Summary:
Tweak the wording of a couple error messages to make them clearer.
Also disable the 'digraphs not supported' warning, as none of our supported compilers actually interpret digraphs in any of our supported build configurations.

Closes: https://github.com/facebook/folly/issues/706

Reviewed By: yfeldblum

Differential Revision: D6299715

fbshipit-source-id: 7c847ac859e082aea711f6751f626b4b43886da4

Summary:
When __NR_membarrier is defined (on newer kernels),
we don't define the constants, but also by default
don't include the membarrier header to define the necessary constants.
Therefore split the definition of the syscall value and
the constants used with it, to ensure both are defined.

Reviewed By: yfeldblum

Differential Revision: D6292178

fbshipit-source-id: 31ba9d4a698a4f5e14ae34de0acf8f851d75527d

Summary:
With gcc 7.2 we get the warning:
  folly/io/async/DelayedDestructionBase.h:252:20:
  error: parameter ‘right’ set but not used [-Werror=unused-but-set-parameter]
     std::nullptr_t right) {
                    ^~~~~
I presume this is due to the implicit conversion, hence the named parameter is
never assigned.  Instead we use an explicit nullptr.

Reviewed By: yfeldblum

Differential Revision: D6279302

fbshipit-source-id: ed449601b0410c178777f20e82ed09d9097bd024

Summary:
The current folly::once_flag is not compatible with folly fibers
and when using it with fibers is inefficient and also cause deadlocks.

This diff makes the once flag's mutex be a templatable paramter
and overrides it in fibers library with a fiber compatible mtuex.

Reviewed By: yfeldblum

Differential Revision: D6288508

fbshipit-source-id: 6f82e1794d1f417f8d267061f1702a26a7b4ff12

Summary:
[Folly] Add `makeSemiFuture` declarations to `helpers.h`.

For consistency with the `makeFuture` declarations that are also there. Definitions for both are found in `Future-inl.h`.

Reviewed By: LeeHowes

Differential Revision: D6281826

fbshipit-source-id: 4b22dd9086d05dbdebba358c6f569a772017949a

Summary:
Some older versions of GCC/glibc/etc do not have the
std::is_trivially*_constructible or std::is_trivially*_assignable traits.

Reviewed By: yfeldblum

Differential Revision: D6285887

fbshipit-source-id: 1eb4ae4f899dc1f528321f9f087390291687aca3

Summary: Remove the zerocopy write threshold support since it is a little bit confusing

Reviewed By: djwatson

Differential Revision: D6256854

fbshipit-source-id: 1c992f93d7b04c4ede2fbefebde7a7ae89de3764

Summary:
Currently `folly::symbolizer`'s `getDefinitionByAddress` and `getSymbolByName` only parses `STT_OBJECT` and `STT_FUNC`. There are some standar library functions that uses the GNU indirect function feature that would have been missed:

  ==== For libpthread-2.23.so:
  ====== Symbol system Addr 119d0 Size 8 is a STT_GNU_IFUNC
  ====== Symbol siglongjmp Addr 10700 Size 8 is a STT_GNU_IFUNC
  ====== Symbol longjmp Addr 10700 Size 8 is a STT_GNU_IFUNC
  ====== Symbol __vfork Addr 10af0 Size 8 is a STT_GNU_IFUNC
  ====== Symbol vfork Addr 10af0 Size 8 is a STT_GNU_IFUNC
  ====== Symbol system_ifunc Addr 119d0 Size 8 is a STT_GNU_IFUNC
  ====== Symbol longjmp_ifunc Addr 10700 Size 8 is a STT_GNU_IFUNC
  ====== Symbol vfork_ifunc Addr 10af0 Size 8 is a STT_GNU_IFUNC
  ====== Symbol siglongjmp_ifunc Addr 10700 Size 8 is a STT_GNU_IFUNC
  ====== Symbol __vfork_ifunc Addr 10af0 Size 8 is a STT_GNU_IFUNC
  ====== Symbol __vfork@GLIBC_2.2.5 Addr 10af0 Size 8 is a STT_GNU_IFUNC
  ====== Symbol siglongjmp@GLIBC_2.2.5 Addr 10700 Size 8 is a STT_GNU_IFUNC
  ====== Symbol vfork@GLIBC_2.2.5 Addr 10af0 Size 8 is a STT_GNU_IFUNC
  ====== Symbol system@GLIBC_2.2.5 Addr 119d0 Size 8 is a STT_GNU_IFUNC
  ====== Symbol longjmp@GLIBC_2.2.5 Addr 10700 Size 8 is a STT_GNU_IFUNC

  ==== For libc-2.23.so:
  ====== Symbol __gettimeofday Addr c05e0 Size a8 is a STT_GNU_IFUNC
  ====== Symbol strcpy Addr 8e150 Size 35 is a STT_GNU_IFUNC
  ====== Symbol wmemcmp Addr afb50 Size 37 is a STT_GNU_IFUNC
  ====== Symbol strncmp Addr 8eb30 Size 41 is a STT_GNU_IFUNC
  ====== Symbol stpncpy Addr 929f0 Size 35 is a STT_GNU_IFUNC
  ====== Symbol __mempcpy_chk Addr 11cec0 Size 68 is a STT_GNU_IFUNC
  ====== Symbol strncpy Addr 903d0 Size 35 is a STT_GNU_IFUNC
  ====== Symbol time Addr c0500 Size a8 is a STT_GNU_IFUNC
  ====== Symbol strpbrk Addr 90700 Size 22 is a STT_GNU_IFUNC
  ====== Symbol strspn Addr 90a80 Size 22 is a STT_GNU_IFUNC
  ====== Symbol __stpncpy Addr 929f0 Size 35 is a STT_GNU_IFUNC
  ====== Symbol __strcasecmp Addr 92a80 Size 54 is a STT_GNU_IFUNC
  ====== Symbol memset Addr 92230 Size 41 is a STT_GNU_IFUNC
  ====== Symbol strstr Addr 916b0 Size 21 is a STT_GNU_IFUNC
  ====== Symbol strcspn Addr 8e270 Size 22 is a STT_GNU_IFUNC
  ====== Symbol memcmp Addr 91c40 Size 37 is a STT_GNU_IFUNC
  ====== Symbol mempcpy Addr 923b0 Size 68 is a STT_GNU_IFUNC
  And 80 more...
This Diff adds parsing for `STT_GNU_IFUNC` symbols as well

Reviewed By: yfeldblum

Differential Revision: D6282727

fbshipit-source-id: 71b7c44831e4ddfdccf1e794cb86e049e14227bc

Summary:
When using `folly::symbolizer`, it's very often that we want to use `iterateSectionsWithType` iterate through sections of a few types using the same callback. Current approach would require iterating the section header multiple times.

This Diff add `iterateSectionsWithTypes`, which is basically just `iterateSectionsWithType` but accepts multiple section types.

It is very similar to D6279651. However, in this Diff we did not change implementation of `getDefinitionByAddress` and `getSymbolByName`, since going through `.dynsym` separately would improve the efficiency of single-address or single-symbol lookup. However, for the use cases that we want to iterate through all symbols of an ELF file, this new interface would be useful.

Reviewed By: anakryiko, yfeldblum

Differential Revision: D6281449

fbshipit-source-id: f9afe0a0e95d9fafcd041014abad8ca86d1a882f

Summary:
[Folly] Fix `folly/test/Makefile.am`.

Closes #709.

Reviewed By: meyering

Differential Revision: D6282009

fbshipit-source-id: 0f2a992e92d4b94a535f29341920c9f2959819d7

Summary:
When using `folly::symbolizer`, it's very often that we want to use `iterateSymbolsWithType` iterate through symbols of a few types using the same callback. Current approach would require iterating the section multiple times.

This Diff adds `iterateSymbolsWithTypes`, which is basically just `iterateSymbolsWithType` but accepts symbol types.

This Diff also updated implementation of `getDefinitionByAddress` and `getSymbolByName` which currently does two iterations for `STT_OBJECT` and `STT_FUNC`.

Reviewed By: yfeldblum

Differential Revision: D6279651

fbshipit-source-id: a661dd15f18e4f2f63dbcca615f5a86d92e528ea

Summary:
[Folly] In `SemiFuture` members, fix `DCHECK` of pointer types.

Use `nullptr !=` to avoid ` error: ISO C++ forbids comparison between pointer and integer`.

Closes #708.

Reviewed By: Orvid

Differential Revision: D6277832

fbshipit-source-id: 8f65065d5347c6ac407b99cb780c38935e901362

Summary:
Testing indicates that GCC ignores the cold attribute when the function
is available for inlining. Because Unexpected is a template class we
can't make the constructors non-inline, but we can make it derive from a
class with a cold constructor, which has the effect of making all the
Unexpected constructors implicitly cold.

Reviewed By: yfeldblum

Differential Revision: D6261013

fbshipit-source-id: 482e49253d5b104742018133c53fb60279dd9f9b

Summary: Because every other exception is already marked as public.

Reviewed By: yfeldblum

Differential Revision: D6275414

fbshipit-source-id: 8e1fc4ceafedbdb44733ab57aecb6050c4160994

Summary:
gflags and glog require some compile definitions when linking statically
/cc Orvid
Closes https://github.com/facebook/folly/pull/693

Reviewed By: yfeldblum

Differential Revision: D6264382

Pulled By: Orvid

fbshipit-source-id: 60c8af429f10e778d9c313f40227892238829f63

Summary:
[Folly] Heterogeneous lookups for `sorted_vector` types.

When the `Compare` type has member type or alias `is_transparent`, enable template overloads of `count`, `find`, `lower_bound`, `upper_bound`, and `equal_range` on both `sorted_vector_set` and `sorted_vector_map`.

This is the protocol found in the equivalent `std::set` and `std::map` member functions.

> This overload only participates in overload resolution if the qualified-id `Compare::is_transparent` is valid and denotes a type. They allow calling this function without constructing an instance of `Key`.
>
> http://en.cppreference.com/w/cpp/container/set/count (same wording in all 10 cases)

Reviewed By: nbronson

Differential Revision: D6256989

fbshipit-source-id: a40a181453a019564e8f7674e1e07e241d5ab068

Summary: Use const_cast instead of implicitly dropping const modifier.

Reviewed By: reanimus

Differential Revision: D6269200

fbshipit-source-id: 61e1708c88a4139d3fdd9cf89f4ff778d0354bb2

Summary:
Include folly/Portability.h in GenerateFingerprintTables, so that
gflags namespace gets defined.

Reviewed By: yfeldblum

Differential Revision: D6265226

fbshipit-source-id: d509dc163564420151de7007ad4336d7e5ef9625

Summary:
Exposed by the latest clang:
```lang=bash
folly/test/FixedStringTest.cpp:52:36: error: unused variable 's' [-Werror,-Wunused-variable]
  constexpr folly::FixedString<42> s{"hello world"};
                                   ^
folly/gen/test/StringBenchmark.cpp:176:15: error: unused variable 'line' [-Werror,-Wunused-variable]
  StringPiece line(kLine);
              ^
```

Reviewed By: yfeldblum

Differential Revision: D6264853

fbshipit-source-id: 5cf4b0a8c99eaa31c2499746c70ddc49fdd73074

Summary:
It was broken, now it is fixed.
https://developercommunity.visualstudio.com/content/problem/145407/incorrect-c3520-within-noexcept-expression-in-alia.html

Reviewed By: yfeldblum

Differential Revision: D6254219

fbshipit-source-id: a03961db97d7ac211103655229c1ea703405826a

Summary:
AsyncFileWriter uses a separate thread to write messages to the file
descriptor.  This diff makes us call setThreadName() to set the name of this
thread to `log_writer`.

Reviewed By: bolinfest

Differential Revision: D6238229

fbshipit-source-id: 9c93d80e7ac989e03bc3160bb2f135d67e15c8be

Summary: Use the same trick as the values, so that non-copyable keys can be used in ConcurrentHashMap.

Reviewed By: yfeldblum

Differential Revision: D6252711

fbshipit-source-id: f0f168c4eb361d372bdfc3417f32222d66c11aaf

Summary:
While the returned iterators are always 'valid' and can be read and iterated from,
they may still be concurrently erased from the map.  Current erase(iter) has DCHECKS that assert we can always
erase an iterator, but it may have already been removed.

Reviewed By: davidtgoldblatt

Differential Revision: D6221382

fbshipit-source-id: 70b21f53e2fc3daa126df4fb60bc5d3ecb253c71

Summary: The `THROW` behavior of `LifoSemMPMCQueue` is unsafe when calling `join()`, because the queue may be full and `join()` will fail to enqueue the poisons. To work around this we can use `PriorityLifoSemMPMCQueue` and dedicate `LO_PRI` to the poisons, but there's no reason that the low priority queue should have the same size as the normal priority. Add a constructor to be able to specify different sizes.

Reviewed By: yfeldblum

Differential Revision: D6257017

fbshipit-source-id: c75f33c38fcdad646ba1499bcd434ab65711250c

Summary:
[Folly] `crange`, and `range` `const` overloads.

Instead of using universal reference for `range` overloads, bifurcate explicitly between `&` and `const&` overloads. The `&` overloads return `Range<T*>` while the `const&` overloads return `Range<T const*>`.

Add `crange` overloads, which may accept non-`const` arguments but will return `Range<T const*>` results anyway.

Reviewed By: ot

Differential Revision: D6242038

fbshipit-source-id: bc373c3288ea88792f04b49a372262d12204b586

Summary: [Folly] Move `folly/LifoSem.h` to `folly/synchronization/`.

Reviewed By: meyering

Differential Revision: D6245444

fbshipit-source-id: 14ffa012fa92b8c6aaf5900c930156894a492003

Summary: The Data field was not getting value-initialized, leading compilers to complain when value-initializing const folly::Function objects.

Reviewed By: yfeldblum, ot

Differential Revision: D6241712

fbshipit-source-id: 99ce7f6016f6e7d16b1cff7aa51b7bef53ec592d

Summary:
By marking the main constructors of `Unexpected` cold we are telling the compiler that we don't expect to execute them often. This can improve the locality and performance of the `Expected` branch, and reduce the code-size for the `Unexpected` branch.

The constructors we have marked cold here are only the ones used to originate an `Unexpected`. We don't mark the copy- move- or conversion-constructors as `cold` because they will typically be used in error-handling branches and it is not correct to say that they are colder than their surroundings in that case. Note that the entire error-handling branch is likely to be deduced to be cold because we told the compiler that it is likely that hasValue() is true and hasError() is false.

Because `makeUnexpected` unconditionally invokes one of these cold constructors it will inherit the property of being cold.

The GCC function attribute reference, which describes what `cold` means, is here: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes

Reviewed By: yfeldblum

Differential Revision: D6234305

fbshipit-source-id: 6876073e92ce54936ba7152175d76be653f5f463

Summary: [Folly] Move `folly/Functional.h` to `folly/lang/RValueReferenceWrapper.h`.

Reviewed By: Orvid

Differential Revision: D6242160

fbshipit-source-id: a8ec42106cfe0ea617c87d382694d5eb2f0f61a0

Summary:
[Folly] `constexpr_clamp`.

Like `std::clamp` (C++17).

Reviewed By: Orvid

Differential Revision: D6236825

fbshipit-source-id: 0f6c5dc9a955b148021ee6ed3e86201b53ae090c

Summary: Make SemiFuture throw if no executor provided to via because in that situation the deferred work will never run.

Reviewed By: yfeldblum

Differential Revision: D6233233

fbshipit-source-id: 43b642c46cc0be80b1f13c03bdaf20b8038acec2

Summary: [Folly] Move `folly/SafeAssert.h` to `folly/lang/`.

Reviewed By: Orvid

Differential Revision: D6230421

fbshipit-source-id: 0086cd6fedd4ce0e7a4d5302a41153ec1a502e74

Summary: Fix for function parameter order that shows up in opt build on later diff.

Reviewed By: andriigrynenko

Differential Revision: D6237125

fbshipit-source-id: fbb7be2c70b32203c658fc239cd74164e01fa1ca

Summary: Closes https://github.com/facebook/folly/pull/705

Reviewed By: yfeldblum

Differential Revision: D6234351

Pulled By: Orvid

fbshipit-source-id: e71bb3882c783a47ace4d08f134b2e450aaabb6b

Expose the zerocopy buf ID, change the AsyncSocket fd constructor to accept the id, Buff->Buf, make the cmsghdr methods private

Summary: Expose the zerocopy buf ID, change the AsyncScokey fd constructor to accept the id, Buff->Buf, make the cmsghdr methods private

Reviewed By: djwatson

Differential Revision: D6221324

fbshipit-source-id: d0fc4937adf6cf5790d11e406ffd3ec64c558b9c

Summary: Conversion check was lost in an earlier refactor. This meant that SemiFuture could be accidentally converted to Future through the value constructor. This should be disabled.

Reviewed By: yfeldblum

Differential Revision: D6214526

fbshipit-source-id: 3fc2d026ec6062b38b9500c8adf3eee12c0f2693

Summary: [Folly] Alias `std::launder` when it is available.

Reviewed By: Orvid

Differential Revision: D6221443

fbshipit-source-id: 33136a8744a39db01fb05513d5ed5476ea67559a

Summary: gcc-4.9 does not support features that Poly needs. Disable the tests on that platform.

Reviewed By: meyering

Differential Revision: D6211674

fbshipit-source-id: 289f029122a45b0f9ec740c62b1faaafb51dcab5

Summary: This only affects instruction ordering in GCC-compatible compilers to make the value-having branch preferred.

Reviewed By: davidtgoldblatt, nbronson, yfeldblum

Differential Revision: D6223188

fbshipit-source-id: 57c69b88eda7ee769912874921c45b47ec7a38de

Change kDefaultZeroCopyThreshold to 0 to avoid a regression and avoid a failure while running as not root

Summary:
Change kDefaultZeroCopyThreshold to 0 to avoid a regression when using a buffer chain that exceeds 32K but each buffer is small.
Change the benchmark to set it's own threshold. Also use calloc vs malloc (in the benchmark only) to get around some weird kernel interaction on non zero copy enabled systems - 2 back to back tests report very different results.

Reviewed By: djwatson

Differential Revision: D6112299

fbshipit-source-id: 3895d3ece2925c4626284ff364495708293edc3e