etc/DEBUG: Add more information about ASan memory poisoning.

diff --git a/etc/DEBUG b/etc/DEBUG
index c565374118d1ced64f6226d8c96dd1624779dbc8..01c75f8da7ab2bbf9373d640e2a5d5cfcf703a0c 100644 (file)
--- a/etc/DEBUG
+++ b/etc/DEBUG
@@ -1002,6 +1002,8 @@ Address sanitization is incompatible with undefined-behavior
 sanitization, unfortunately.  Address sanitization is also
 incompatible with the --with-dumping=unexec option of 'configure'.
 
+*** Address poisoning/unpoisoning
+
 When compiled with address sanitization, Emacs will also try to mark
 dead/free lisp objects as poisoned, forbidding them from being
 accessed without being unpoisoned first.  This adds an extra layer
@@ -1010,6 +1012,18 @@ evade traditional use-after-free checks. To disable this, add
 'allow_user_poisoning=0' to ASAN_OPTIONS, or build Emacs with
 '-DGC_ASAN_POISON_OBJECTS=0' in CFLAGS.
 
+While using GDB, memory addresses can be inspected by using helper
+functions additionally provided by the ASan library:
+
+  (gdb) call __asan_describe_address(ptr)
+
+To check whether an address range is poisoned or not, use:
+
+  (gdb) call __asan_region_is_poisoned(ptr, 8)
+
+Additional functions can be found in the header
+'sanitizer/asan_interface.h' in your compiler's headers directory.
+
 ** Running Emacs under Valgrind
 
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