Clang 3.6 documentation

Sanitizer special case list

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Sanitizer special case list


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.


$ 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.
$ 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.


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.

# Lines starting with # are ignored.
# Turn off checks for the source file (use absolute path or path relative
# to the current working directory):
# Turn off checks for a particular functions (use mangled names):
# Extended regular expressions are supported:
# Shell like usage of * is supported (* is treated as .*):
# Specific sanitizer tools may introduce categories.

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