From 8264a8cdbccce4cbc45c83f0c0c976e875976377 Mon Sep 17 00:00:00 2001 From: Anna Zaks Date: Thu, 25 Jun 2015 23:36:44 +0000 Subject: [PATCH] [docs] Several updates to the Address Sanitizer webpage. - Added the description of the interceptor suppression. - Re-organized a bit: grouped a few things under the Issue Suppression section, grouped IOC and leaks under a section, placed symbolication info into Symbolizing the Reports section.. - In supported platforms: "MacOS" -> "OS X"; added "iOS Simulator" - Added a paragraph to the Usage section describing when DYLD_INSERT_LIBRARIES might need to be used. - "attribute((no_sanitize_address))" -> "__attribute__((no_sanitize("address")))" - Updated Leak Sanitizer page with most up to date info. .... http://reviews.llvm.org/D10559 llvm-svn: 240725 --- clang/docs/AddressSanitizer.rst | 146 +++++++++++++++++++++++++++------------- clang/docs/LeakSanitizer.rst | 3 +- 2 files changed, 103 insertions(+), 46 deletions(-) diff --git a/clang/docs/AddressSanitizer.rst b/clang/docs/AddressSanitizer.rst index 6175433..66ed344 100644 --- a/clang/docs/AddressSanitizer.rst +++ b/clang/docs/AddressSanitizer.rst @@ -60,7 +60,28 @@ or: % clang -g -fsanitize=address example_UseAfterFree.o If a bug is detected, the program will print an error message to stderr and -exit with a non-zero exit code. To make AddressSanitizer symbolize its output +exit with a non-zero exit code. AddressSanitizer exits on the first detected error. +This is by design: + +* This approach allows AddressSanitizer to produce faster and smaller generated code + (both by ~5%). +* Fixing bugs becomes unavoidable. AddressSanitizer does not produce + false alarms. Once a memory corruption occurs, the program is in an inconsistent + state, which could lead to confusing results and potentially misleading + subsequent reports. + +If your process is sandboxed and you are running on OS X 10.10 or earlier, you +will need to set ``DYLD_INSERT_LIBRARIES`` environment variable and point it to +the ASan library that is packaged with the compiler used to build the +executable. (You can find the library by searching for dynamic libraries with +``asan`` in their name.) If the environment variable is not set, the process will +try to re-exec. Also keep in mind that when moving the executable to another machine, +the ASan library will also need to be copied over. + +Symbolizing the Reports +========================= + +To make AddressSanitizer symbolize its output you need to set the ``ASAN_SYMBOLIZER_PATH`` environment variable to point to the ``llvm-symbolizer`` binary (or make sure ``llvm-symbolizer`` is in your ``$PATH``): @@ -100,14 +121,63 @@ force disabled by setting ``ASAN_OPTIONS=symbolize=0``): Note that on OS X you may need to run ``dsymutil`` on your binary to have the file\:line info in the AddressSanitizer reports. -AddressSanitizer exits on the first detected error. This is by design. -One reason: it makes the generated code smaller and faster (both by -~5%). Another reason: this makes fixing bugs unavoidable. With Valgrind, -it is often the case that users treat Valgrind warnings as false -positives (which they are not) and don't fix them. +Additional Checks +================= -``__has_feature(address_sanitizer)`` ------------------------------------- +Initialization order checking +----------------------------- + +AddressSanitizer can optionally detect dynamic initialization order problems, +when initialization of globals defined in one translation unit uses +globals defined in another translation unit. To enable this check at runtime, +you should set environment variable +``ASAN_OPTIONS=check_initialization_order=1``. + +Note that this option is not supported on OS X. + +Memory leak detection +--------------------- + +For more information on leak detector in AddressSanitizer, see +:doc:`LeakSanitizer`. The leak detection is turned on by default on Linux; +however, it is not yet supported on other platforms. + +Issue Suppression +================= + +AddressSanitizer is not expected to produce false positives. If you see one, +look again; most likely it is a true positive! + +Suppressing Reports in External Libraries +----------------------------------------- +Runtime interposition allows AddressSanitizer to find bugs in code that is +not being recompiled. If you run into an issue in external libraries, we +recommend immediately reporting it to the library maintainer so that it +gets addressed. However, you can use the following suppression mechanism +to unblock yourself and continue on with the testing. This suppression +mechanism should only be used for suppressing issues in external code; it +does not work on code recompiled with AddressSanitizer. To suppress errors +in external libraries, set the ``ASAN_OPTIONS`` environment variable to point +to a suppression file. You can either specify the full path to the file or the +path of the file relative to the location of your executable. + +.. code-block:: bash + + ASAN_OPTIONS=suppressions=MyASan.supp + +Use the following format to specify the names of the functions or libraries +you want to suppress. You can see these in the error report. Remember that +the narrower the scope of the suppression, the more bugs you will be able to +catch. + +.. code-block:: bash + + interceptor_via_fun:NameOfCFunctionToSuppress + interceptor_via_fun:-[ClassName objCMethodToSuppress:] + interceptor_via_lib:NameOfTheLibraryToSuppress + +Conditional Compilation with ``__has_feature(address_sanitizer)`` +----------------------------------------------------------------- In some cases one may need to execute different code depending on whether AddressSanitizer is enabled. @@ -122,28 +192,19 @@ this purpose. # endif #endif -``__attribute__((no_sanitize_address))`` ------------------------------------------------ +Disabling Instrumentation with ``__attribute__((no_sanitize("address")))`` +-------------------------------------------------------------------------- Some code should not be instrumented by AddressSanitizer. One may use the -function attribute -:ref:`no_sanitize_address ` -(or a deprecated synonym `no_address_safety_analysis`) -to disable instrumentation of a particular function. This attribute may not be -supported by other compilers, so we suggest to use it together with -``__has_feature(address_sanitizer)``. - -Initialization order checking ------------------------------ - -AddressSanitizer can optionally detect dynamic initialization order problems, -when initialization of globals defined in one translation unit uses -globals defined in another translation unit. To enable this check at runtime, -you should set environment variable -``ASAN_OPTIONS=check_initialization_order=1``. +function attribute ``__attribute__((no_sanitize("address")))`` +(which has deprecated synonyms +:ref:`no_sanitize_address ` and +`no_address_safety_analysis`) to disable instrumentation of a particular +function. This attribute may not be supported by other compilers, so we suggest +to use it together with ``__has_feature(address_sanitizer)``. -Blacklist ---------- +Suppressing Errors in Recompiled Code (Blacklist) +------------------------------------------------- AddressSanitizer supports ``src`` and ``fun`` entity types in :doc:`SanitizerSpecialCaseList`, that can be used to suppress error reports @@ -172,24 +233,6 @@ problems happening in certain source files or with certain global variables. type:*BadInitClassSubstring*=init src:bad/init/files/*=init -Memory leak detection ---------------------- - -For the experimental memory leak detector in AddressSanitizer, see -:doc:`LeakSanitizer`. - -Supported Platforms -=================== - -AddressSanitizer is supported on - -* Linux i386/x86\_64 (tested on Ubuntu 12.04); -* MacOS 10.6 - 10.9 (i386/x86\_64). -* Android ARM -* FreeBSD i386/x86\_64 (tested on FreeBSD 11-current) - -Ports to various other platforms are in progress. - Limitations =========== @@ -202,6 +245,19 @@ Limitations usually expected. * Static linking is not supported. +Supported Platforms +=================== + +AddressSanitizer is supported on: + +* Linux i386/x86\_64 (tested on Ubuntu 12.04) +* OS X 10.7 - 10.11 (i386/x86\_64) +* iOS Simulator +* Android ARM +* FreeBSD i386/x86\_64 (tested on FreeBSD 11-current) + +Ports to various other platforms are in progress. + Current Status ============== diff --git a/clang/docs/LeakSanitizer.rst b/clang/docs/LeakSanitizer.rst index b1071ef..d4b4fa0 100644 --- a/clang/docs/LeakSanitizer.rst +++ b/clang/docs/LeakSanitizer.rst @@ -17,7 +17,8 @@ only, at a minimal performance cost. Current status ============== -LeakSanitizer is experimental and supported only on x86\_64 Linux. +LeakSanitizer is turned on by default, but it is only supported on x86\_64 +Linux. The combined mode has been tested on fairly large software projects. The stand-alone mode has received much less testing. -- 2.7.4