Add minimal LLVM sanity coverage (sancov) reporting for unittests.

This CL enables generating *.sancov data. Blacklist for sancov tool is
provided, too. Sancov tool for report generation needs to be build from
llvm compiler-rt sources (llvm 3.9.0 or newer).

See http://clang.llvm.org/docs/SanitizerCoverage.html .

BUG=webrtc:6136
R=phoglund@webrtc.org
TBR=kjellander@webrtc.org

Review URL: https://codereview.webrtc.org/2144273002 .

Cr-Commit-Position: refs/heads/master@{#13506}

tools/sancov/README

@@ -0,0 +1,9 @@
+Blacklist for llvm's sancov
+
+See http://clang.llvm.org/docs/SanitizerCoverage.html .
+
+Example usage:
+> cd out/Debug
+> UBSAN_OPTIONS="coverage=1" ./peerconnection_unittests
+> sancov -html-report -blacklist ../../tools/sancov/blacklist.txt \
+>   peerconnection_unittests peerconnection_unittests.123.sancov

tools/sancov/blacklist.txt

@@ -0,0 +1,21 @@
+#############################################################################
+# sancov blacklist.
+# Please think twice before you add or remove these rules.
+
+#############################################################################
+# no coverage report for third party
+src:*/chromium/*
+src:*/third_party/*
+
+# OpenH264 triggers some errors that are out of our control.
+src:*/third_party/ffmpeg/libavcodec/*
+src:*/third_party/openh264/*
+
+#############################################################################
+# Ignore system libraries.
+src:*/usr/*
+
+#############################################################################
+# Ignore test source.
+src:*/test/*
+src:*_unittest.cc

webrtc/BUILD.gn

@@ -18,6 +18,8 @@ import("//third_party/protobuf/proto_library.gni")
 # target_defaults and direct_dependent_settings.
 config("common_inherited_config") {
   defines = []
+  cflags = []
+  ldflags = []
   if (build_with_mozilla) {
     defines += [ "WEBRTC_MOZILLA_BUILD" ]
   }
@@ -77,6 +79,12 @@ config("common_inherited_config") {
     defines += [ "CHROMEOS" ]
   }
 
+  if (rtc_sanitize_coverage != "") {
+    assert(is_clang, "sanitizer coverage requires clang")
+    cflags += [ "-fsanitize-coverage=${rtc_sanitize_coverage}" ]
+    ldflags += [ "-fsanitize-coverage=${rtc_sanitize_coverage}" ]
+  }
+
   # TODO(GYP): Support these in GN.
   # if (is_bsd) {
   #   defines += [ "BSD" ]

webrtc/build/common.gypi

@@ -98,6 +98,13 @@
     # Set to 1 to enable code coverage on Linux using the gcov library.
     'coverage%': 0,
 
+    # Set to "func", "block", "edge" for coverage generation.
+    # At unit test runtime set UBSAN_OPTIONS="coverage=1".
+    # It is recommend to set include_examples=0.
+    # Use llvm's sancov -html-report for human readable reports.
+    # See http://clang.llvm.org/docs/SanitizerCoverage.html .
+    'webrtc_sanitize_coverage%': "",
+
     # Remote bitrate estimator logging/plotting.
     'enable_bwe_test_logging%': 0,
 
@@ -399,6 +406,17 @@
         'ldflags': [ '--coverage' ],
         'link_settings': { 'libraries': [ '-lgcov' ] },
       }],
+     ['webrtc_sanitize_coverage!=""', {
+        'cflags': [ '-fsanitize-coverage=<(webrtc_sanitize_coverage)' ],
+        'ldflags': [ '-fsanitize-coverage=<(webrtc_sanitize_coverage)' ],
+     }],
+     ['webrtc_sanitize_coverage!="" and OS=="mac"', {
+        'xcode_settings': {
+            'OTHER_CFLAGS': [
+               '-fsanitize-coverage=func',
+            ],
+         },
+      }],
       ['os_posix==1', {
         # For access to standard POSIXish features, use WEBRTC_POSIX instead of
         # a more specific macro.

webrtc/build/webrtc.gni

@@ -64,6 +64,13 @@ declare_args() {
 
   rtc_restrict_logging = true
 
+  # Set to "func", "block", "edge" for coverage generation.
+  # At unit test runtime set UBSAN_OPTIONS="coverage=1".
+  # It is recommend to set include_examples=0.
+  # Use llvm's sancov -html-report for human readable reports.
+  # See http://clang.llvm.org/docs/SanitizerCoverage.html .
+  rtc_sanitize_coverage = ""
+
   # Enable libevent task queues on platforms that support it.
   if (is_win || is_mac || is_ios || is_nacl) {
     rtc_enable_libevent = false