Import Upstream version 2.72.4

docs/macros.txt

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+GLib's configure options and corresponding macros
+=================================================
+
+--buildtype={plain,release,minsize,custom}
+	none
+--buildtype={debug,debugoptimized}	[debugoptimized is the default]
+	-DG_ENABLE_DEBUG -g
+-Dglib_debug=disabled
+	Omits G_ENABLE_DEBUG when implied by --buildtype/-Ddebug
+-Dglib_debug=enabled
+	Defines G_ENABLE_DEBUG regardless of --buildtype/-Ddebug
+-Dglib_asserts=false
+	-DG_DISABLE_ASSERT
+-Dglib_checks=false
+	-DG_DISABLE_CHECKS
+
+Besides these, there are some local feature specific options, but my main
+focus here is to concentrate on macros that affect overall GLib behaviour
+and/or third party code.
+
+
+Notes on GLib's internal and global macros
+==========================================
+
+G_DISABLE_ASSERT
+	The g_assert() and g_assert_not_reached() become non-functional
+	with this define. The motivation is to speed up end-user apps by
+	avoiding expensive checks.
+	This macro can affect third-party code. Defining it when building GLib
+	will only disable the assertion macros for GLib itself, but third-party code
+	that passes -DG_DISABLE_ASSERT to the compiler upon its own build
+	will end up with the non-functional variants after including glib.h
+	as well.
+	NOTE: Code inside the assertion macros should not have side effects
+	that affect the operation of the program.
+G_DISABLE_CHECKS
+	This macro is similar to G_DISABLE_ASSERT, it affects third-party
+	code as mentioned above and the NOTE about G_DISABLE_ASSERT applies
+	too. The macros that become non-functional here are
+	g_return_if_fail(), g_return_val_if_fail(), g_return_if_reached() and
+	g_return_val_if_reached().
+	Additionally the glib_mem_profiler_table and g_mem_profile() from
+	gmem.h become non-functional if this macro is supplied.
+	This macro also switches off certain checks in the GSignal code.
+G_ENABLE_DEBUG
+	Quite a bit of additional debugging code is compiled into GLib for this
+	macro, and since it is a globally visible define, third-party code may
+	be affected by it similar to G_DISABLE_ASSERT.
+	The additional code executed/compiled for this macro currently involve:
+	- extra validity checks for GDate
+	- memory profiling traps in gmem.c (consult debugging.txt for details)
+	- BREAKPOINT abortion for fatal log levels in gmessage.c instead of
+	  plain abort() to allow debuggers trapping and overriding them
+	- added verbosity of gscanner.c to catch deprecated code paths
+	- added verbosity of gutils.c to catch deprecated code paths
+	- object ref/unref traps (consult debugging.txt) and object bookkeeping
+	  in gobject.c
+	- extra validity checks in gsignal.c