Kevin Lubick 63bd23a8b1 Improve MSAN docs

No-Try: true
Docs-Preview: https://skia.org/?cl=118360
Bug: skia:
Change-Id: Ic6691bc0427dd0c5e9e50efd8d5bbdad8fd0012d
Reviewed-on: https://skia-review.googlesource.com/118360
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>

2018-04-03 19:31:40 +00:00

2.9 KiB

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MSAN, ASAN, & TSAN

Testing Skia with memory, address, and thread santizers.

Compiling Skia with ASAN, UBSAN, or TSAN can be done with the latest version of Clang.

UBSAN works on Linux, Mac, Android, and Windows, though some checks are platform-specific.
ASAN works on Linux, Mac, Android.
TSAN works on Linux and Mac.
MSAN works on Linux[1].

We find that testing sanitizer builds with libc++ uncovers more issues than with the system-provided C++ standard library, which is usually libstdc++. libc++ proactively hooks into sanitizers to help their analyses. We ship a copy of libc++ with our Linux toolchain in /lib.

[1]To compile and run with MSAN, an MSAN-instrumented version of libc++ is needed. It's generally easiest to run one of the following 2 steps to build/download a recent version of Clang and the instrumented libc++, located in /msan.

Downloading Clang binaries (Googlers Only)

This requires gsutil, part of the gcloud sdk.

CLANGDIR="${HOME}/clang"
python infra/bots/assets/clang_linux/download.py -t $CLANGDIR

Building Clang binaries from scratch (Other users)

CLANGDIR="${HOME}/clang"

python tools/git-sync-deps
CC= CXX= infra/bots/assets/clang_linux/create.py -t "$CLANGDIR"

Configure and Compile Skia with MSAN

CLANGDIR="${HOME}/clang"
mkdir -p out/msan
cat > out/msan/args.gn <<- EOF
    cc = "${CLANGDIR}/bin/clang"
    cxx = "${CLANGDIR}/bin/clang++"
    extra_cflags = [ "-B${CLANGDIR}/bin" ]
    extra_ldflags = [ "-B${CLANGDIR}/bin", "-fuse-ld=lld", "-L${CLANGDIR}/msan" ]
    sanitize = "MSAN"
    skia_use_fontconfig = false
    skia_use_system_freetype2 = false
    skia_enable_gpu = false
EOF
python tools/git-sync-deps
bin/gn gen out/msan
ninja -C out/msan

When you run a binary built with MSAN, make sure you force it to use our MSAN-instrumented libc++:

env LD_LIBRARY_PATH=$CLANGDIR/msan out/dm ...

Configure and Compile Skia with ASAN

CLANGDIR="${HOME}/clang"
mkdir -p out/asan
cat > out/asan/args.gn <<- EOF
    cc = "${CLANGDIR}/bin/clang"
    cxx = "${CLANGDIR}/bin/clang++"
    sanitize = "ASAN"
EOF
python tools/git-sync-deps
bin/gn gen out/asan
ninja -C out/asan

To use the libc++ that comes with the above Clang asset:

env LD_LIBRARY_PATH=$CLANGDIR/lib out/dm ...

Configure and Compile Skia with TSAN

CLANGDIR="${HOME}/clang"
mkdir -p out/tsan
cat > out/tsan/args.gn <<- EOF
    cc = "${CLANGDIR}/bin/clang"
    cxx = "${CLANGDIR}/bin/clang++"
    sanitize = "TSAN"
    is_debug = false
EOF
python tools/git-sync-deps
bin/gn gen out/tsan
ninja -C out/tsan

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