===========================
Sanitizer special case list
===========================

.. contents::
   :local:

Introduction
============

This document describes the way to disable or alter the behavior of
sanitizer tools for certain source-level entities by providing a special
file at compile-time.

Goal and usage
==============

User of sanitizer tools, such as :doc:`AddressSanitizer`, :doc:`ThreadSanitizer`
or :doc:`MemorySanitizer` may want to disable or alter some checks for
certain source-level entities to:

* speedup hot function, which is known to be correct;
* ignore a function that does some low-level magic (e.g. walks through the
  thread stack, bypassing the frame boundaries);
* ignore a known problem.

To achieve this, user may create a file listing the entities he wants to
ignore, and pass it to clang at compile-time using
``-fsanitize-blacklist`` flag. See :doc:`UsersManual` for details.

Example
=======

.. code-block:: bash

  $ cat foo.c
  #include <stdlib.h>
  void bad_foo() {
    int *a = (int*)malloc(40);
    a[10] = 1;
  }
  int main() { bad_foo(); }
  $ cat blacklist.txt
  # Ignore reports from bad_foo function.
  fun:bad_foo
  $ clang -fsanitize=address foo.c ; ./a.out
  # AddressSanitizer prints an error report.
  $ clang -fsanitize=address -fsanitize-blacklist=blacklist.txt foo.c ; ./a.out
  # No error report here.

Format
======

Each line contains an entity type, followed by a colon and a regular
expression, specifying the names of the entities, optionally followed by
an equals sign and a tool-specific category. Empty lines and lines starting
with "#" are ignored. The meanining of ``*`` in regular expression for entity
names is different - it is treated as in shell wildcarding. Two generic
entity types are ``src`` and ``fun``, which allow user to add, respectively,
source files and functions to special case list. Some sanitizer tools may
introduce custom entity types - refer to tool-specific docs.

.. code-block:: bash

    # Lines starting with # are ignored.
    # Turn off checks for the source file (use absolute path or path relative
    # to the current working directory):
    src:/path/to/source/file.c
    # Turn off checks for a particular functions (use mangled names):
    fun:MyFooBar
    fun:_Z8MyFooBarv
    # Extended regular expressions are supported:
    fun:bad_(foo|bar)
    src:bad_source[1-9].c
    # Shell like usage of * is supported (* is treated as .*):
    src:bad/sources/*
    fun:*BadFunction*
    # Specific sanitizer tools may introduce categories.
    src:/special/path/*=special_sources