From c3d91ae1e87f8a8b8d6b0e7ecd4b7fc09837d30e Mon Sep 17 00:00:00 2001
From: Oswald Buddenhagen <ossi@users.sf.net>
Date: Thu, 17 Dec 2020 15:53:40 +0100
Subject: [PATCH] introduce new inheritance model based on C11 anonymous
 structs

the struct declarations got uglier, but their usage requires a lot fewer
explicit references to the parent struct (though some are added where
using the derived struct is more practical now).

we also use something i'd term "covariant members": derivatives of
store_t also reference derivatives of store_conf_t, etc., which
drastically cuts down the number of casts.
fwiw, to achieve this with "proper" inheritance in C++, we'd use
covariant getter functions which hide the still existing casts.

C11 is almost a decade old now, and compilers supported that feature
even longer than that, so i don't expect this to be a problem.
---
 configure.ac      |  26 ++-
 src/common.h      |  16 +-
 src/driver.h      |  49 +++---
 src/drv_imap.c    | 407 +++++++++++++++++++++++++---------------------
 src/drv_maildir.c | 212 ++++++++++++------------
 src/drv_proxy.c   |  51 +++---
 6 files changed, 423 insertions(+), 338 deletions(-)

diff --git a/configure.ac b/configure.ac
index 6496d29..ccab5cb 100644
--- a/configure.ac
+++ b/configure.ac
@@ -6,7 +6,7 @@ AC_CANONICAL_TARGET
 AM_INIT_AUTOMAKE
 AM_MAINTAINER_MODE
 
-AC_PROG_CC_C99
+AC_PROG_CC
 if test "$GCC" = yes; then
     warnings="
         -Wall -Wextra
@@ -17,9 +17,31 @@ if test "$GCC" = yes; then
 
         -Wno-overlength-strings
     "
-    CFLAGS="$CFLAGS -pipe -std=c99 -pedantic $(echo $warnings)"
+    CFLAGS="$CFLAGS -pipe -std=c11 -pedantic $(echo $warnings)"
 fi
 
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([
+void fkt(void)
+{
+    int a = 42;  // c99 comment
+
+    for (int i = 0; i < a; i++) {}  // declaration inside for()
+    int b;  // declaration after code
+}
+
+// c11 anonymous structs/unions
+struct base {
+    int a;
+};
+union deriv {
+    struct base gen;
+    struct {
+        int a;
+        int b;
+    };
+};
+])], , [AC_MSG_ERROR([compiler does not support required C11 features])])
+
 CPPFLAGS="$CPPFLAGS -D_GNU_SOURCE"
 
 AC_CHECK_PROG(PERL, perl, perl)
diff --git a/src/common.h b/src/common.h
index 63ae96f..8ced726 100644
--- a/src/common.h
+++ b/src/common.h
@@ -186,22 +186,22 @@ int map_name( const char *arg, char **result, uint reserve, const char *in, cons
 	typedef union { \
 		T##_array_t array; \
 		struct { \
-			T *dummy_data; \
-			uint dummy_size; \
+			T *data; \
+			uint size; \
 			uint alloc; \
-		} extra; \
+		}; \
 	} T##_array_alloc_t; \
 	static INLINE T *T##_array_append( T##_array_alloc_t *arr ) \
 	{ \
-		if (arr->array.size == arr->extra.alloc) { \
-			arr->extra.alloc = arr->extra.alloc * 2 + 100; \
-			arr->array.data = nfrealloc( arr->array.data, arr->extra.alloc * sizeof(T) ); \
+		if (arr->size == arr->alloc) { \
+			arr->alloc = arr->alloc * 2 + 100; \
+			arr->data = nfrealloc( arr->data, arr->alloc * sizeof(T) ); \
 		} \
-		return &arr->array.data[arr->array.size++]; \
+		return &arr->data[arr->size++]; \
 	}
 
 #define ARRAY_INIT(arr) \
-	do { (arr)->array.data = NULL; (arr)->array.size = (arr)->extra.alloc = 0; } while (0)
+	do { (arr)->data = NULL; (arr)->size = (arr)->alloc = 0; } while (0)
 
 #define ARRAY_SQUEEZE(arr) \
 	do { \
diff --git a/src/driver.h b/src/driver.h
index 21760f5..250534c 100644
--- a/src/driver.h
+++ b/src/driver.h
@@ -31,16 +31,19 @@ typedef struct driver driver_t;
 #define FAIL_WAIT   1  /* Retry after some time (if at all) */
 #define FAIL_FINAL  2  /* Don't retry until store reconfiguration */
 
-typedef struct store_conf {
-	struct store_conf *next;
-	char *name;
-	driver_t *driver;
-	const char *path; /* should this be here? its interpretation is driver-specific */
-	const char *flat_delim;
-	const char *map_inbox;
-	const char *trash;
-	uint max_size; /* off_t is overkill */
+#define STORE_CONF \
+	struct store_conf *next; \
+	char *name; \
+	driver_t *driver; \
+	const char *path;  /* should this be here? its interpretation is driver-specific */ \
+	const char *flat_delim; \
+	const char *map_inbox; \
+	const char *trash; \
+	uint max_size;  /* off_t is overkill */ \
 	char trash_remote_new, trash_only_new;
+
+typedef struct store_conf {
+	STORE_CONF
 } store_conf_t;
 
 /* For message->flags */
@@ -67,15 +70,18 @@ typedef struct store_conf {
 
 #define TUIDL 12
 
-typedef struct message {
-	struct message *next;
-	struct sync_rec *srec;
-	char *msgid; /* owned */
-	/* string_list_t *keywords; */
-	uint size; /* zero implies "not fetched" */
-	uint uid;
-	uchar flags, status;
+#define MESSAGE(message) \
+	message *next; \
+	struct sync_rec *srec; \
+	char *msgid;  /* owned */ \
+	/* string_list_t *keywords; */ \
+	uint size;  /* zero implies "not fetched" */ \
+	uint uid; \
+	uchar flags, status; \
 	char tuid[TUIDL];
+
+typedef struct message {
+	MESSAGE(struct message)
 } message_t;
 
 // For driver_t->prepare_load_box(), which may amend the passed flags.
@@ -94,10 +100,13 @@ typedef struct message {
 
 #define UIDVAL_BAD ((uint)-1)
 
+#define STORE(store) \
+	store *next; \
+	driver_t *driver; \
+	store##_conf *conf;  /* foreign */
+
 typedef struct store {
-	struct store *next;
-	driver_t *driver;
-	store_conf_t *conf; /* foreign */
+	STORE(struct store)
 } store_t;
 
 typedef struct {
diff --git a/src/drv_imap.c b/src/drv_imap.c
index 8afb0c1..310ceb6 100644
--- a/src/drv_imap.c
+++ b/src/drv_imap.c
@@ -69,17 +69,23 @@ typedef struct imap_server_conf {
 	char failed;
 } imap_server_conf_t;
 
-typedef struct {
+typedef union imap_store_conf {
 	store_conf_t gen;
-	imap_server_conf_t *server;
-	char delimiter;
-	char use_namespace;
-	char use_lsub;
+	struct {
+		STORE_CONF
+		imap_server_conf_t *server;
+		char delimiter;
+		char use_namespace;
+		char use_lsub;
+	};
 } imap_store_conf_t;
 
-typedef struct {
+typedef union imap_message {
 	message_t gen;
-/*	uint seq; will be needed when expunges are tracked */
+	struct {
+		MESSAGE(union imap_message)
+		// uint seq; will be needed when expunges are tracked
+	};
 } imap_message_t;
 
 #define NIL	(void*)0x1
@@ -93,7 +99,7 @@ typedef struct _list {
 
 #define MAX_LIST_DEPTH 5
 
-typedef struct imap_store imap_store_t;
+typedef union imap_store imap_store_t;
 
 typedef struct {
 	list_t *head, **stack[MAX_LIST_DEPTH];
@@ -103,116 +109,142 @@ typedef struct {
 
 typedef struct imap_cmd imap_cmd_t;
 
-struct imap_store {
+union imap_store {
 	store_t gen;
-	const char *label; /* foreign */
-	const char *prefix;
-	const char *name;
-	uint ref_count;
-	uint opts;
-	enum { SST_BAD, SST_HALF, SST_GOOD } state;
-	/* trash folder's existence is not confirmed yet */
-	enum { TrashUnknown, TrashChecking, TrashKnown } trashnc;
-	// What kind of BODY-less FETCH response we're expecting.
-	enum { FetchNone, FetchMsgs, FetchUidNext } fetch_sts;
-	uint got_namespace:1;
-	uint has_forwarded:1;
-	char delimiter[2]; /* hierarchy delimiter */
-	char *ns_prefix, ns_delimiter; /* NAMESPACE info */
-	string_list_t *boxes; // _list results
-	char listed; // was _list already run with these flags?
-	// note that the message counts do _not_ reflect stats from msgs,
-	// but mailbox totals.
-	int total_msgs, recent_msgs;
-	uint uidvalidity, uidnext;
-	message_t *msgs;
-	message_t **msgapp; /* FETCH results */
-	uint caps; /* CAPABILITY results */
-	string_list_t *auth_mechs;
-	parse_list_state_t parse_list_sts;
-	/* command queue */
-	imap_cmd_t *pending, **pending_append;
-	imap_cmd_t *in_progress, **in_progress_append;
-	imap_cmd_t *wait_check, **wait_check_append;
-	int nexttag, num_in_progress, num_wait_check;
-	uint buffer_mem; /* memory currently occupied by buffers in the queue */
+	struct {
+		STORE(union imap_store)
+		const char *label;  // foreign
+		const char *prefix;
+		const char *name;
+		uint ref_count;
+		uint opts;
+		enum { SST_BAD, SST_HALF, SST_GOOD } state;
+		// The trash folder's existence is not confirmed yet
+		enum { TrashUnknown, TrashChecking, TrashKnown } trashnc;
+		// What kind of BODY-less FETCH response we're expecting
+		enum { FetchNone, FetchMsgs, FetchUidNext } fetch_sts;
+		uint got_namespace:1;
+		uint has_forwarded:1;
+		char delimiter[2];  // Hierarchy delimiter
+		char *ns_prefix, ns_delimiter;  // NAMESPACE info
+		string_list_t *boxes;  // _list results
+		char listed;  // was _list already run with these flags?
+		// note that the message counts do _not_ reflect stats from msgs,
+		// but mailbox totals.
+		int total_msgs, recent_msgs;
+		uint uidvalidity, uidnext;
+		imap_message_t **msgapp, *msgs;  // FETCH results
+		uint caps;  // CAPABILITY results
+		string_list_t *auth_mechs;
+		parse_list_state_t parse_list_sts;
+		// Command queue
+		imap_cmd_t *pending, **pending_append;
+		imap_cmd_t *in_progress, **in_progress_append;
+		imap_cmd_t *wait_check, **wait_check_append;
+		int nexttag, num_in_progress, num_wait_check;
+		uint buffer_mem;  // Memory currently occupied by buffers in the queue
 
-	/* Used during sequential operations like connect */
-	enum { GreetingPending = 0, GreetingBad, GreetingOk, GreetingPreauth } greeting;
-	int expectBYE; /* LOGOUT is in progress */
-	int expectEOF; /* received LOGOUT's OK or unsolicited BYE */
-	int canceling; /* imap_cancel() is in progress */
-	union {
-		void (*imap_open)( int sts, void *aux );
-		void (*imap_cancel)( void *aux );
-	} callbacks;
-	void *callback_aux;
+		// Used during sequential operations like connect
+		enum { GreetingPending = 0, GreetingBad, GreetingOk, GreetingPreauth } greeting;
+		int expectBYE;  // LOGOUT is in progress
+		int expectEOF;  // received LOGOUT's OK or unsolicited BYE
+		int canceling;  // imap_cancel() is in progress
+		union {
+			void (*imap_open)( int sts, void *aux );
+			void (*imap_cancel)( void *aux );
+		} callbacks;
+		void *callback_aux;
 #ifdef HAVE_LIBSASL
-	sasl_conn_t *sasl;
-	int sasl_cont;
+		sasl_conn_t *sasl;
+		int sasl_cont;
 #endif
 
-	void (*bad_callback)( void *aux );
-	void *bad_callback_aux;
+		void (*bad_callback)( void *aux );
+		void *bad_callback_aux;
 
-	conn_t conn; /* this is BIG, so put it last */
+		conn_t conn;  // This is BIG, so put it last
+	};
 };
 
+#define IMAP_CMD \
+	struct imap_cmd *next; \
+	char *cmd; \
+	int tag; \
+	\
+	struct { \
+		/* Will be called on each continuation request until it resets this pointer. \
+		 * Needs to invoke bad_callback and return -1 on error, otherwise return 0. */ \
+		int (*cont)( imap_store_t *ctx, imap_cmd_t *cmd, const char *prompt ); \
+		void (*done)( imap_store_t *ctx, imap_cmd_t *cmd, int response ); \
+		char *data; \
+		uint data_len; \
+		uint uid;  /* to identify fetch responses */ \
+		char high_prio;  /* if command is queued, put it at the front of the queue. */ \
+		char wait_check;  /* Don't report success until subsequent CHECK success. */ \
+		char to_trash;  /* we are storing to trash, not current. */ \
+		char create;  /* create the mailbox if we get an error which suggests so. */ \
+		char failok;  /* Don't complain about NO response. */ \
+	} param;
+
 struct imap_cmd {
-	struct imap_cmd *next;
-	char *cmd;
-	int tag;
-
-	struct {
-		/* Will be called on each continuation request until it resets this pointer.
-		 * Needs to invoke bad_callback and return -1 on error, otherwise return 0. */
-		int (*cont)( imap_store_t *ctx, imap_cmd_t *cmd, const char *prompt );
-		void (*done)( imap_store_t *ctx, imap_cmd_t *cmd, int response );
-		char *data;
-		uint data_len;
-		uint uid; /* to identify fetch responses */
-		char high_prio; /* if command is queued, put it at the front of the queue. */
-		char wait_check;  // Don't report success until subsequent CHECK success.
-		char to_trash; /* we are storing to trash, not current. */
-		char create; /* create the mailbox if we get an error which suggests so. */
-		char failok; /* Don't complain about NO response. */
-	} param;
+	IMAP_CMD
 };
 
-typedef struct {
-	imap_cmd_t gen;
-	void (*callback)( int sts, void *aux );
+#define IMAP_CMD_SIMPLE \
+	IMAP_CMD \
+	void (*callback)( int sts, void *aux ); \
 	void *callback_aux;
+
+typedef union {
+	imap_cmd_t gen;
+	struct {
+		IMAP_CMD_SIMPLE
+	};
 } imap_cmd_simple_t;
 
-typedef struct {
+typedef union {
 	imap_cmd_simple_t gen;
-	msg_data_t *msg_data;
+	struct {
+		IMAP_CMD_SIMPLE
+		msg_data_t *msg_data;
+	};
 } imap_cmd_fetch_msg_t;
 
-typedef struct {
+typedef union {
 	imap_cmd_t gen;
-	void (*callback)( int sts, uint uid, void *aux );
-	void *callback_aux;
-	uint out_uid;
+	struct {
+		IMAP_CMD
+		void (*callback)( int sts, uint uid, void *aux );
+		void *callback_aux;
+		uint out_uid;
+	};
 } imap_cmd_out_uid_t;
 
-typedef struct {
+typedef union {
 	imap_cmd_t gen;
-	void (*callback)( int sts, message_t *msgs, void *aux );
-	void *callback_aux;
-	message_t **out_msgs;
-	uint uid;
+	struct {
+		IMAP_CMD
+		void (*callback)( int sts, message_t *msgs, void *aux );
+		void *callback_aux;
+		imap_message_t **out_msgs;
+		uint uid;
+	};
 } imap_cmd_find_new_t;
 
-typedef struct {
-	uint ref_count;
+#define IMAP_CMD_REFCOUNTED_STATE \
+	uint ref_count; \
 	int ret_val;
-} imap_cmd_refcounted_state_t;
 
 typedef struct {
+	IMAP_CMD_REFCOUNTED_STATE
+} imap_cmd_refcounted_state_t;
+
+typedef union {
 	imap_cmd_t gen;
-	imap_cmd_refcounted_state_t *state;
+	struct {
+		IMAP_CMD
+		imap_cmd_refcounted_state_t *state;
+	};
 } imap_cmd_refcounted_t;
 
 #define CAP(cap) (ctx->caps & (1 << (cap)))
@@ -283,8 +315,8 @@ new_imap_cmd( uint size )
 
 #define INIT_IMAP_CMD_X(type, cmdp, cb, aux) \
 	cmdp = (type *)new_imap_cmd( sizeof(*cmdp) ); \
-	cmdp->gen.callback = cb; \
-	cmdp->gen.callback_aux = aux;
+	cmdp->callback = cb; \
+	cmdp->callback_aux = aux;
 
 static void
 done_imap_cmd( imap_store_t *ctx, imap_cmd_t *cmd, int response )
@@ -391,7 +423,7 @@ cmd_sendable( imap_store_t *ctx, imap_cmd_t *cmd )
 		/* Don't build a queue of MOVE/COPY/APPEND commands that may all fail. */
 		return 0;
 	}
-	if (ctx->num_in_progress >= ((imap_store_conf_t *)ctx->gen.conf)->server->max_in_progress) {
+	if (ctx->num_in_progress >= ctx->conf->server->max_in_progress) {
 		/* Too many commands in flight. */
 		return 0;
 	}
@@ -628,15 +660,15 @@ imap_refcounted_new_cmd( imap_cmd_refcounted_state_t *sts )
 }
 
 #define DONE_REFCOUNTED_STATE(sts) \
-	if (!--sts->gen.ref_count) { \
-		sts->callback( sts->gen.ret_val, sts->callback_aux ); \
+	if (!--sts->ref_count) { \
+		sts->callback( sts->ret_val, sts->callback_aux ); \
 		free( sts ); \
 	}
 
 #define DONE_REFCOUNTED_STATE_ARGS(sts, finalize, ...) \
-	if (!--sts->gen.ref_count) { \
+	if (!--sts->ref_count) { \
 		finalize \
-		sts->callback( sts->gen.ret_val, __VA_ARGS__, sts->callback_aux ); \
+		sts->callback( sts->ret_val, __VA_ARGS__, sts->callback_aux ); \
 		free( sts ); \
 	}
 
@@ -1164,16 +1196,16 @@ parse_fetch_rsp( imap_store_t *ctx, list_t *list, char *s ATTR_UNUSED )
 		ctx->uidnext = uid + 1;
 	} else if (ctx->fetch_sts == FetchMsgs) {
 		cur = nfcalloc( sizeof(*cur) );
-		*ctx->msgapp = &cur->gen;
-		ctx->msgapp = &cur->gen.next;
-		cur->gen.uid = uid;
-		cur->gen.flags = mask;
-		cur->gen.status = status;
-		cur->gen.size = size;
+		*ctx->msgapp = cur;
+		ctx->msgapp = &cur->next;
+		cur->uid = uid;
+		cur->flags = mask;
+		cur->status = status;
+		cur->size = size;
 		if (msgid)
-			cur->gen.msgid = nfstrndup( msgid, msgid_len );
+			cur->msgid = nfstrndup( msgid, msgid_len );
 		if (tuid)
-			memcpy( cur->gen.tuid, tuid, TUIDL );
+			memcpy( cur->tuid, tuid, TUIDL );
 		status &= ~(M_FLAGS | M_RECENT | M_SIZE | M_HEADER);
 	} else {
 	  badrsp:
@@ -1207,7 +1239,7 @@ parse_capability( imap_store_t *ctx, char *cmd )
 					ctx->caps |= 1 << i;
 		}
 	}
-	ctx->caps &= ~((imap_store_conf_t *)ctx->gen.conf)->server->cap_mask;
+	ctx->caps &= ~ctx->conf->server->cap_mask;
 	if (!CAP(NOLOGIN))
 		add_string_list( &ctx->auth_mechs, "LOGIN" );
 }
@@ -1418,12 +1450,15 @@ prepare_box( char **buf, const imap_store_t *ctx )
 static int
 prepare_trash( char **buf, const imap_store_t *ctx )
 {
-	return prepare_name( buf, ctx, ctx->prefix, ctx->gen.conf->trash );
+	return prepare_name( buf, ctx, ctx->prefix, ctx->conf->trash );
 }
 
-typedef struct {
+typedef union {
 	imap_cmd_t gen;
-	imap_cmd_t *orig_cmd;
+	struct {
+		IMAP_CMD
+		imap_cmd_t *orig_cmd;
+	};
 } imap_cmd_trycreate_t;
 
 static void imap_open_store_greeted( imap_store_t * );
@@ -1589,7 +1624,7 @@ imap_socket_read( void *aux )
 						imap_cmd_trycreate_t *cmd2 =
 							(imap_cmd_trycreate_t *)new_imap_cmd( sizeof(*cmd2) );
 						cmd2->orig_cmd = cmdp;
-						cmd2->gen.param.high_prio = 1;
+						cmd2->param.high_prio = 1;
 						p = strchr( cmdp->cmd, '"' );
 						imap_exec( ctx, &cmd2->gen, get_cmd_result_p2,
 						           "CREATE %.*s", imap_strchr( p + 1, '"' ) - p + 1, p );
@@ -1669,7 +1704,7 @@ imap_cancel_store( store_t *gctx )
 	cancel_pending_imap_cmds( ctx );
 	free( ctx->ns_prefix );
 	free_string_list( ctx->auth_mechs );
-	free_generic_messages( ctx->msgs );
+	free_generic_messages( &ctx->msgs->gen );
 	free_string_list( ctx->boxes );
 	imap_deref( ctx );
 }
@@ -1701,12 +1736,12 @@ imap_invoke_bad_callback( imap_store_t *ctx )
 
 /******************* imap_free_store *******************/
 
-static store_t *unowned;
+static imap_store_t *unowned;
 
 static void
 imap_cancel_unowned( void *gctx )
 {
-	store_t *store, **storep;
+	imap_store_t *store, **storep;
 
 	for (storep = &unowned; (store = *storep); storep = &store->next)
 		if (store == gctx) {
@@ -1723,11 +1758,11 @@ imap_free_store( store_t *gctx )
 
 	assert( !ctx->pending && !ctx->in_progress && !ctx->wait_check );
 
-	free_generic_messages( ctx->msgs );
+	free_generic_messages( &ctx->msgs->gen );
 	ctx->msgs = NULL;
 	imap_set_bad_callback( gctx, imap_cancel_unowned, gctx );
-	gctx->next = unowned;
-	unowned = gctx;
+	ctx->next = unowned;
+	unowned = ctx;
 }
 
 /******************* imap_cleanup *******************/
@@ -1737,16 +1772,16 @@ static void imap_cleanup_p2( imap_store_t *, imap_cmd_t *, int );
 static void
 imap_cleanup( void )
 {
-	store_t *ctx, *nctx;
+	imap_store_t *ctx, *nctx;
 
 	for (ctx = unowned; ctx; ctx = nctx) {
 		nctx = ctx->next;
-		imap_set_bad_callback( ctx, (void (*)(void *))imap_cancel_store, ctx );
+		imap_set_bad_callback( &ctx->gen, (void (*)(void *))imap_cancel_store, ctx );
 		if (((imap_store_t *)ctx)->state != SST_BAD) {
 			((imap_store_t *)ctx)->expectBYE = 1;
 			imap_exec( (imap_store_t *)ctx, NULL, imap_cleanup_p2, "LOGOUT" );
 		} else {
-			imap_cancel_store( ctx );
+			imap_cancel_store( &ctx->gen );
 		}
 	}
 }
@@ -1794,20 +1829,19 @@ imap_alloc_store( store_conf_t *conf, const char *label )
 {
 	imap_store_conf_t *cfg = (imap_store_conf_t *)conf;
 	imap_server_conf_t *srvc = cfg->server;
-	imap_store_t *ctx;
-	store_t **ctxp;
+	imap_store_t *ctx, **ctxp;
 
 	/* First try to recycle a whole store. */
-	for (ctxp = &unowned; (ctx = (imap_store_t *)*ctxp); ctxp = &ctx->gen.next)
-		if (ctx->state == SST_GOOD && ctx->gen.conf == conf) {
-			*ctxp = ctx->gen.next;
+	for (ctxp = &unowned; (ctx = *ctxp); ctxp = &ctx->next)
+		if (ctx->state == SST_GOOD && ctx->conf == cfg) {
+			*ctxp = ctx->next;
 			goto gotstore;
 		}
 
 	/* Then try to recycle a server connection. */
-	for (ctxp = &unowned; (ctx = (imap_store_t *)*ctxp); ctxp = &ctx->gen.next)
-		if (ctx->state != SST_BAD && ((imap_store_conf_t *)ctx->gen.conf)->server == srvc) {
-			*ctxp = ctx->gen.next;
+	for (ctxp = &unowned; (ctx = *ctxp); ctxp = &ctx->next)
+		if (ctx->state != SST_BAD && ctx->conf->server == srvc) {
+			*ctxp = ctx->next;
 			free_string_list( ctx->boxes );
 			ctx->boxes = NULL;
 			ctx->listed = 0;
@@ -1819,7 +1853,7 @@ imap_alloc_store( store_conf_t *conf, const char *label )
 
 	/* Finally, schedule opening a new server connection. */
 	ctx = nfcalloc( sizeof(*ctx) );
-	ctx->gen.driver = &imap_driver;
+	ctx->driver = &imap_driver;
 	ctx->ref_count = 1;
 	socket_init( &ctx->conn, &srvc->sconf,
 	             (void (*)( void * ))imap_invoke_bad_callback,
@@ -1829,7 +1863,7 @@ imap_alloc_store( store_conf_t *conf, const char *label )
 	ctx->wait_check_append = &ctx->wait_check;
 
   gotsrv:
-	ctx->gen.conf = conf;
+	ctx->conf = cfg;
   gotstore:
 	ctx->label = label;
 	return &ctx->gen;
@@ -1857,15 +1891,11 @@ static void
 imap_open_store_connected( int ok, void *aux )
 {
 	imap_store_t *ctx = (imap_store_t *)aux;
-#ifdef HAVE_LIBSSL
-	imap_store_conf_t *cfg = (imap_store_conf_t *)ctx->gen.conf;
-	imap_server_conf_t *srvc = cfg->server;
-#endif
 
 	if (!ok)
 		imap_open_store_bail( ctx, FAIL_WAIT );
 #ifdef HAVE_LIBSSL
-	else if (srvc->ssl_type == SSL_IMAPS)
+	else if (ctx->conf->server->ssl_type == SSL_IMAPS)
 		socket_start_tls( &ctx->conn, imap_open_store_tlsstarted1 );
 #endif
 	else
@@ -1908,8 +1938,7 @@ static void
 imap_open_store_authenticate( imap_store_t *ctx )
 {
 #ifdef HAVE_LIBSSL
-	imap_store_conf_t *cfg = (imap_store_conf_t *)ctx->gen.conf;
-	imap_server_conf_t *srvc = cfg->server;
+	imap_server_conf_t *srvc = ctx->conf->server;
 #endif
 
 	if (ctx->greeting != GreetingPreauth) {
@@ -2108,7 +2137,7 @@ static int
 process_sasl_step( imap_store_t *ctx, int rc, const char *in, uint in_len,
                    sasl_interact_t *interact, const char **out, uint *out_len )
 {
-	imap_server_conf_t *srvc = ((imap_store_conf_t *)ctx->gen.conf)->server;
+	imap_server_conf_t *srvc = ctx->conf->server;
 
 	while (rc == SASL_INTERACT) {
 		if (process_sasl_interact( interact, srvc ) < 0)
@@ -2237,8 +2266,7 @@ done_sasl_auth( imap_store_t *ctx, imap_cmd_t *cmd ATTR_UNUSED, int response )
 static void
 imap_open_store_authenticate2( imap_store_t *ctx )
 {
-	imap_store_conf_t *cfg = (imap_store_conf_t *)ctx->gen.conf;
-	imap_server_conf_t *srvc = cfg->server;
+	imap_server_conf_t *srvc = ctx->conf->server;
 	string_list_t *mech, *cmech;
 	int auth_login = 0;
 	int skipped_login = 0;
@@ -2409,10 +2437,10 @@ imap_open_store_compress_p2( imap_store_t *ctx, imap_cmd_t *cmd ATTR_UNUSED, int
 static void
 imap_open_store_namespace( imap_store_t *ctx )
 {
-	imap_store_conf_t *cfg = (imap_store_conf_t *)ctx->gen.conf;
+	imap_store_conf_t *cfg = ctx->conf;
 
 	ctx->state = SST_HALF;
-	ctx->prefix = cfg->gen.path;
+	ctx->prefix = cfg->path;
 	ctx->delimiter[0] = cfg->delimiter;
 	if (((!ctx->prefix && cfg->use_namespace) || !cfg->delimiter) && CAP(NAMESPACE)) {
 		/* get NAMESPACE info */
@@ -2439,9 +2467,7 @@ imap_open_store_namespace_p2( imap_store_t *ctx, imap_cmd_t *cmd ATTR_UNUSED, in
 static void
 imap_open_store_namespace2( imap_store_t *ctx )
 {
-	imap_store_conf_t *cfg = (imap_store_conf_t *)ctx->gen.conf;
-
-	if (!ctx->prefix && cfg->use_namespace)
+	if (!ctx->prefix && ctx->conf->use_namespace)
 		ctx->prefix = ctx->ns_prefix;
 	if (!ctx->delimiter[0])
 		ctx->delimiter[0] = ctx->ns_delimiter;
@@ -2471,7 +2497,7 @@ imap_open_store_ssl_bail( imap_store_t *ctx )
 static void
 imap_open_store_bail( imap_store_t *ctx, int failed )
 {
-	((imap_store_conf_t *)ctx->gen.conf)->server->failed = (char)failed;
+	ctx->conf->server->failed = (char)failed;
 	ctx->callbacks.imap_open( DRV_STORE_BAD, ctx->callback_aux );
 }
 
@@ -2484,7 +2510,7 @@ imap_select_box( store_t *gctx, const char *name )
 
 	assert( !ctx->pending && !ctx->in_progress && !ctx->wait_check );
 
-	free_generic_messages( ctx->msgs );
+	free_generic_messages( &ctx->msgs->gen );
 	ctx->msgs = NULL;
 	ctx->msgapp = &ctx->msgs;
 
@@ -2498,10 +2524,13 @@ imap_get_box_path( store_t *gctx ATTR_UNUSED )
 	return NULL;
 }
 
-typedef struct {
+typedef union {
 	imap_cmd_t gen;
-	void (*callback)( int sts, uint uidvalidity, void *aux );
-	void *callback_aux;
+	struct {
+		IMAP_CMD
+		void (*callback)( int sts, uint uidvalidity, void *aux );
+		void *callback_aux;
+	};
 } imap_cmd_open_box_t;
 
 static void imap_open_box_p2( imap_store_t *, imap_cmd_t *, int );
@@ -2525,7 +2554,7 @@ imap_open_box( store_t *gctx,
 	ctx->uidnext = 0;
 
 	INIT_IMAP_CMD(imap_cmd_open_box_t, cmd, cb, aux)
-	cmd->gen.param.failok = 1;
+	cmd->param.failok = 1;
 	imap_exec( ctx, &cmd->gen, imap_open_box_p2,
 	           "SELECT \"%\\s\"", buf );
 	free( buf );
@@ -2702,10 +2731,13 @@ imap_set_range( imap_range_t *ranges, uint *nranges, int low_flags, int high_fla
 		ranges[r].flags |= (ranges[r].last <= maxlow) ? low_flags : high_flags;
 }
 
-typedef struct {
+typedef union {
 	imap_cmd_refcounted_state_t gen;
-	void (*callback)( int sts, message_t *msgs, int total_msgs, int recent_msgs, void *aux );
-	void *callback_aux;
+	struct {
+		IMAP_CMD_REFCOUNTED_STATE
+		void (*callback)( int sts, message_t *msgs, int total_msgs, int recent_msgs, void *aux );
+		void *callback_aux;
+	};
 } imap_load_box_state_t;
 
 static void imap_submit_load( imap_store_t *, const char *, int, imap_load_box_state_t * );
@@ -2778,13 +2810,13 @@ imap_sort_msgs_comp( const void *a_, const void *b_ )
 static void
 imap_sort_msgs( imap_store_t *ctx )
 {
-	uint count = count_generic_messages( ctx->msgs );
+	uint count = count_generic_messages( &ctx->msgs->gen );
 	if (count <= 1)
 		return;
 
-	message_t **t = nfmalloc( sizeof(*t) * count );
+	imap_message_t **t = nfmalloc( sizeof(*t) * count );
 
-	message_t *m = ctx->msgs;
+	imap_message_t *m = ctx->msgs;
 	for (uint i = 0; i < count; i++) {
 		t[i] = m;
 		m = m->next;
@@ -2833,9 +2865,9 @@ imap_submit_load_p3( imap_store_t *ctx, imap_load_box_state_t *sts )
 {
 	DONE_REFCOUNTED_STATE_ARGS(sts, {
 		ctx->fetch_sts = FetchNone;
-		if (sts->gen.ret_val == DRV_OK)
+		if (sts->ret_val == DRV_OK)
 			imap_sort_msgs( ctx );
-	}, ctx->msgs, ctx->total_msgs, ctx->recent_msgs)
+	}, &ctx->msgs->gen, ctx->total_msgs, ctx->recent_msgs)
 }
 
 /******************* imap_fetch_msg *******************/
@@ -2849,7 +2881,7 @@ imap_fetch_msg( store_t *ctx, message_t *msg, msg_data_t *data, int minimal,
 	imap_cmd_fetch_msg_t *cmd;
 
 	INIT_IMAP_CMD_X(imap_cmd_fetch_msg_t, cmd, cb, aux)
-	cmd->gen.gen.param.uid = msg->uid;
+	cmd->param.uid = msg->uid;
 	cmd->msg_data = data;
 	data->data = NULL;
 	imap_exec( (imap_store_t *)ctx, &cmd->gen.gen, imap_fetch_msg_p2,
@@ -2890,10 +2922,13 @@ imap_make_flags( int flags, char *buf )
 	return d;
 }
 
-typedef struct {
+typedef union {
 	imap_cmd_refcounted_state_t gen;
-	void (*callback)( int sts, void *aux );
-	void *callback_aux;
+	struct {
+		IMAP_CMD_REFCOUNTED_STATE
+		void (*callback)( int sts, void *aux );
+		void *callback_aux;
+	};
 } imap_set_msg_flags_state_t;
 
 static void imap_set_flags_p2( imap_store_t *, imap_cmd_t *, int );
@@ -2954,10 +2989,13 @@ imap_set_flags_p3( imap_set_msg_flags_state_t *sts )
 
 /******************* imap_close_box *******************/
 
-typedef struct {
+typedef union {
 	imap_cmd_refcounted_state_t gen;
-	void (*callback)( int sts, void *aux );
-	void *callback_aux;
+	struct {
+		IMAP_CMD_REFCOUNTED_STATE
+		void (*callback)( int sts, void *aux );
+		void *callback_aux;
+	};
 } imap_expunge_state_t;
 
 static void imap_close_box_p2( imap_store_t *, imap_cmd_t *, int );
@@ -2971,9 +3009,9 @@ imap_close_box( store_t *gctx,
 
 	assert( !ctx->num_wait_check );
 
-	if (ctx->gen.conf->trash && CAP(UIDPLUS)) {
+	if (ctx->conf->trash && CAP(UIDPLUS)) {
 		INIT_REFCOUNTED_STATE(imap_expunge_state_t, sts, cb, aux)
-		message_t *msg, *fmsg, *nmsg;
+		imap_message_t *msg, *fmsg, *nmsg;
 		int bl;
 		char buf[1000];
 
@@ -3030,8 +3068,8 @@ imap_trash_msg( store_t *gctx, message_t *msg,
 	char *buf;
 
 	INIT_IMAP_CMD(imap_cmd_simple_t, cmd, cb, aux)
-	cmd->gen.param.create = 1;
-	cmd->gen.param.to_trash = 1;
+	cmd->param.create = 1;
+	cmd->param.to_trash = 1;
 	if (prepare_trash( &buf, ctx ) < 0) {
 		cb( DRV_BOX_BAD, aux );
 		return;
@@ -3064,13 +3102,13 @@ imap_store_msg( store_t *gctx, msg_data_t *data, int to_trash,
 
 	INIT_IMAP_CMD(imap_cmd_out_uid_t, cmd, cb, aux)
 	ctx->buffer_mem += data->len;
-	cmd->gen.param.data_len = data->len;
-	cmd->gen.param.data = data->data;
+	cmd->param.data_len = data->len;
+	cmd->param.data = data->data;
 	cmd->out_uid = 0;
 
 	if (to_trash) {
-		cmd->gen.param.create = 1;
-		cmd->gen.param.to_trash = 1;
+		cmd->param.create = 1;
+		cmd->param.to_trash = 1;
 		if (prepare_trash( &buf, ctx ) < 0) {
 			cb( DRV_BOX_BAD, 0, aux );
 			return;
@@ -3185,15 +3223,18 @@ imap_find_new_msgs_p4( imap_store_t *ctx ATTR_UNUSED, imap_cmd_t *gcmd, int resp
 	imap_cmd_find_new_t *cmdp = (imap_cmd_find_new_t *)gcmd;
 
 	transform_box_response( &response );
-	cmdp->callback( response, *cmdp->out_msgs, cmdp->callback_aux );
+	cmdp->callback( response, &(*cmdp->out_msgs)->gen, cmdp->callback_aux );
 }
 
 /******************* imap_list_store *******************/
 
-typedef struct {
+typedef union {
 	imap_cmd_refcounted_state_t gen;
-	void (*callback)( int sts, string_list_t *, void *aux );
-	void *callback_aux;
+	struct {
+		IMAP_CMD_REFCOUNTED_STATE
+		void (*callback)( int sts, string_list_t *, void *aux );
+		void *callback_aux;
+	};
 } imap_list_store_state_t;
 
 static void imap_list_store_p2( imap_store_t *, imap_cmd_t *, int );
@@ -3204,7 +3245,7 @@ imap_list_store( store_t *gctx, int flags,
                  void (*cb)( int sts, string_list_t *boxes, void *aux ), void *aux )
 {
 	imap_store_t *ctx = (imap_store_t *)gctx;
-	imap_store_conf_t *cfg = (imap_store_conf_t *)ctx->gen.conf;
+	imap_store_conf_t *cfg = ctx->conf;
 	INIT_REFCOUNTED_STATE(imap_list_store_state_t, sts, cb, aux)
 
 	// ctx->prefix may be empty, "INBOX.", or something else.
@@ -3341,8 +3382,8 @@ imap_parse_store( conffile_t *cfg, store_conf_t **storep )
 		type = "IMAP account";
 	} else if (!strcasecmp( "IMAPStore", cfg->cmd )) {
 		store = nfcalloc( sizeof(*store) );
-		store->gen.driver = &imap_driver;
-		name = store->gen.name = nfstrdup( cfg->val );
+		store->driver = &imap_driver;
+		name = store->name = nfstrdup( cfg->val );
 		store->use_namespace = 1;
 		*storep = &store->gen;
 		memset( &sserver, 0, sizeof(sserver) );
@@ -3522,7 +3563,7 @@ imap_parse_store( conffile_t *cfg, store_conf_t **storep )
 			else if (!strcasecmp( "SubscribedOnly", cfg->cmd ))
 				store->use_lsub = parse_bool( cfg );
 			else if (!strcasecmp( "Path", cfg->cmd ))
-				store->gen.path = nfstrdup( cfg->val );
+				store->path = nfstrdup( cfg->val );
 			else if (!strcasecmp( "PathDelimiter", cfg->cmd )) {
 				if (strlen( cfg->val ) != 1) {
 					error( "%s:%d: Path delimiter must be exactly one character long\n", cfg->file, cfg->line );
@@ -3622,7 +3663,7 @@ imap_parse_store( conffile_t *cfg, store_conf_t **storep )
 		if (!store->server) {
 			store->server = nfmalloc( sizeof(sserver) );
 			memcpy( store->server, &sserver, sizeof(sserver) );
-			store->server->name = store->gen.name;
+			store->server->name = store->name;
 		} else if (acc_opt) {
 			error( "%s '%s' has both Account and account-specific options\n", type, name );
 			cfg->err = 1;
diff --git a/src/drv_maildir.c b/src/drv_maildir.c
index a836408..07b20f6 100644
--- a/src/drv_maildir.c
+++ b/src/drv_maildir.c
@@ -50,44 +50,53 @@
 #define SUB_MAILDIRPP  2
 #define SUB_LEGACY     3
 
-typedef struct {
+typedef union maildir_store_conf {
 	store_conf_t gen;
-	char *inbox;
+	struct {
+		STORE_CONF
+		char *inbox;
 #ifdef USE_DB
-	int alt_map;
+		int alt_map;
 #endif /* USE_DB */
-	char info_delimiter;
-	char sub_style;
-	char failed;
-	char *info_prefix, *info_stop; /* precalculated from info_delimiter */
+		char info_delimiter;
+		char sub_style;
+		char failed;
+		char *info_prefix, *info_stop;  /* precalculated from info_delimiter */
+	};
 } maildir_store_conf_t;
 
-typedef struct {
+typedef union maildir_message {
 	message_t gen;
-	char *base;
+	struct {
+		MESSAGE(union maildir_message)
+		char *base;
+	};
 } maildir_message_t;
 
-typedef struct {
+typedef union maildir_store {
 	store_t gen;
-	int uvfd, uvok, is_inbox, fresh[3];
-	uint opts, minuid, maxuid, finduid, pairuid, newuid, uidvalidity, nuid;
-	uint_array_t excs;
-	char *path; /* own */
-	char *trash;
+	struct {
+		STORE(union maildir_store)
+		int uvfd, uvok, is_inbox, fresh[3];
+		uint opts, minuid, maxuid, finduid, pairuid, newuid, uidvalidity, nuid;
+		uint_array_t excs;
+		char *path;  // own
+		char *trash;
 #ifdef USE_DB
-	DB *db;
-	char *usedb;
+		DB *db;
+		char *usedb;
 #endif /* USE_DB */
-	string_list_t *boxes; // _list results
-	char listed; // was _list already run with these flags?
-	// note that the message counts do _not_ reflect stats from msgs,
-	// but mailbox totals. also, don't trust them beyond the initial load.
-	int total_msgs, recent_msgs;
-	message_t *msgs;
-	wakeup_t lcktmr;
+		string_list_t *boxes;  // _list results
+		char listed;  // was _list already run with these flags?
+		// note that the message counts do _not_ reflect stats from msgs,
+		// but mailbox totals. also, don't trust them beyond the initial load.
+		int total_msgs, recent_msgs;
+		maildir_message_t *msgs;
+		wakeup_t lcktmr;
 
-	void (*bad_callback)( void *aux );
-	void *bad_callback_aux;
+		void (*bad_callback)( void *aux );
+		void *bad_callback_aux;
+	};
 } maildir_store_t;
 
 #ifdef USE_DB
@@ -130,8 +139,8 @@ maildir_parse_flags( const char *info_prefix, const char *base )
 static int
 maildir_ensure_path( maildir_store_conf_t *conf )
 {
-	if (!conf->gen.path) {
-		error( "Maildir error: store '%s' has no Path\n", conf->gen.name );
+	if (!conf->path) {
+		error( "Maildir error: store '%s' has no Path\n", conf->name );
 		conf->failed = FAIL_FINAL;
 		return -1;
 	}
@@ -153,20 +162,20 @@ maildir_join_path( maildir_store_conf_t *conf, int in_inbox, const char *box )
 	} else {
 		if (maildir_ensure_path( conf ) < 0)
 			return NULL;
-		prefix = conf->gen.path;
+		prefix = conf->path;
 	}
 	pl = strlen( prefix );
 	for (bl = 0, n = 0; (c = box[bl]); bl++)
 		if (c == '/') {
 			if (conf->sub_style == SUB_UNSET) {
 				error( "Maildir error: accessing subfolder '%s', but store '%s' does not specify SubFolders style\n",
-				       box, conf->gen.name );
+				       box, conf->name );
 				return NULL;
 			}
 			n++;
 		} else if (c == '.' && conf->sub_style == SUB_MAILDIRPP) {
 			error( "Maildir error: store '%s', folder '%s': SubFolders style Maildir++ does not support dots in mailbox names\n",
-			       conf->gen.name, box );
+			       conf->name, box );
 			return NULL;
 		}
 	switch (conf->sub_style) {
@@ -212,8 +221,8 @@ maildir_validate_path( maildir_store_conf_t *conf )
 {
 	struct stat st;
 
-	if (stat( conf->gen.path, &st ) || !S_ISDIR(st.st_mode)) {
-		error( "Maildir error: cannot open store '%s'\n", conf->gen.path );
+	if (stat( conf->path, &st ) || !S_ISDIR(st.st_mode)) {
+		error( "Maildir error: cannot open store '%s'\n", conf->path );
 		conf->failed = FAIL_FINAL;
 		return -1;
 	}
@@ -228,7 +237,7 @@ maildir_alloc_store( store_conf_t *gconf, const char *label ATTR_UNUSED )
 	maildir_store_t *ctx;
 
 	ctx = nfcalloc( sizeof(*ctx) );
-	ctx->gen.driver = &maildir_driver;
+	ctx->driver = &maildir_driver;
 	ctx->gen.conf = gconf;
 	ctx->uvfd = -1;
 	init_wakeup( &ctx->lcktmr, lcktmr_timeout, ctx );
@@ -240,13 +249,13 @@ maildir_connect_store( store_t *gctx,
                        void (*cb)( int sts, void *aux ), void *aux )
 {
 	maildir_store_t *ctx = (maildir_store_t *)gctx;
-	maildir_store_conf_t *conf = (maildir_store_conf_t *)ctx->gen.conf;
+	maildir_store_conf_t *conf = ctx->conf;
 
-	if (conf->gen.path && maildir_validate_path( conf ) < 0) {
+	if (conf->path && maildir_validate_path( conf ) < 0) {
 		cb( DRV_STORE_BAD, aux );
 		return;
 	}
-	if (conf->gen.trash && !(ctx->trash = maildir_join_path( conf, 0, conf->gen.trash ))) {
+	if (conf->trash && !(ctx->trash = maildir_join_path( conf, 0, conf->trash ))) {
 		cb( DRV_STORE_BAD, aux );
 		return;
 	}
@@ -254,13 +263,11 @@ maildir_connect_store( store_t *gctx,
 }
 
 static void
-free_maildir_messages( message_t *msg )
+free_maildir_messages( maildir_message_t *msg )
 {
-	message_t *tmsg;
-
-	for (; (tmsg = msg); msg = tmsg) {
+	for (maildir_message_t *tmsg; (tmsg = msg); msg = tmsg) {
 		tmsg = msg->next;
-		free( ((maildir_message_t *)msg)->base );
+		free( msg->base );
 		free( msg );
 	}
 }
@@ -392,7 +399,7 @@ maildir_list_recurse( maildir_store_t *ctx, int isBox, int flags,
                       char *path, int pathLen, char *name, int nameLen )
 {
 	DIR *dir;
-	int style = ((maildir_store_conf_t *)ctx->gen.conf)->sub_style;
+	int style = ctx->conf->sub_style;
 	int pl, nl;
 	struct dirent *de;
 	struct stat st;
@@ -405,7 +412,7 @@ maildir_list_recurse( maildir_store_t *ctx, int isBox, int flags,
 	}
 	if (isBox > 1 && style == SUB_UNSET) {
 		error( "Maildir error: found subfolder '%.*s', but store '%s' does not specify SubFolders style\n",
-		       nameLen - 1, name, ctx->gen.conf->name );
+		       nameLen - 1, name, ctx->conf->name );
 		closedir( dir );
 		return -1;
 	}
@@ -478,7 +485,7 @@ maildir_list_inbox( maildir_store_t *ctx, int flags, const char *basePath )
 	add_string_list( &ctx->boxes, "INBOX" );
 	return maildir_list_recurse(
 	        ctx, 1, flags, NULL, 0, basePath, basePath ? strlen( basePath ) - 1 : 0,
-	        path, nfsnprintf( path, _POSIX_PATH_MAX, "%s/", ((maildir_store_conf_t *)ctx->gen.conf)->inbox ),
+	        path, nfsnprintf( path, _POSIX_PATH_MAX, "%s/", ctx->conf->inbox ),
 	        name, nfsnprintf( name, _POSIX_PATH_MAX, "INBOX/" ) );
 }
 
@@ -491,11 +498,11 @@ maildir_list_path( maildir_store_t *ctx, int flags, const char *inbox )
 		return 0;
 	ctx->listed |= LIST_PATH;
 
-	if (maildir_ensure_path( (maildir_store_conf_t *)ctx->gen.conf ) < 0)
+	if (maildir_ensure_path( ctx->conf ) < 0)
 		return -1;
 	return maildir_list_recurse(
 	        ctx, 0, flags, inbox, inbox ? strlen( inbox ) : 0, NULL, 0,
-	        path, nfsnprintf( path, _POSIX_PATH_MAX, "%s", ctx->gen.conf->path ),
+	        path, nfsnprintf( path, _POSIX_PATH_MAX, "%s", ctx->conf->path ),
 	        name, 0 );
 }
 
@@ -504,14 +511,14 @@ maildir_list_store( store_t *gctx, int flags,
                     void (*cb)( int sts, string_list_t *boxes, void *aux ), void *aux )
 {
 	maildir_store_t *ctx = (maildir_store_t *)gctx;
-	maildir_store_conf_t *conf = (maildir_store_conf_t *)gctx->conf;
+	maildir_store_conf_t *conf = ctx->conf;
 
 	if (conf->sub_style == SUB_MAILDIRPP
 	        ? maildir_list_maildirpp( ctx, flags, conf->inbox ) < 0
-	        : ((((flags & LIST_PATH) || ((flags & LIST_PATH_MAYBE) && gctx->conf->path))
+	        : ((((flags & LIST_PATH) || ((flags & LIST_PATH_MAYBE) && conf->path))
 	            && maildir_list_path( ctx, flags, conf->inbox ) < 0) ||
 	           ((flags & LIST_INBOX)
-	            && maildir_list_inbox( ctx, flags, gctx->conf->path ) < 0))) {
+	            && maildir_list_inbox( ctx, flags, conf->path ) < 0))) {
 		maildir_invoke_bad_callback( ctx );
 		cb( DRV_CANCELED, NULL, aux );
 	} else {
@@ -611,7 +618,7 @@ maildir_validate( const char *box, int create, maildir_store_t *ctx )
 			return DRV_BOX_BAD;
 		if (make_box_dir( buf, bl )) {
 			sys_error( "Maildir error: cannot create mailbox '%s'", box );
-			((maildir_store_conf_t *)ctx->gen.conf)->failed = FAIL_FINAL;
+			ctx->conf->failed = FAIL_FINAL;
 			maildir_invoke_bad_callback( ctx );
 			return DRV_CANCELED;
 		}
@@ -832,7 +839,7 @@ maildir_set_uid( maildir_store_t *ctx, const char *name, uint *uid )
 		return ret;
 	*uid = ++ctx->nuid;
 
-	make_key( ((maildir_store_conf_t *)ctx->gen.conf)->info_stop, &key, name );
+	make_key( ctx->conf->info_stop, &key, name );
 	value.data = uid;
 	value.size = sizeof(*uid);
 	if ((ret = ctx->db->put( ctx->db, NULL, &key, &value, 0 ))) {
@@ -909,7 +916,7 @@ maildir_compare( const void *l, const void *r )
 static int
 maildir_scan( maildir_store_t *ctx, msg_t_array_alloc_t *msglist )
 {
-	maildir_store_conf_t *conf = (maildir_store_conf_t *)ctx->gen.conf;
+	maildir_store_conf_t *conf = ctx->conf;
 	DIR *d;
 	FILE *f;
 	struct dirent *e;
@@ -1218,37 +1225,37 @@ maildir_init_msg( maildir_store_t *ctx, maildir_message_t *msg, msg_t *entry )
 {
 	msg->base = entry->base;
 	entry->base = NULL; /* prevent deletion */
-	msg->gen.msgid = entry->msgid;
+	msg->msgid = entry->msgid;
 	entry->msgid = NULL; /* prevent deletion */
-	msg->gen.size = entry->size;
-	msg->gen.srec = NULL;
-	memcpy( msg->gen.tuid, entry->tuid, TUIDL );
+	msg->size = entry->size;
+	msg->srec = NULL;
+	memcpy( msg->tuid, entry->tuid, TUIDL );
 	if (entry->recent)
-		msg->gen.status |= M_RECENT;
+		msg->status |= M_RECENT;
 	if (ctx->opts & OPEN_FLAGS) {
-		msg->gen.status |= M_FLAGS;
-		msg->gen.flags = maildir_parse_flags( ((maildir_store_conf_t *)ctx->gen.conf)->info_prefix, msg->base );
+		msg->status |= M_FLAGS;
+		msg->flags = maildir_parse_flags( ctx->conf->info_prefix, msg->base );
 	} else
-		msg->gen.flags = 0;
+		msg->flags = 0;
 }
 
 static void
-maildir_app_msg( maildir_store_t *ctx, message_t ***msgapp, msg_t *entry )
+maildir_app_msg( maildir_store_t *ctx, maildir_message_t ***msgapp, msg_t *entry )
 {
 	maildir_message_t *msg = nfmalloc( sizeof(*msg) );
-	msg->gen.next = **msgapp;
-	**msgapp = &msg->gen;
-	*msgapp = &msg->gen.next;
-	msg->gen.uid = entry->uid;
-	msg->gen.status = 0;
+	msg->next = **msgapp;
+	**msgapp = msg;
+	*msgapp = &msg->next;
+	msg->uid = entry->uid;
+	msg->status = 0;
 	maildir_init_msg( ctx, msg, entry );
 }
 
 static int
 maildir_select_box( store_t *gctx, const char *name )
 {
-	maildir_store_conf_t *conf = (maildir_store_conf_t *)gctx->conf;
 	maildir_store_t *ctx = (maildir_store_t *)gctx;
+	maildir_store_conf_t *conf = ctx->conf;
 
 	maildir_cleanup( gctx );
 	ctx->msgs = NULL;
@@ -1304,7 +1311,7 @@ maildir_open_box( store_t *gctx,
 	if ((ctx->uvfd = open( uvpath, O_RDWR, 0600 )) < 0) {
 		nfsnprintf( uvpath, sizeof(uvpath), "%s/.isyncuidmap.db", ctx->path );
 		if ((ctx->uvfd = open( uvpath, O_RDWR, 0600 )) < 0) {
-			if (((maildir_store_conf_t *)gctx->conf)->alt_map) {
+			if (ctx->conf->alt_map) {
 				if ((ctx->uvfd = open( uvpath, O_RDWR|O_CREAT, 0600 )) >= 0)
 					goto dbok;
 			} else {
@@ -1439,7 +1446,7 @@ maildir_load_box( store_t *gctx, uint minuid, uint maxuid, uint finduid, uint pa
                   void (*cb)( int sts, message_t *msgs, int total_msgs, int recent_msgs, void *aux ), void *aux )
 {
 	maildir_store_t *ctx = (maildir_store_t *)gctx;
-	message_t **msgapp;
+	maildir_message_t **msgapp;
 	msg_t_array_alloc_t msglist;
 	uint i;
 
@@ -1460,23 +1467,20 @@ maildir_load_box( store_t *gctx, uint minuid, uint maxuid, uint finduid, uint pa
 		maildir_app_msg( ctx, &msgapp, msglist.array.data + i );
 	maildir_free_scan( &msglist );
 
-	cb( DRV_OK, ctx->msgs, ctx->total_msgs, ctx->recent_msgs, aux );
+	cb( DRV_OK, &ctx->msgs->gen, ctx->total_msgs, ctx->recent_msgs, aux );
 }
 
 static int
 maildir_rescan( maildir_store_t *ctx )
 {
-	message_t **msgapp;
-	maildir_message_t *msg;
+	maildir_message_t **msgapp, *msg;
 	msg_t_array_alloc_t msglist;
 	uint i;
 
 	ctx->fresh[0] = ctx->fresh[1] = 0;
 	if (maildir_scan( ctx, &msglist ) != DRV_OK)
 		return DRV_BOX_BAD;
-	for (msgapp = &ctx->msgs, i = 0;
-	     (msg = (maildir_message_t *)*msgapp) || i < msglist.array.size; )
-	{
+	for (msgapp = &ctx->msgs, i = 0; (msg = *msgapp) || i < msglist.array.size; ) {
 		if (!msg) {
 #if 0
 			debug( "adding new message %u\n", msglist.array.data[i].uid );
@@ -1486,10 +1490,10 @@ maildir_rescan( maildir_store_t *ctx )
 #endif
 			i++;
 		} else if (i >= msglist.array.size) {
-			debug( "purging deleted message %u\n", msg->gen.uid );
-			msg->gen.status = M_DEAD;
-			msgapp = &msg->gen.next;
-		} else if (msglist.array.data[i].uid < msg->gen.uid) {
+			debug( "purging deleted message %u\n", msg->uid );
+			msg->status = M_DEAD;
+			msgapp = &msg->next;
+		} else if (msglist.array.data[i].uid < msg->uid) {
 			/* this should not happen, actually */
 #if 0
 			debug( "adding new message %u\n", msglist.array.data[i].uid );
@@ -1498,17 +1502,17 @@ maildir_rescan( maildir_store_t *ctx )
 			debug( "ignoring new message %u\n", msglist.array.data[i].uid );
 #endif
 			i++;
-		} else if (msglist.array.data[i].uid > msg->gen.uid) {
-			debug( "purging deleted message %u\n", msg->gen.uid );
-			msg->gen.status = M_DEAD;
-			msgapp = &msg->gen.next;
+		} else if (msglist.array.data[i].uid > msg->uid) {
+			debug( "purging deleted message %u\n", msg->uid );
+			msg->status = M_DEAD;
+			msgapp = &msg->next;
 		} else {
-			debug( "updating message %u\n", msg->gen.uid );
-			msg->gen.status &= ~(M_FLAGS|M_RECENT);
+			debug( "updating message %u\n", msg->uid );
+			msg->status &= ~(M_FLAGS|M_RECENT);
 			free( msg->base );
-			free( msg->gen.msgid );
+			free( msg->msgid );
 			maildir_init_msg( ctx, msg, msglist.array.data + i );
-			i++, msgapp = &msg->gen.next;
+			i++, msgapp = &msg->next;
 		}
 	}
 	maildir_free_scan( &msglist );
@@ -1529,7 +1533,7 @@ maildir_again( maildir_store_t *ctx, maildir_message_t *msg, const char *err, ..
 	}
 	if ((ret = maildir_rescan( ctx )) != DRV_OK)
 		return ret;
-	return (msg->gen.status & M_DEAD) ? DRV_MSG_BAD : DRV_OK;
+	return (msg->status & M_DEAD) ? DRV_MSG_BAD : DRV_OK;
 }
 
 static void
@@ -1564,7 +1568,7 @@ maildir_fetch_msg( store_t *gctx, message_t *gmsg, msg_data_t *data, int minimal
 	}
 	close( fd );
 	if (!(gmsg->status & M_FLAGS))
-		data->flags = maildir_parse_flags( ((maildir_store_conf_t *)gctx->conf)->info_prefix, msg->base );
+		data->flags = maildir_parse_flags( ctx->conf->info_prefix, msg->base );
 	cb( DRV_OK, aux );
 }
 
@@ -1618,7 +1622,7 @@ maildir_store_msg( store_t *gctx, msg_data_t *data, int to_trash,
 		box = ctx->trash;
 	}
 
-	maildir_make_flags( ((maildir_store_conf_t *)gctx->conf)->info_delimiter, data->flags, fbuf );
+	maildir_make_flags( ctx->conf->info_delimiter, data->flags, fbuf );
 	nfsnprintf( buf, sizeof(buf), "%s/tmp/%s%s", box, base, fbuf );
 	if ((fd = open( buf, O_WRONLY|O_CREAT|O_EXCL, 0600 )) < 0) {
 		if (errno != ENOENT || !to_trash) {
@@ -1682,8 +1686,8 @@ static void
 maildir_set_msg_flags( store_t *gctx, message_t *gmsg, uint uid ATTR_UNUSED, int add, int del,
                        void (*cb)( int sts, void *aux ), void *aux )
 {
-	maildir_store_conf_t *conf = (maildir_store_conf_t *)gctx->conf;
 	maildir_store_t *ctx = (maildir_store_t *)gctx;
+	maildir_store_conf_t *conf = ctx->conf;
 	maildir_message_t *msg = (maildir_message_t *)gmsg;
 	char *s, *p;
 	uint i;
@@ -1729,8 +1733,8 @@ maildir_set_msg_flags( store_t *gctx, message_t *gmsg, uint uid ATTR_UNUSED, int
 	}
 	free( msg->base );
 	msg->base = nfstrndup( nbuf + bl, (size_t)tl );
-	msg->gen.flags |= add;
-	msg->gen.flags &= ~del;
+	msg->flags |= add;
+	msg->flags &= ~del;
 	gmsg->status &= ~M_RECENT;
 
 	cb( DRV_OK, aux );
@@ -1744,7 +1748,7 @@ maildir_purge_msg( maildir_store_t *ctx, const char *name )
 
 	if ((ret = maildir_uidval_lock( ctx )) != DRV_OK)
 		return ret;
-	make_key( ((maildir_store_conf_t *)ctx->gen.conf)->info_stop, &key, name );
+	make_key( ctx->conf->info_stop, &key, name );
 	if ((ret = ctx->db->del( ctx->db, NULL, &key, 0 ))) {
 		ctx->db->err( ctx->db, ret, "Maildir error: db->del()" );
 		return DRV_BOX_BAD;
@@ -1766,7 +1770,7 @@ maildir_trash_msg( store_t *gctx, message_t *gmsg,
 
 	for (;;) {
 		nfsnprintf( buf, sizeof(buf), "%s/%s/%s", ctx->path, subdirs[gmsg->status & M_RECENT], msg->base );
-		s = strstr( msg->base, ((maildir_store_conf_t *)gctx->conf)->info_prefix );
+		s = strstr( msg->base, ctx->conf->info_prefix );
 		nfsnprintf( nbuf, sizeof(nbuf), "%s/%s/%lld.%d_%d.%s%s", ctx->trash,
 		            subdirs[gmsg->status & M_RECENT], (long long)time( NULL ), Pid, ++MaildirCount, Hostname, s ? s : "" );
 		if (!rename( buf, nbuf ))
@@ -1806,7 +1810,7 @@ maildir_close_box( store_t *gctx,
                    void (*cb)( int sts, void *aux ), void *aux )
 {
 	maildir_store_t *ctx = (maildir_store_t *)gctx;
-	message_t *msg;
+	maildir_message_t *msg;
 	int basel, retry, ret;
 	char buf[_POSIX_PATH_MAX];
 
@@ -1815,7 +1819,7 @@ maildir_close_box( store_t *gctx,
 		basel = nfsnprintf( buf, sizeof(buf), "%s/", ctx->path );
 		for (msg = ctx->msgs; msg; msg = msg->next)
 			if (!(msg->status & M_DEAD) && (msg->flags & F_DELETED)) {
-				nfsnprintf( buf + basel, _POSIX_PATH_MAX - basel, "%s/%s", subdirs[msg->status & M_RECENT], ((maildir_message_t *)msg)->base );
+				nfsnprintf( buf + basel, _POSIX_PATH_MAX - basel, "%s/%s", subdirs[msg->status & M_RECENT], msg->base );
 				if (unlink( buf )) {
 					if (errno == ENOENT)
 						retry = 1;
@@ -1825,7 +1829,7 @@ maildir_close_box( store_t *gctx,
 					msg->status |= M_DEAD;
 					ctx->total_msgs--;
 #ifdef USE_DB
-					if (ctx->db && (ret = maildir_purge_msg( ctx, ((maildir_message_t *)msg)->base )) != DRV_OK) {
+					if (ctx->db && (ret = maildir_purge_msg( ctx, msg->base )) != DRV_OK) {
 						cb( ret, aux );
 						return;
 					}
@@ -1877,14 +1881,14 @@ maildir_parse_store( conffile_t *cfg, store_conf_t **storep )
 		return 0;
 	store = nfcalloc( sizeof(*store) );
 	store->info_delimiter = FieldDelimiter;
-	store->gen.driver = &maildir_driver;
-	store->gen.name = nfstrdup( cfg->val );
+	store->driver = &maildir_driver;
+	store->name = nfstrdup( cfg->val );
 
 	while (getcline( cfg ) && cfg->cmd)
 		if (!strcasecmp( "Inbox", cfg->cmd ))
 			store->inbox = expand_strdup( cfg->val );
 		else if (!strcasecmp( "Path", cfg->cmd ))
-			store->gen.path = expand_strdup( cfg->val );
+			store->path = expand_strdup( cfg->val );
 #ifdef USE_DB
 		else if (!strcasecmp( "AltMap", cfg->cmd ))
 			store->alt_map = parse_bool( cfg );
@@ -1916,8 +1920,8 @@ maildir_parse_store( conffile_t *cfg, store_conf_t **storep )
 			parse_generic_store( &store->gen, cfg, "MaildirStore" );
 	if (!store->inbox)
 		store->inbox = expand_strdup( "~/Maildir" );
-	if (store->sub_style == SUB_MAILDIRPP && store->gen.path) {
-		error( "Maildir store '%s': Setting Path is incompatible with 'SubFolders Maildir++'\n", store->gen.name );
+	if (store->sub_style == SUB_MAILDIRPP && store->path) {
+		error( "Maildir store '%s': Setting Path is incompatible with 'SubFolders Maildir++'\n", store->name );
 		cfg->err = 1;
 	}
 	nfasprintf( &store->info_prefix, "%c2,", store->info_delimiter );
diff --git a/src/drv_proxy.c b/src/drv_proxy.c
index cd04bbd..82a3d0d 100644
--- a/src/drv_proxy.c
+++ b/src/drv_proxy.c
@@ -24,15 +24,18 @@
 #include <limits.h>
 #include <stdlib.h>
 
-typedef struct {
+typedef union proxy_store {
 	store_t gen;
-	const char *label; // foreign
-	uint ref_count;
-	driver_t *real_driver;
-	store_t *real_store;
+	struct {
+		STORE(union proxy_store)
+		const char *label;  // foreign
+		uint ref_count;
+		driver_t *real_driver;
+		store_t *real_store;
 
-	void (*bad_callback)( void *aux );
-	void *bad_callback_aux;
+		void (*bad_callback)( void *aux );
+		void *bad_callback_aux;
+	};
 } proxy_store_t;
 
 static void ATTR_PRINTFLIKE(1, 2)
@@ -81,10 +84,13 @@ proxy_store_deref( proxy_store_t *ctx )
 
 static int curr_tag;
 
-typedef struct {
-	uint ref_count;
-	int tag;
+#define GEN_CMD \
+	uint ref_count; \
+	int tag; \
 	proxy_store_t *ctx;
+
+typedef struct {
+	GEN_CMD
 } gen_cmd_t;
 
 static gen_cmd_t *
@@ -148,11 +154,14 @@ static @type@proxy_@name@( store_t *gctx@decl_args@ )
 //# END
 
 //# TEMPLATE CALLBACK
-typedef struct {
+typedef union {
 	gen_cmd_t gen;
-	void (*callback)( @decl_cb_args@void *aux );
-	void *callback_aux;
-	@decl_state@
+	struct {
+		GEN_CMD
+		void (*callback)( @decl_cb_args@void *aux );
+		void *callback_aux;
+		@decl_state@
+	};
 } @name@_cmd_t;
 
 static void
@@ -161,10 +170,10 @@ proxy_@name@_cb( @decl_cb_args@void *aux )
 	@name@_cmd_t *cmd = (@name@_cmd_t *)aux;
 
 	@pre_print_cb_args@
-	debug( "%s[% 2d] Callback enter @name@@print_fmt_cb_args@\n", cmd->gen.ctx->label, cmd->gen.tag@print_pass_cb_args@ );
+	debug( "%s[% 2d] Callback enter @name@@print_fmt_cb_args@\n", cmd->ctx->label, cmd->tag@print_pass_cb_args@ );
 	@print_cb_args@
 	cmd->callback( @pass_cb_args@cmd->callback_aux );
-	debug( "%s[% 2d] Callback leave @name@\n", cmd->gen.ctx->label, cmd->gen.tag );
+	debug( "%s[% 2d] Callback leave @name@\n", cmd->ctx->label, cmd->tag );
 	proxy_cmd_done( &cmd->gen );
 }
 
@@ -177,10 +186,10 @@ static @type@proxy_@name@( store_t *gctx@decl_args@, void (*cb)( @decl_cb_args@v
 	cmd->callback_aux = aux;
 	@assign_state@
 	@pre_print_args@
-	debug( "%s[% 2d] Enter @name@@print_fmt_args@\n", ctx->label, cmd->gen.tag@print_pass_args@ );
+	debug( "%s[% 2d] Enter @name@@print_fmt_args@\n", ctx->label, cmd->tag@print_pass_args@ );
 	@print_args@
 	ctx->real_driver->@name@( ctx->real_store@pass_args@, proxy_@name@_cb, cmd );
-	debug( "%s[% 2d] Leave @name@\n", ctx->label, cmd->gen.tag );
+	debug( "%s[% 2d] Leave @name@\n", ctx->label, cmd->tag );
 	proxy_cmd_done( &cmd->gen );
 }
 //# END
@@ -245,9 +254,9 @@ static @type@proxy_@name@( store_t *gctx@decl_args@, void (*cb)( @decl_cb_args@v
 //# DEFINE fetch_msg_print_pass_cb_args , fbuf, (long long)cmd->data->date, cmd->data->len
 //# DEFINE fetch_msg_print_cb_args
 	if (sts == DRV_OK && (DFlags & DEBUG_DRV_ALL)) {
-		printf( "%s=========\n", cmd->gen.ctx->label );
+		printf( "%s=========\n", cmd->ctx->label );
 		fwrite( cmd->data->data, cmd->data->len, 1, stdout );
-		printf( "%s=========\n", cmd->gen.ctx->label );
+		printf( "%s=========\n", cmd->ctx->label );
 		fflush( stdout );
 	}
 //# END
@@ -314,7 +323,7 @@ proxy_alloc_store( store_t *real_ctx, const char *label )
 	proxy_store_t *ctx;
 
 	ctx = nfcalloc( sizeof(*ctx) );
-	ctx->gen.driver = &proxy_driver;
+	ctx->driver = &proxy_driver;
 	ctx->gen.conf = real_ctx->conf;
 	ctx->ref_count = 1;
 	ctx->label = label;