From af2d0efcac11723f9be52a3dae22dec31d157e24 Mon Sep 17 00:00:00 2001
From: David Lamparter <equinox@opensourcerouting.org>
Date: Sun, 20 Mar 2016 10:09:18 +0100
Subject: [PATCH] lib: deregister memtypes on exit/unload

This is useful for DSO modules in order to get support for unloading
them dynamically.  It also runs on exit, which doesn't matter much.

At some future point, the code could be extended to check that
allocation counts are 0 on unloading a module.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
---
 lib/memory.h | 31 +++++++++++++++++++++++++------
 1 file changed, 25 insertions(+), 6 deletions(-)

diff --git a/lib/memory.h b/lib/memory.h
index 8f7d85a983..d287f229f7 100644
--- a/lib/memory.h
+++ b/lib/memory.h
@@ -30,7 +30,7 @@
 #define SIZE_VAR ~0UL
 struct memtype
 {
-  struct memtype *next;
+  struct memtype *next, **ref;
   const char *name;
   size_t n_alloc;
   size_t size;
@@ -38,7 +38,7 @@ struct memtype
 
 struct memgroup
 {
-  struct memgroup *next;
+  struct memgroup *next, **ref;
   struct memtype *types, **insert;
   const char *name;
 };
@@ -54,6 +54,7 @@ struct memgroup
 # endif
 # if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
 #  define _CONSTRUCTOR(x) constructor(x)
+#  define _DESTRUCTOR(x)  destructor(x)
 #  define _ALLOC_SIZE(x)  alloc_size(x)
 # endif
 #endif
@@ -61,6 +62,7 @@ struct memgroup
 #ifdef __sun
 /* Solaris doesn't do constructor priorities due to linker restrictions */
 # undef _CONSTRUCTOR
+# undef _DESTRUCTOR
 #endif
 
 #ifndef _RET_NONNULL
@@ -69,6 +71,9 @@ struct memgroup
 #ifndef _CONSTRUCTOR
 # define _CONSTRUCTOR(x) constructor
 #endif
+#ifndef _DESTRUCTOR
+# define _DESTRUCTOR(x) destructor
+#endif
 #ifndef _ALLOC_SIZE
 # define _ALLOC_SIZE(x)
 #endif
@@ -104,14 +109,21 @@ struct memgroup
 	struct memgroup _mg_##mname \
 	__attribute__ ((section (".data.mgroups"))) = { \
 		.name = desc, \
-		.types = NULL, .next = NULL, .insert = NULL, \
+		.types = NULL, .next = NULL, .insert = NULL, .ref = NULL, \
 	}; \
 	static void _mginit_##mname (void) \
 	  __attribute__ ((_CONSTRUCTOR (1000))); \
 	static void _mginit_##mname (void) \
 	{	extern struct memgroup **mg_insert; \
+		_mg_##mname.ref = mg_insert; \
 		*mg_insert = &_mg_##mname; \
-		mg_insert =  &_mg_##mname.next; }
+		mg_insert =  &_mg_##mname.next; } \
+	static void _mgfini_##mname (void) \
+	  __attribute__ ((_DESTRUCTOR (1000))); \
+	static void _mgfini_##mname (void) \
+	{	if (_mg_##mname.next) \
+			_mg_##mname.next->ref = _mg_##mname.ref; \
+		*_mg_##mname.ref = _mg_##mname.next; }
 
 
 #define DECLARE_MTYPE(name) \
@@ -122,15 +134,22 @@ struct memgroup
 	attr struct memtype _mt_##mname \
 	__attribute__ ((section (".data.mtypes"))) = { \
 		.name = desc, \
-		.next = NULL, .n_alloc = 0, .size = 0, \
+		.next = NULL, .n_alloc = 0, .size = 0, .ref = NULL, \
 	}; \
 	static void _mtinit_##mname (void) \
 	  __attribute__ ((_CONSTRUCTOR (1001))); \
 	static void _mtinit_##mname (void) \
 	{	if (_mg_##group.insert == NULL) \
 			_mg_##group.insert = &_mg_##group.types; \
+		_mt_##mname.ref = _mg_##group.insert; \
 		*_mg_##group.insert = &_mt_##mname; \
-		_mg_##group.insert =  &_mt_##mname.next; }
+		_mg_##group.insert =  &_mt_##mname.next; } \
+	static void _mtfini_##mname (void) \
+	  __attribute__ ((_DESTRUCTOR (1001))); \
+	static void _mtfini_##mname (void) \
+	{	if (_mt_##mname.next) \
+			_mt_##mname.next->ref = _mt_##mname.ref; \
+		*_mt_##mname.ref = _mt_##mname.next; }
 
 #define DEFINE_MTYPE(group, name, desc) \
 	DEFINE_MTYPE_ATTR(group, name, , desc)