[libFuzzer] update docs on -print_coverage/-dump_coverage

llvm-svn: 302498

1 files changed, 15 insertions, 4 deletions

diff --git a/llvm/docs/LibFuzzer.rst b/llvm/docs/LibFuzzer.rst
index a11baa720ec..5acfa04ce1f 100644
--- a/llvm/docs/LibFuzzer.rst
+++ b/llvm/docs/LibFuzzer.rst
@@ -305,6 +305,10 @@ The most important command line options are:
    - 1 : close ``stdout``
    - 2 : close ``stderr``
    - 3 : close both ``stdout`` and ``stderr``.
+``-print_coverage``
+   If 1, print coverage information as text at exit.
+``-dump_coverage``
+   If 1, dump coverage information as a .sancov file at exit.
 
 For the full list of flags run the fuzzer binary with ``-help=1``.
 
@@ -543,12 +547,19 @@ You can get the coverage for your corpus like this:
 
 .. code-block:: console
 
-  ASAN_OPTIONS=coverage=1 ./fuzzer CORPUS_DIR -runs=0
+  ./fuzzer CORPUS_DIR -runs=0 -print_coverage=1
 
 This will run all tests in the CORPUS_DIR but will not perform any fuzzing.
-At the end of the process it will dump a single ``.sancov`` file with coverage 
-information.  See SanitizerCoverage_ for details on querying the file using the
-``sancov`` tool.
+At the end of the process it will print text describing what code has been covered and what hasn't.
+
+Alternatively, use
+
+.. code-block:: console
+
+  ./fuzzer CORPUS_DIR -runs=0 -dump_coverage=1
+
+which will dump a ``.sancov`` file with coverage information.
+See SanitizerCoverage_ for details on querying the file using the ``sancov`` tool.
 
 You may also use other ways to visualize coverage,
 e.g. using `Clang coverage <http://clang.llvm.org/docs/SourceBasedCodeCoverage.html>`_,