kinda works except not

run.sh

@@ -0,0 +1,78 @@
+#!/bin/bash
+
+# from the amazing https://github.com/dwrensha/fuzz-rustc
+
+set -e
+set -x
+
+if [ ! -d rust ]; then
+    git clone https://github.com/dwrensha/rust.git --branch fuzz
+fi
+
+
+rustup override set nightly
+
+# - enable coverage instrumentation
+export RUSTFLAGS="$RUSTFLAGS -C passes=sancov-module -C llvm-args=-sanitizer-coverage-level=4"
+export RUSTFLAGS="$RUSTFLAGS -C llvm-args=-sanitizer-coverage-trace-compares"
+export RUSTFLAGS="$RUSTFLAGS -C llvm-args=-sanitizer-coverage-inline-8bit-counters"
+export RUSTFLAGS="$RUSTFLAGS -C llvm-args=-sanitizer-coverage-pc-table"
+
+# - enable compilation of rustc_private crates
+export RUSTFLAGS="$RUSTFLAGS -Z force-unstable-if-unmarked"
+
+# - work around https://github.com/rust-fuzz/cargo-fuzz/issues/161
+export RUSTFLAGS="$RUSTFLAGS -C codegen-units=1"
+
+# - enable debug assertions
+export RUSTFLAGS="$RUSTFLAGS -C debug-assertions=on"
+
+#export RUSTFLAGS="$RUSTFLAGS -Z sanitizer=address"
+
+# Create seed directory if it does not exist. Add example files here.
+mkdir -p seeds
+
+# Create corpus directory which the fuzzer will fill with interesting inputs.
+mkdir -p corpus
+
+# Create artifact output directory.
+mkdir -p artifacts
+
+# Detect the target.
+if [ "$(uname -s)" == "Darwin" ]; then
+    export TARGET="x86_64-apple-darwin"
+elif [ "$(uname -s)" == "Linux" ]; then
+    export TARGET="x86_64-unknown-linux-gnu"
+else
+    echo "Sorry, currently only Mac OS and Linux are supported"
+    exit 1
+fi
+
+# This variable tells the new rustc (i.e. the one we're compiling) what version it
+# should consider itself to have. This is used when loading precompiled libstd and other
+# crates. If the rustc version recorded in those crates' metadata does not match this,
+# then the compiler quits early.
+export CFG_VERSION=`rustc --version | cut -f2- -d ' '`
+
+# Usually we can use the precompiled libstd from rustup.
+TOOLCHAIN_ROOT=${RUSTUP_BASE:-$HOME/.rustup}/toolchains/nightly-$TARGET
+
+# If a metadata change has landed on master and is not yet in a nightly release,
+# we may need to compile our own libstd. `./x.py build --stage 1` should suffice.
+# If fuzzing immediately fails on an empty input, this is a good thing to try.
+# (Note that you will also need to change CFG_VERSION, above.)
+#TOOLCHAIN_ROOT=$HOME/src/rust/build/x86_64-unknown-linux-gnu/stage1/
+
+# Custom environment variable indicating where to look for the precompiled libstd.
+export FUZZ_RUSTC_LIBRARY_DIR=$TOOLCHAIN_ROOT/lib/rustlib/$TARGET/lib
+
+# Set some environment variables that are needed when building the rustc source code.
+export CFG_COMPILER_HOST_TRIPLE=$TARGET
+export CFG_RELEASE_CHANNEL=nightly
+export CFG_RELEASE=unknown
+export REAL_LIBRARY_PATH_VAR=foobar
+
+# Any writable location will do for this one.
+export RUSTC_ERROR_METADATA_DST=/tmp/rustc_error_metadata
+
+export RUSTC_INSTALL_BINDIR=/tmp/rustc_install_bindir