NEWS and documentation for $_gdb_setting and $_gdb_setting_str.

gdb/ChangeLog
2019-10-31  Philippe Waroquiers  <philippe.waroquiers@skynet.be>

	* NEWS: Mention $_gdb_setting, $_gdb_setting_str, $_gdb_maint_setting
	and $_gdb_maint_setting_str.

gdb/doc/ChangeLog
2019-10-31  Philippe Waroquiers  <philippe.waroquiers@skynet.be>

	* gdb.texinfo (Convenience Funs): Document the new
	$_gdb_setting_str, $_gdb_maint_setting and $_gdb_maint_setting_str
	convenience functions.

gdb/ChangeLog

@@ -1,3 +1,8 @@
+2019-10-31  Philippe Waroquiers  <philippe.waroquiers@skynet.be>
+
+	* NEWS: Mention $_gdb_setting, $_gdb_setting_str, $_gdb_maint_setting
+	and $_gdb_maint_setting_str.
+
 2019-10-31  Philippe Waroquiers  <philippe.waroquiers@skynet.be>
 
 	* cli/cli-cmds.c (setting_cmd, value_from_setting)

gdb/NEWS

@@ -11,6 +11,12 @@
   scripts that should work error-free with many different versions,
   such as in system-wide init files.
 
+* New built-in convenience functions $_gdb_setting, $_gdb_setting_str,
+  $_gdb_maint_setting and $_gdb_maint_setting_str provide access to values
+  of the GDB settings and the GDB maintenance settings.  They are handy
+  for changing the logic of user defined commands depending on the
+  current GDB settings.
+
 * GDB now supports Thread Local Storage (TLS) variables on several
   FreeBSD architectures (amd64, i386, powerpc, riscv).  Other
   architectures require kernel changes.  TLS is not yet supported for

gdb/doc/ChangeLog

@@ -1,3 +1,9 @@
+2019-10-31  Philippe Waroquiers  <philippe.waroquiers@skynet.be>
+
+	* gdb.texinfo (Convenience Funs): Document the new
+	$_gdb_setting_str, $_gdb_maint_setting and $_gdb_maint_setting_str
+	convenience functions.
+
 2019-10-29  Christian Biesinger  <cbiesinger@google.com>
 
 	* Makefile.in: Also set SYSTEM_GDBINIT_DIR for the info manual

gdb/doc/gdb.texinfo

@@ -11987,9 +11987,98 @@ $3 = void
 $4 = 1
 @end smallexample
 
+@item $_gdb_setting_str (@var{setting})
+@findex $_gdb_setting_str@r{, convenience function}
+Return the value of the @value{GDBN} @var{setting} as a string.
+@var{setting} is any setting that can be used in a @code{set} or
+@code{show} command (@pxref{Controlling GDB}).
+
+@smallexample
+(@value{GDBP}) show print frame-arguments
+Printing of non-scalar frame arguments is "scalars".
+(@value{GDBP}) p $_gdb_setting_str("print frame-arguments")
+$1 = "scalars"
+(@value{GDBP}) p $_gdb_setting_str("height")
+$2 = "30"
+(@value{GDBP})
+@end smallexample
+
+@item $_gdb_setting (@var{setting})
+@findex $_gdb_setting@r{, convenience function}
+Return the value of the @value{GDBN} @var{setting}.
+The type of the returned value depends on the setting.
+
+The value type for boolean and auto boolean settings is @code{int}.
+The boolean values @code{off} and @code{on} are converted to
+the integer values @code{0} and @code{1}.  The value @code{auto} is
+converted to the value @code{-1}.
+
+The value type for integer settings is either @code{unsigned int}
+or @code{int}, depending on the setting.
+
+Some integer settings accept an @code{unlimited} value.
+Depending on the setting, the @code{set} command also accepts
+the value @code{0} or the value @code{@minus{}1} as a synonym for
+@code{unlimited}.
+For example, @code{set height unlimited} is equivalent to
+@code{set height 0}.
+
+Some other settings that accept the @code{unlimited} value
+use the value @code{0} to literally mean zero.
+For example, @code{set history size 0} indicates to not
+record any @value{GDBN} commands in the command history.
+For such settings, @code{@minus{}1} is the synonym
+for @code{unlimited}.
+
+See the documentation of the corresponding @code{set} command for
+the numerical value equivalent to @code{unlimited}.
+
+The @code{$_gdb_setting} function converts the unlimited value
+to a @code{0} or a @code{@minus{}1} value according to what the
+@code{set} command uses.
+
+@smallexample
+@group
+(@value{GDBP}) p $_gdb_setting_str("height")
+$1 = "30"
+(@value{GDBP}) p $_gdb_setting("height")
+$2 = 30
+(@value{GDBP}) set height unlimited
+(@value{GDBP}) p $_gdb_setting_str("height")
+$3 = "unlimited"
+(@value{GDBP}) p $_gdb_setting("height")
+$4 = 0
+@end group
+@group
+(@value{GDBP}) p $_gdb_setting_str("history size")
+$5 = "unlimited"
+(@value{GDBP}) p $_gdb_setting("history size")
+$6 = -1
+(@value{GDBP}) p $_gdb_setting_str("disassemble-next-line")
+$7 = "auto"
+(@value{GDBP}) p $_gdb_setting("disassemble-next-line")
+$8 = -1
+(@value{GDBP})
+@end group
+@end smallexample
+
+Other setting types (enum, filename, optional filename, string, string noescape)
+are returned as string values.
+
+
+@item $_gdb_maint_setting_str (@var{setting})
+@findex $_gdb_maint_setting_str@r{, convenience function}
+Like the @code{$_gdb_setting_str} function, but works with
+@code{maintenance set} variables.
+
+@item $_gdb_maint_setting (@var{setting})
+@findex $_gdb_maint_setting@r{, convenience function}
+Like the @code{$_gdb_setting} function, but works with
+@code{maintenance set} variables.
+
 @end table
 
-These functions require @value{GDBN} to be configured with
+The following functions require @value{GDBN} to be configured with
 @code{Python} support.
 
 @table @code