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247 lines
7.1 KiB
Markdown
247 lines
7.1 KiB
Markdown
Folly: Facebook Open-source Library
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-----------------------------------
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[](https://travis-ci.org/facebook/folly)
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### What is `folly`?
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Folly (acronymed loosely after Facebook Open Source Library) is a
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library of C++14 components designed with practicality and efficiency
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in mind. **Folly contains a variety of core library components used extensively
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at Facebook**. In particular, it's often a dependency of Facebook's other
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open source C++ efforts and place where those projects can share code.
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It complements (as opposed to competing against) offerings
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such as Boost and of course `std`. In fact, we embark on defining our
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own component only when something we need is either not available, or
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does not meet the needed performance profile. We endeavor to remove
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things from folly if or when `std` or Boost obsoletes them.
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Performance concerns permeate much of Folly, sometimes leading to
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designs that are more idiosyncratic than they would otherwise be (see
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e.g. `PackedSyncPtr.h`, `SmallLocks.h`). Good performance at large
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scale is a unifying theme in all of Folly.
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### Logical Design
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Folly is a collection of relatively independent components, some as
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simple as a few symbols. There is no restriction on internal
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dependencies, meaning that a given folly module may use any other
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folly components.
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All symbols are defined in the top-level namespace `folly`, except of
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course macros. Macro names are ALL_UPPERCASE and should be prefixed
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with `FOLLY_`. Namespace `folly` defines other internal namespaces
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such as `internal` or `detail`. User code should not depend on symbols
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in those namespaces.
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Folly has an `experimental` directory as well. This designation connotes
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primarily that we feel the API may change heavily over time. This code,
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typically, is still in heavy use and is well tested.
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### Physical Design
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At the top level Folly uses the classic "stuttering" scheme
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`folly/folly` used by Boost and others. The first directory serves as
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an installation root of the library (with possible versioning a la
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`folly-1.0/`), and the second is to distinguish the library when
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including files, e.g. `#include <folly/FBString.h>`.
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The directory structure is flat (mimicking the namespace structure),
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i.e. we don't have an elaborate directory hierarchy (it is possible
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this will change in future versions). The subdirectory `experimental`
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contains files that are used inside folly and possibly at Facebook but
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not considered stable enough for client use. Your code should not use
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files in `folly/experimental` lest it may break when you update Folly.
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The `folly/folly/test` subdirectory includes the unittests for all
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components, usually named `ComponentXyzTest.cpp` for each
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`ComponentXyz.*`. The `folly/folly/docs` directory contains
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documentation.
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### What's in it?
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Because of folly's fairly flat structure, the best way to see what's in it
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is to look at the headers in [top level `folly/` directory](https://github.com/facebook/folly/tree/master/folly). You can also
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check the [`docs` folder](folly/docs) for documentation, starting with the
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[overview](folly/docs/Overview.md).
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Folly is published on Github at https://github.com/facebook/folly
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### Build Notes
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#### Dependencies
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folly requires gcc 4.9+ and a version of boost compiled with C++14 support.
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googletest is required to build and run folly's tests. You can download
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it from https://github.com/google/googletest/archive/release-1.8.0.tar.gz
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The following commands can be used to download and install it:
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```
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wget https://github.com/google/googletest/archive/release-1.8.0.tar.gz && \
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tar zxf release-1.8.0.tar.gz && \
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rm -f release-1.8.0.tar.gz && \
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cd googletest-release-1.8.0 && \
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cmake . && \
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make && \
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make install
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```
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#### Finding dependencies in non-default locations
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If you have boost, gtest, or other dependencies installed in a non-default
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location, you can use the `CMAKE_INCLUDE_PATH` and `CMAKE_LIBRARY_PATH`
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variables to make CMAKE look also look for header files and libraries in
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non-standard locations. For example, to also search the directories
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`/alt/include/path1` and `/alt/include/path2` for header files and the
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directories `/alt/lib/path1` and `/alt/lib/path2` for libraries, you can invoke
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`cmake` as follows:
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```
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cmake \
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-DCMAKE_INCLUDE_PATH=/alt/include/path1:/alt/include/path2 \
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-DCMAKE_LIBRARY_PATH=/alt/lib/path1:/alt/lib/path2 ...
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```
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#### Ubuntu 16.04 LTS
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The following packages are required (feel free to cut and paste the apt-get
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command below):
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```
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sudo apt-get install \
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g++ \
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cmake \
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libboost-all-dev \
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libevent-dev \
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libdouble-conversion-dev \
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libgoogle-glog-dev \
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libgflags-dev \
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libiberty-dev \
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liblz4-dev \
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liblzma-dev \
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libsnappy-dev \
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make \
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zlib1g-dev \
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binutils-dev \
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libjemalloc-dev \
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libssl-dev \
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pkg-config
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```
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If advanced debugging functionality is required, use:
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```
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sudo apt-get install \
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libunwind8-dev \
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libelf-dev \
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libdwarf-dev
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```
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In the folly directory, run:
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```
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mkdir _build && cd _build
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cmake ..
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make -j $(nproc)
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make install
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```
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#### OS X (Homebrew)
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folly is available as a Formula and releases may be built via `brew install folly`.
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You may also use `folly/build/bootstrap-osx-homebrew.sh` to build against `master`:
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```
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cd folly
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./build/bootstrap-osx-homebrew.sh
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```
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#### OS X (MacPorts)
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Install the required packages from MacPorts:
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```
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sudo port install \
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autoconf \
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automake \
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boost \
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gflags \
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git \
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google-glog \
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libevent \
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libtool \
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lz4 \
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lzma \
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scons \
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snappy \
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zlib
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```
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Download and install double-conversion:
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```
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git clone https://github.com/google/double-conversion.git
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cd double-conversion
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cmake -DBUILD_SHARED_LIBS=ON .
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make
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sudo make install
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```
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Download and install folly with the parameters listed below:
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```
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git clone https://github.com/facebook/folly.git
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cd folly/folly
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autoreconf -ivf
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./configure CPPFLAGS="-I/opt/local/include" LDFLAGS="-L/opt/local/lib"
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make
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sudo make install
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```
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#### Windows (Vcpkg)
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folly is available in [Vcpkg](https://github.com/Microsoft/vcpkg#vcpkg) and releases may be built via `vcpkg install folly:x64-windows`.
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You may also use `vcpkg install folly:x64-windows --head` to build against `master`.
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#### Other Linux distributions
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- double-conversion (https://github.com/google/double-conversion)
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Download and build double-conversion.
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You may need to tell cmake where to find it.
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[double-conversion/] `ln -s src double-conversion`
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[folly/] `mkdir build && cd build`
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[folly/build/] `cmake "-DCMAKE_INCLUDE_PATH=$DOUBLE_CONVERSION_HOME/include" "-DCMAKE_LIBRARY_PATH=$DOUBLE_CONVERSION_HOME/lib" ..`
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[folly/build/] `make`
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- additional platform specific dependencies:
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Fedora >= 21 64-bit (last tested on Fedora 28 64-bit)
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- gcc
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- gcc-c++
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- cmake
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- automake
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- boost-devel
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- libtool
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- lz4-devel
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- lzma-devel
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- snappy-devel
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- zlib-devel
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- glog-devel
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- gflags-devel
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- scons
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- double-conversion-devel
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- openssl-devel
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- libevent-devel
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Optional
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- libdwarf-dev
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- libelf-dev
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- libunwind8-dev
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