---
name: "llvm2lcov"
section: "1"
platform: "linux"
package: "lcov"
version: "2.6-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/llvm2lcov"
---

# llvm2lcov(1)

llvm2lcov documentation

## NAME

llvm2lcov - llvm2lcov documentation

- **Manual section**

  1

- **Manual group**

  LCOV Tools

## NAME

- **llvm2lcov**

  Translate LLVM coverage data from **llvm-cov** profdata to LCOV format

## SYNOPSIS

```
llvm2lcov [--output filename] [--testname name] [options] json_file [json_file ...]
```

## DESCRIPTION

**llvm2lcov** traverses C/C++ coverage data in JSON format (generated by **llvm-cov export -format=text ...**) and translates it into LCOV **.info** format.

Note that LLVM supports two coverage data collection paths:  the one described in this page - based on profile data - and a *gcov path* - similar to that supported by **gcc**.  See the LLVM documentation for more details about the **gcov** support in LLVM.

## MC/DC COVERAGE

To generate MC/DC data:

- •

  Use LLVM 18 or newer (LLVM 21+ recommended for cleaner MC/DC data)

- •

  Enable MC/DC instrumentation in compile/link steps with **-fcoverage-mcdc**

- •

  Pass the **--mcdc-coverage** flag to **llvm2lcov**

Note that LLVM does not support MC/DC metrics when using the **gcov** data collection path.

## OPTIONS

In addition to common options supported by other tools in the LCOV suite (*e.g.*, **--comment**, **--version-script**, **--ignore-error**, **--substitute**, **--exclude**, *etc.*), the tool provides the following options:

- **--output *filename*, -o *filename***

  The LCOV data will be written to the specified file. If this option is not used, data is written to **llvm2lcov.info** in the current directory.

- **--testname *name*, -t *name***

  Coverage info will be associated with the testcase name provided. It is not necessary to provide a name.

- **--branch-coverage**

  Include branch coverage data in the output.

- **--mcdc-coverage**

  Include MC/DC data in the output. Requires LLVM 18 or higher with MC/DC instrumentation enabled during compilation.

See **[lcov(1)](/lcov/1.md) \<file://../man/lcov.1.html\>** and **[lcovrc(5)](/lcovrc/5.md) \<file://../man/lcovrc.5.html\>** for details of other options and configuration settings.

## EXAMPLES

Basic workflow:

```
# Compile with coverage instrumentation (including MC/DC)
$ clang++ -o myExe -fprofile-inst-generate -fcoverage-mapping \
    -fcoverage-mcdc myCode.cpp
# Run your testcases
$ ./myExe ...
# Convert profile data
$ llvm-profdata merge -o myExe.profdata --sparse *.profraw
# Export coverage data in JSON format
$ llvm-cov export -format=text -instr-profile=myExe.profdata \
    ./myExe > myExe.json
# Convert to LCOV format
$ llvm2lcov --output myExe.info --test-name myTestcase \
    --mcdc-coverage --branch-coverage myExe.json ...
# Generate HTML coverage report
$ genhtml -o html_report myExe.info ...
```

(**...** indicates other tool options that you might be using - *e.g.*, for filtering and exclusion.)

Executing the same example via **gcov** looks like:

```
# Compile with gcov instrumentation
$ clang++ -o myExe --coverage myCode.cpp
# Run your testcases
$ ./myExe ...
# Convert to LCOV format
#   Note that the '--gcov-tool' option appears *twice*: once to name
#   the tool and once to pass a tool option.  See the lcov man page
#   for more information.
$ lcov --capture -d . --branch-coverage -o myExe.info --gcov-tool llvm-cov --gcov-tool gcov ...
# Generate HTML coverage report
$ genhtml -o html_report myExe.info ...
```

## AUTHOR

Henry Cox \<\<henry.cox@mediatek.com\>\>

## SEE ALSO

**[lcov(1)](/lcov/1.md) \<file://../man/lcov.1.html\>**, **[genhtml(1)](/genhtml/1.md) \<file://../man/genhtml.1.html\>**, **[geninfo(1)](/geninfo/1.md) \<file://../man/geninfo.1.html\>**, **[lcovrc(5)](/lcovrc/5.md) \<file://../man/lcovrc.5.html\>**,

- •

  LLVM documentation: \<https://llvm.org/docs/CoverageMappingFormat.html\>

- •

  **llvm-cov** documentation: \<https://llvm.org/docs/CommandGuide/llvm-cov.html\>

## Copyright

2024-2026, LCOV Project