Differential Revision: D14691013

fbshipit-source-id: 539e307755c9fc0a098a235868ab622652061494

Summary:
this fetcher knows how to download a URL that references
an archive and extract the sources from it.  Compressed tarballs
and zipfiles are supported.

Reviewed By: simpkins

Differential Revision: D14690994

fbshipit-source-id: ffbbd1d9479b0d5aa3e5cd13fe11a560e9d01c2a

Summary: this fetcher knows how to check out sources via git.

Reviewed By: simpkins

Differential Revision: D14691000

fbshipit-source-id: 60f1ffbfed7b32a019aef6aa70ae0903f2782451

Summary:
Fetchers are used to fetch a source directory from a
source defined in a manifest file.

More details can be found in comments on the various methods.

The Manifest class offers a create_fetcher method for constructing
an appropriate fetcher.  This is just a stub in this commit, but
will expand over the course of the next few diffs as concrete
fetcher instances are added.

Reviewed By: simpkins

Differential Revision: D14691001

fbshipit-source-id: 8c9038eacae3345e9403d5d1304bf979a9ee1555

Summary:
The build options class contains some environmental and
build related information that will be passed down to fetcher
and builder objects that will be introduced in later diffs.

Reviewed By: simpkins

Differential Revision: D14691007

fbshipit-source-id: e8fe7322f590667ac28a5a3925a072056df0b3e3

Summary:
This will feed into the manifest context for system
dependent manifest sections.  This is essentially the same
code borrowed from the watchman and eden getdeps.py.

Reviewed By: simpkins

Differential Revision: D14690997

fbshipit-source-id: 3d3ae146237a2cd49609aaa2bd0e785ebe21f02c

Summary:
this module adds some functions that help with copying
directory trees.  The copytree function is aware of eden and will
issue a prefetch prior to walking the directory.

Reviewed By: simpkins

Differential Revision: D14691006

fbshipit-source-id: 079bf850756f61aca17978453d07bc73b2f91788