Hi folks, Ever wanted to run tests with Debug ASSERTs enabled but the speed of the Debug build is so slow that it is a drag on your productivity? Well, now you can get a faster testing build in one of two ways: 1. Build WebKit with "make testing” (or “make t”) 2. Build WebKit with “make release+assert” (or “make ra”) testing The “testing” make target builds a Debug build with the clang optimization level forced to -O3. The forcing of -O3 is achieved using "Tools/Scripts/set-webkit-configuration --force-optimization-level=O3”. See trac.webkit.org/r254080 <http://trac.webkit.org/r254080>. With this configuration, you can run JSC tests or layout tests like normal, except it will run faster. How much faster? Using a normal debug build, the JSC tests takes about 6 hours to complete. Using the “testing” build, the JSC tests takes less than 30 minutes to complete. release+assert The “release+assert” make target builds a Release build with ASSERT_ENABLED=1 defined. With this configuration, you can run JSC tests. Currently, if you run this on the layout tests, you will see a lot of ASSERT failures, which brings us to ... #if ASSERT_ENABLED vs #ifndef NDEBUG Since trac.webkit.org/r254087 <http://trac.webkit.org/r254087>, the ASSERT_DISABLED flag has been completely replaced with ASSERT_ENABLED. For code that guards fields and code needed to support debug ASSERTs, please use #if ASSERT_ENABLED going forward. Please do NOT use #ifndef NDEBUG. The reason the layout tests are failing ASSERTs when run on the “release+assert” build is because there are assertion support code above JavaScriptCore that are still guarded with #ifndef NDEBUG. If you would like to help fix some of these, do the following: 1. Build WebKit with “make release+assert”. 2. Run "Tools/Scripts/run-webkit-tests —release”. 3. Look for tests that crashed with “ASSERTION FAILED: “ in the crash log e.g. "ASSERTION FAILED: m_tokenizer.isInDataState()”. 4. Find anything that the assertion depends on which is guarded by #ifndef NDEBUG, and replace it with #if ASSERT_ENABLED. 5. Re-build WebKit and retest. In general, there is probably no reason to ever use #ifndef NDEBUG. Apart from assertion code, logging (and possibly other) code may also be affected by this same issue. Miscellaneous details The “testing” and “release+assert” make targets are available to use starting in trac.webkit.org/r254227 <http://trac.webkit.org/r254227>. I only tested these make targets on Mac. For other ports, some work may be required to get the builds configured similarly. One caution about using the “testing” target: it configures the build environment using set-webkit-configuration. That means unless you clear the configuration using "set-webkit-configuration --force-optimization-level=none”, it will force the clang optimization level to -O3 for all builds that follow, debug or release. This is similar to how "set-webkit-configuration --asan” works. Alternatively, you can also do "set-webkit-configuration —reset” to clear all configurations set using set-webkit-configuration. If typing “--force-optimization-level” is too long and painful, “--force-opt” also works. Thanks. Mark