llvm-cov - emit coverage information — LLVM 3.5 documentation

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# llvm-cov - emit coverage information

## SYNOPSIS

llvm-cov [options] SOURCEFILE

## DESCRIPTION

The llvm-cov tool reads code coverage data files and displays the coverage information for a specified source file. It is compatible with the `gcov` tool from version 4.2 of `GCC` and may also be compatible with some later versions of `gcov`.

To use llvm-cov, you must first build an instrumented version of your application that collects coverage data as it runs. Compile with the `-fprofile-arcs` and `-ftest-coverage` options to add the instrumentation. (Alternatively, you can use the `--coverage` option, which includes both of those other options.) You should compile with debugging information (`-g`) and without optimization (`-O0`); otherwise, the coverage data cannot be accurately mapped back to the source code.

At the time you compile the instrumented code, a `.gcno` data file will be generated for each object file. These `.gcno` files contain half of the coverage data. The other half of the data comes from `.gcda` files that are generated when you run the instrumented program, with a separate `.gcda` file for each object file. Each time you run the program, the execution counts are summed into any existing `.gcda` files, so be sure to remove any old files if you do not want their contents to be included.

By default, the `.gcda` files are written into the same directory as the object files, but you can override that by setting the `GCOV_PREFIX` and `GCOV_PREFIX_STRIP` environment variables. The `GCOV_PREFIX_STRIP` variable specifies a number of directory components to be removed from the start of the absolute path to the object file directory. After stripping those directories, the prefix from the `GCOV_PREFIX` variable is added. These environment variables allow you to run the instrumented program on a machine where the original object file directories are not accessible, but you will then need to copy the `.gcda` files back to the object file directories where llvm-cov expects to find them.

Once you have generated the coverage data files, run llvm-cov for each main source file where you want to examine the coverage results. This should be run from the same directory where you previously ran the compiler. The results for the specified source file are written to a file named by appending a `.gcov` suffix. A separate output file is also created for each file included by the main source file, also with a `.gcov` suffix added.

The basic content of an llvm-cov output file is a copy of the source file with an execution count and line number prepended to every line. The execution count is shown as `-` if a line does not contain any executable code. If a line contains code but that code was never executed, the count is displayed as `#####`.

## OPTIONS

`-a````,` `--all-blocks```

  Display all basic blocks. If there are multiple blocks for a single line of source code, this option causes llvm-cov to show the count for each block instead of just one count for the entire line.

`-b````,` `--branch-probabilities```

  Display conditional branch probabilities and a summary of branch information.

`-c````,` `--branch-counts```

  Display branch counts instead of probabilities (requires -b).

`-f````,` `--function-summaries```

  Show a summary of coverage for each function instead of just one summary for an entire source file.

`--help```

  Display available options (–help-hidden for more).

`-l````,` `--long-file-names```

  For coverage output of files included from the main source file, add the main file name followed by `##` as a prefix to the output file names. This can be combined with the –preserve-paths option to use complete paths for both the main file and the included file.

`-n````,` `--no-output```

  Do not output any `.gcov` files. Summary information is still displayed.

`-o``=<DIR|FILE>``,` `--object-directory``=<DIR>``,` `--object-file``=<FILE>`

  Find objects in DIR or based on FILE’s path. If you specify a particular object file, the coverage data files are expected to have the same base name with `.gcno` and `.gcda` extensions. If you specify a directory, the files are expected in that directory with the same base name as the source file.

`-p````,` `--preserve-paths```

  Preserve path components when naming the coverage output files. In addition to the source file name, include the directories from the path to that file. The directories are separate by `#` characters, with `.` directories removed and `..` directories replaced by `^` characters. When used with the –long-file-names option, this applies to both the main file name and the included file name.

`-u````,` `--unconditional-branches```

  Include unconditional branches in the output for the –branch-probabilities option.

`-version```

  Display the version of llvm-cov.

## EXIT STATUS

llvm-cov returns 1 if it cannot read input files. Otherwise, it exits with zero.

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