ASan docs: no_sanitize("address") works on globals.

[eugenis]

Summary

Mention that no_sanitize attribute can be used with globals.

[aaron.ballman]

Do you also want to update AttrDocs.td with some similar information?

[eugenis]

update AttrDocs.td

[eugenis]

In D48390#1138193, @aaron.ballman wrote:

Do you also want to update AttrDocs.td with some similar information?

Done.

docs/AddressSanitizer.rst

.. code-block:: c
     #  if __has_feature(address_sanitizer)
     // code that builds only under AddressSanitizer
     #  endif
     #endif
 
 Disabling Instrumentation with ``__attribute__((no_sanitize("address")))``
 --------------------------------------------------------------------------
 
-Some code should not be instrumented by AddressSanitizer. One may use the
-function attribute ``__attribute__((no_sanitize("address")))`` (which has
-deprecated synonyms `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
+Some code should not be instrumented by AddressSanitizer. One may use
+the attribute ``__attribute__((no_sanitize("address")))`` (which has
+deprecated synonyms `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)``.
 
+The same attribute used on a global variable prevents AddressSanitizer
+from adding redzones around it and detecting out of bounds accesses.
+
 Suppressing Errors in Recompiled Code (Blacklist)
 -------------------------------------------------
 
 AddressSanitizer supports ``src`` and ``fun`` entity types in
 :doc:`SanitizerSpecialCaseList`, that can be used to suppress error reports
 in the specified source files or functions. Additionally, AddressSanitizer
 introduces ``global`` and ``type`` entity types that can be used to
 suppress error reports for out-of-bound access to globals with certain

include/clang/Basic/AttrDocs.td

 This attribute accepts a single parameter that must be one of the following:
 ``unknown``, ``consumed``, or ``unconsumed``.
   }];
 }
 
 def NoSanitizeDocs : Documentation {
   let Category = DocCatFunction;
   let Content = [{
-Use the ``no_sanitize`` attribute on a function declaration to specify
-that a particular instrumentation or set of instrumentations should not be
-applied to that function. The attribute takes a list of string literals,
-which have the same meaning as values accepted by the ``-fno-sanitize=``
-flag. For example, ``__attribute__((no_sanitize("address", "thread")))``
-specifies that AddressSanitizer and ThreadSanitizer should not be applied
-to the function.
+Use the ``no_sanitize`` attribute on a function or a global variable
+declaration to specify that a particular instrumentation or set of
+instrumentations should not be applied. The attribute takes a list of
+string literals, which have the same meaning as values accepted by the
+``-fno-sanitize=`` flag. For example,
+``__attribute__((no_sanitize("address", "thread")))`` specifies that
+AddressSanitizer and ThreadSanitizer should not be applied to the
+function or variable.
 
 See :ref:`Controlling Code Generation <controlling-code-generation>` for a
 full list of supported sanitizer flags.
   }];
 }
 
 def NoSanitizeAddressDocs : Documentation {
   let Category = DocCatFunction;
   // This function has multiple distinct spellings, and so it requires a custom
   // heading to be specified. The most common spelling is sufficient.
   let Heading = "no_sanitize_address (no_address_safety_analysis, gnu::no_address_safety_analysis, gnu::no_sanitize_address)";
   let Content = [{
 .. _langext-address_sanitizer:
 
-Use ``__attribute__((no_sanitize_address))`` on a function declaration to
-specify that address safety instrumentation (e.g. AddressSanitizer) should
-not be applied to that function.
+Use ``__attribute__((no_sanitize_address))`` on a function or a global
+variable declaration to specify that address safety instrumentation
+(e.g. AddressSanitizer) should not be applied.
   }];
 }
 
 def NoSanitizeThreadDocs : Documentation {
   let Category = DocCatFunction;
   let Heading = "no_sanitize_thread";
   let Content = [{
 .. _langext-thread_sanitizer: