cargo-cov doesn't work

[stasos24]

Command:

cargo cov -- show fuzz/target/<target triple>/release/my_compiler \
    --format=html \
    -instr-profile=fuzz/coverage/my_compiler/coverage.profdata \
    > index.html

Error response:

error: no such subcommand: `cov`

        Did you mean `c`?

[madig]

I "solved" this by running llvm-cov manually, like so (also install rustfilt):

/Users/user/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/x86_64-apple-darwin/bin/llvm-cov show fuzz/target/x86_64-apple-darwin/release/my_compiler \
                                         --format=html \
                                         -Xdemangler=rustfilt \
                                         --ignore-filename-regex="\.cargo" \
                                         -instr-profile=fuzz/coverage/my_compiler/coverage.profdata \
                                         > index.html

Use the llvm-cov binary you made the coverage with.

[jyn514]

hmm, that didn't work for me.

; llvm-cov show --instr-profile=/Users/jyn/src/inventory/fuzz/coverage/my_fuzz_target/coverage.profdata  --format=html -Xdemangler=rustfilt /Users/jyn/.local/lib/cargo/target/aarch64-apple-darwin/release/my_fuzz_target
error: Failed to load coverage: '/Users/jyn/.local/lib/cargo/target/aarch64-apple-darwin/release/my_fuzz_target': No coverage data found
; file /Users/jyn/.local/lib/cargo/target/aarch64-apple-darwin/release/my_fuzz_target
/Users/jyn/.local/lib/cargo/target/aarch64-apple-darwin/release/my_fuzz_target: Mach-O 64-bit executable arm64

[jix]

I was also getting the No coverage data found error, and it seems that the binary compiled with fuzzing instrumentation is at a different path from the main fuzzing binary now, but the documentation was never updated.

For me I had to change target/x86_64-unknown-linux-gnu/release/target_name to target/x86_64-unknown-linux-gnu/coverage/x86_64-unknown-linux-gnu/release/target_name (yes that includes the target triple twice) to make llvm-cov work, which makes sense when only the latter is compiled with coverage instrumentation.

[DJDuque]

I tried:

llvm-cov show target/x86_64-unknown-linux-gnu/release/fuzz_target_1 --format=html -Xdemangler=rustfilt -instr-profile=coverage/fuzz_target_1/coverage.profdata > index.html

And I get:

error: Failed to load coverage: 'coverage/fuzz_target_1/coverage.profdata': unsupported instrumentation profile format version

[0xdeafbeef]

#!/bin/bash
set -e

# Check if the correct number of arguments is provided
if [ "$#" -ne 1 ]; then
    echo "Usage: $0 <fuzz_target>"
    exit 1
fi

# Assign the first argument to the fuzz_target variable
FUZZ_TARGET=$1

# Ensure necessary tools are installed
if ! command -v cargo &> /dev/null; then
    echo "cargo could not be found, please install Rust and Cargo."
    exit 1
fi

if ! command -v llvm-cov &> /dev/null; then
    echo "llvm-cov could not be found, please install LLVM."
    exit 1
fi

if ! command -v rustfilt &> /dev/null; then
    echo "rustfilt could not be found, please install rustfilt."
    exit 1
fi

# Run the cargo fuzz coverage command with the provided fuzz target
cargo +nightly fuzz coverage "$FUZZ_TARGET"

# Define the paths
TARGET_DIR="target/x86_64-unknown-linux-gnu/coverage/x86_64-unknown-linux-gnu/release"
PROF_DATA="fuzz/coverage/$FUZZ_TARGET/coverage.profdata"
OUTPUT_FILE="index.html"

# Check if the coverage data file exists
if [ ! -f "$PROF_DATA" ]; then
    echo "Coverage data file $PROF_DATA not found."
    exit 1
fi

# Generate the coverage report in HTML format
llvm-cov show "$TARGET_DIR/$FUZZ_TARGET" --format=html \
                                         -Xdemangler=rustfilt \
                                         --ignore-filename-regex="\.cargo" \
                                         -instr-profile="$PROF_DATA" \
                                         > "$OUTPUT_FILE"

echo "Coverage report generated as $OUTPUT_FILE"

[petrosagg]

error: Failed to load coverage: 'coverage/fuzz_target_1/coverage.profdata': unsupported instrumentation profile format version

@DJDuque I hit the same issue when using my system installed llvm-cov to generate the report. If you have installed the llvm-tools or llvm-tools-preview rustup components (as it was in my case) the binaries that are used for generation of the profile are (in my case) in ~/.rustup/toolchains/nightly-2024-09-12-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/bin/. When I used the llvm-cov binary from there the report worked just fine

[nalply]

I got it running. The insights from fuzzing code coverage are amazing! Well worth the hassle. It's really complicated and confusing.

That's what I did to get it running:

• cargo install rustfilt
• PATH=$PATH:~/.cargo/bin
• cargo install llvm-tools
• Look for the binary llvm-cov, it's in ~/.rustup/toolchains/<nightly>/lib/rustlib/<target platform>/bin
• To make your life easier do alias llvm-cov=... or add that bin directory to PATH
• cd to your project root

Then!

llvm-cov show -format=html \
  -instr-profile=fuzz/coverage/<fuzz target>/coverage.profdata \
  -Xdemangler=rustfilt \
  -ignore-filename-regex=\.cargo/registry \
  target/<target platform>/coverage/<target platform>/<profile>/<fuzz target>
  > cov.html

and open the browser and smile.

Don't use the compiled binary, go into the coverage subdirectory and find your binary there! If you don't you get an error message like "no coverage data found".