[llvm-dev] Building LLVM's fuzzers (original) (raw)

Kostya Serebryany via llvm-dev llvm-dev at lists.llvm.org
Thu Aug 24 11:55:40 PDT 2017

+mascasa@ FYI

Also, I am going to file a bug to implement some improvements in the way we build and use fuzz targets in LLVM.

And, take a look at the last night's trophies: https://bugs.chromium.org/p/oss-fuzz/issues/list?q=label:Proj-llvm

On Thu, Aug 24, 2017 at 11:47 AM, George Karpenkov <ekarpenkov at apple.com> wrote:

Indeed, I can reproduce in release build. Looking into it. As a workaround, for now you could try to use debug build of fuzzers. > On Aug 24, 2017, at 11:39 AM, Justin Bogner <mail at justinbogner.com> wrote: > > George Karpenkov <ekarpenkov at apple.com> writes: >> Should -DCMAKECXXCOMPILER be also specified? > > CMake is smart enough to infer that from CCOMPILER: > > % grep CMAKECXXCOMPILER CMakeCache.txt > CMAKECXXCOMPILER:FILEPATH=/Users/bogner/llvm-lkgc/bin/clang++ > >>> On Aug 24, 2017, at 11:29 AM, Justin Bogner <mail at justinbogner.com> wrote: >>> >>> (kcc, george: sorry for the re-send, the first was from a non-list email >>> address) >>> >>> My configuration for building the fuzzers in the LLVM tree doesn't seem to >>> work any more (possibly as of moving libFuzzer to compiler-rt, but there >>> have been a few other changes in the last week or so that may be related). >>> >>> I'm building with a fresh top-of-tree clang and setting >>> -DLLVMUSESANITIZER=Address and -DLLVMUSESANITIZECOVERAGE=On, which >>> was working before: >>> _>>> % cmake -GNinja _ _>>> -DCMAKEBUILDTYPE=Release -DLLVMENABLEASSERTIONS=On _ _>>> -DLLVMENABLEWERROR=On _ _>>> -DLLVMUSESANITIZER=Address -DLLVMUSESANITIZECOVERAGE=On _ _>>> -DCMAKECCOMPILER=$HOME/llvm-lkgc/bin/clang _ >>> $HOME/code/llvm-src >>> >>> But when I run any of the fuzzers, it looks like the sanitizer coverage >>> hasn't been set up correctly: >>> >>> % ./bin/llvm-as-fuzzer 2017-08-24 11:14:33 >>> INFO: Seed: 4089166883 >>> INFO: Loaded 1 modules (50607 guards): 50607 [0x10e14ef80, 0x10e18063c), >>> INFO: Loaded 1 PC tables (0 PCs): 0 [0x10e2870a8,0x10e2870a8), >>> ERROR: The size of coverage PC tables does not match the number of instrumented PCs. This might be a bug in the compiler, please contact the libFuzzer developers. >>> >>> From the build logs, it looks like we're now building objects with these >>> sanitizer flags: >>> >>> -fsanitize=address >>> -fsanitize-address-use-after-scope >>> -fsanitize=fuzzer-no-link >>> >>> We're then linking the fuzzer binaries with these: >>> >>> -fsanitize=address >>> -fsanitize-address-use-after-scope >>> -fsanitize=fuzzer-no-link >>> -fsanitize=fuzzer >>> >>> Any idea what's wrong or where to start looking?

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