Describe how to provide preprocessor macro information.

diff --git a/etc/DEBUG b/etc/DEBUG
index 773737c65c7428b288eb0d92e9e500b7b772dc1c..0c2739cafc803f61a1d11e56a6123a97a78b8daa 100644 (file)
--- a/etc/DEBUG
+++ b/etc/DEBUG
@@ -158,12 +158,13 @@ we want the address of the l-value expression near the bottom of
 
   XVECTOR (this_command_keys)->contents[this_command_key_count++] = key;
 
-XVECTOR is a macro, and therefore, in general, GDB does not know about it.
-Unless Emacs has been compiled with preprocessor macro info, GDB cannot
-evaluate "p XVECTOR (this_command_keys)" .
+XVECTOR is a macro, so GDB only knows about it if Emacs has been compiled with
+preprocessor macro information.  GCC provides this if you specify the options
+`-gdwarf-2' and `-g3'.  In this case, GDB can evaluate expressions like
+"p XVECTOR (this_command_keys)".
 
-However, you can use the xvector command in GDB to get the same
-result.  Here is how:
+When this information isn't available, you can use the xvector command in GDB
+to get the same result.  Here is how:
 
     (gdb) p this_command_keys
     $1 = 1078005760