Create a separate coverage build.

First part of #191.

infra/base-images/base-builder/Dockerfile

@@ -26,6 +26,9 @@ ENV SANITIZER_FLAGS_memory "-fsanitize=memory -fsanitize-memory-track-origins"
 # Default build flags for coverage.
 ENV COVERAGE_FLAGS="-fsanitize-coverage=trace-pc-guard,trace-cmp"
 
+# Coverage flags for generating coverage reports.
+ENV COVERAGE_FLAGS_coverage="-fsanitize-coverage=bb,no-prune,trace-pc-guard"
+
 # Default sanitizer and fuzzing engine to use.
 ENV SANITIZER="address"
 ENV FUZZING_ENGINE="libfuzzer"

infra/base-images/base-builder/compile

@@ -19,7 +19,7 @@ echo "---------------------------------------------------------------"
 
 if [ -z "${SANITIZER_FLAGS-}" ]; then
   FLAGS_VAR="SANITIZER_FLAGS_${SANITIZER}"
-  export SANITIZER_FLAGS=$(echo ${!FLAGS_VAR})
+  export SANITIZER_FLAGS=${!FLAGS_VAR-}
 fi
 
 # compile script might override environment, use . to call it.
@@ -32,10 +32,16 @@ then
   cp -R /usr/msan/lib/* /usr/lib/
 fi
 
+# Coverage flag overrides.
+COVERAGE_FLAGS_VAR="COVERAGE_FLAGS_$SANITIZER"
+if [[ -n ${!COVERAGE_FLAGS_VAR-} ]]
+then
+  export COVERAGE_FLAGS="${!COVERAGE_FLAGS_VAR}"
+fi
+
 export CFLAGS="$CFLAGS $SANITIZER_FLAGS $COVERAGE_FLAGS"
 export CXXFLAGS="$CFLAGS $CXXFLAGS_EXTRA"
 
-
 echo "CC=$CC"
 echo "CXX=$CXX"
 echo "CFLAGS=$CFLAGS"

infra/gcb/build.py

@@ -24,6 +24,7 @@ CONFIGURATIONS = {
   'sanitizer-address' : [ 'SANITIZER=address' ],
   'sanitizer-memory' : [ 'SANITIZER=memory' ],
   'sanitizer-undefined' : [ 'SANITIZER=undefined' ],
+  'sanitizer-coverage' : [ 'SANITIZER=coverage' ],
   'engine-libfuzzer' : [ 'FUZZING_ENGINE=libfuzzer' ],
   'engine-afl' : [ 'FUZZING_ENGINE=afl' ],
 }
@@ -34,7 +35,7 @@ EngineInfo = collections.namedtuple(
 ENGINE_INFO = {
     'libfuzzer': EngineInfo(
         upload_bucket='clusterfuzz-builds',
-        supported_sanitizers=['address', 'memory', 'undefined']),
+        supported_sanitizers=['address', 'memory', 'undefined', 'coverage']),
     'afl': EngineInfo(
         upload_bucket='clusterfuzz-builds-afl',
         supported_sanitizers=['address']),