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BUILDING.md

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Building snmalloc

snmalloc uses a CMake build system and can be built on many platforms.

Building on Windows

The Windows build currently depends on at least Visual Studio 2019. Both Visual Studio 2019 and 2022 are regularly tested in CI. Additionally, clang-cl is also supported and tested by CI. To build with Visual Studio:

mkdir build
cd build
cmake -G "Visual Studio 15 2019 Win64" ..
cmake --build . --config Debug
cmake --build . --config Release
cmake --build . --config RelWithDebInfo

You can also omit the last three steps and build from the IDE. Visual Studio builds use a separate directory to keep the binaries for each build configuration.

Alternatively, you can follow the steps in the next section to build with Ninja using the Visual Studio compiler.

Building on UNIX-like platforms

snmalloc has platform abstraction layers for XNU (macOS, iOS, and so on), FreeBSD, NetBSD, OpenBSD, and Linux and is expected to work out of the box on these systems. Please open issues if it does not. Note that NetBSD, by default, ships with a toolchain that emits calls to libatomic but does not ship libatomic. To use snmalloc on NetBSD, you must either acquire a libatomic implementation (for example, from the GCC or LLVM project) or compile with clang.

snmalloc has very few dependencies: CMake, Ninja, Clang 6.0 or later and a C++17 standard library. Building with GCC is currently not recommended because GCC emits calls to libatomic for 128-bit atomic operations.

To build a debug configuration:

mkdir build
cd build
cmake -G Ninja .. -DCMAKE_BUILD_TYPE=Debug
ninja

To build a release configuration:

mkdir build
cd build
cmake -G Ninja .. -DCMAKE_BUILD_TYPE=Release
ninja

To build with optimizations on, but with debug information:

mkdir build
cd build
cmake -G Ninja .. -DCMAKE_BUILD_TYPE=RelWithDebInfo
ninja

On ELF platforms, the build produces a binary libsnmallocshim.so. This file can be LD_PRELOADed to use the allocator in place of the system allocator, for example, you can run the build script using the snmalloc as the allocator for your toolchain:

LD_PRELOAD=/usr/local/lib/libsnmallocshim.so ninja

Cross Compile for Android

Android is supported out-of-the-box.

To cross-compile the library for arm android, you can simply invoke CMake with the toolchain file and the andorid api settings (for more infomation, check this document).

For example, you can cross-compile for arm64-v8a with the following command:

cmake /path/to/snmalloc -DCMAKE_TOOLCHAIN_FILE=${ANDROID_NDK}/build/cmake/android.toolchain.cmake -DANDROID_ABI=arm64-v8a

CMake Feature Flags

These can be added to your cmake command line.

-DUSE_SNMALLOC_STATS=ON // Track allocation stats

Using snmalloc as header-only library

In this section we show how to compile snmalloc into your project such that it replaces the standard allocator functions such as free and malloc. The following instructions were tested with CMake and Clang running on Ubuntu 18.04.

Add these lines to your CMake file.

set(SNMALLOC_HEADER_ONLY_LIBRARY ON)
add_subdirectory(snmalloc EXCLUDE_FROM_ALL)

In addition make sure your executable is compiled to support 128 bit atomic operations. This may require you to add the following to your CMake file.

target_link_libraries([lib_name] PRIVATE snmalloc_lib)

You will also need to compile the relevant parts of snmalloc itself. Create a new file with the following contents and compile it with the rest of your application.

#include "snmalloc/src/override/malloc.cc"
#include "snmalloc/src/override/new.cc"

To enable the reallocarray symbol export, this can be added to your cmake command line.

-DSNMALLOC_NO_REALLOCARRAY=OFF

likewise for reallocarr.

-DSNMALLOC_NO_REALLOCARR=OFF