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 AddressSanitizer, ThreadSanitizer or 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 they want to ignore, and pass it to clang at compile-time using -fsanitize-blacklist flag. See Clang Compiler User’s Manual for details.

Example¶

$ 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¶

Blacklists consist of entries, optionally grouped into sections. Empty lines and lines starting with “#” are ignored.

Section names are regular expressions written in square brackets that denote which sanitizer the following entries apply to. For example, [address] specifies AddressSanitizer while [cfi-vcall|cfi-icall] specifies Control Flow Integrity virtual and indirect call checking. Entries without a section will be placed under the [*] section applying to all enabled sanitizers.

Entries contain 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, e.g. fun:*ExampleFunc=example_category. The meaning 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 users to specify source files and functions, respectively. Some sanitizer tools may introduce custom entity types and categories - refer to tool-specific docs.

# 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
# Sections can be used to limit blacklist entries to specific sanitizers
[address]
fun:*BadASanFunc*
# Section names are regular expressions
[cfi-vcall|cfi-icall]
fun:*BadCfiCall
# Entries without sections are placed into [*] and apply to all sanitizers