build(flags): preserve flag-value ABI by pinning new flags to high bits

dist/api_flags

@@ -213,7 +213,7 @@ DbEnv.set_flags
 	DB_DIRECT_DB			# Don't buffer databases in the OS
 	DB_DSYNC_DB			# Set O_DSYNC on the databases
 	DB_HOTBACKUP_IN_PROGRESS	# Inhibit bulk loading optimization
-	DB_MPOOL_AIO			# Use asynchronous buffer-pool writeback
+	DB_MPOOL_AIO		__PIN=0x00100000	# Use asynchronous buffer-pool writeback
 	DB_MULTIVERSION			# Multiversion concurrency control
 	DB_NOLOCKING			# Set locking/mutex behavior
 	DB_NOMMAP			# Don't mmap the underlying file
@@ -276,7 +276,7 @@ DbEnv.txn_begin
 	DB_TXN_FAMILY			# Cursors and child txns are
 					# independent but lock-compatible
 	DB_TXN_SNAPSHOT			# Snapshot isolation
-	DB_TXN_SNAPSHOT_SAFE		# Serializable snapshot isolation (SSI)
+	DB_TXN_SNAPSHOT_SAFE	__PIN=0x00000800	# Serializable snapshot isolation (SSI)
 	DB_TXN_SYNC			# Always sync log on commit
 	DB_TXN_WAIT			# Always wait for locks in this txn
 	DB_TXN_WRITE_NOSYNC		# Write the log but don't sync

dist/api_flags.c

@@ -27,13 +27,14 @@ typedef struct {
 	API	**api, **api_end;
 
 	u_int	value;			/* Bit value */
+	int	pinned;			/* Value was pinned via __PIN= */
 } FLAG;
 FLAG	**flag_list, **flag_end;
 
 int	verbose;
 char	*progname;
 
-int	add_entry(char *, char *);
+int	add_entry(char *, char *, u_int);
 void	define_print(char *, u_int);
 void	dump_api(void);
 void	dump_flags(void);
@@ -129,16 +130,43 @@ parse()
 		 * with leading whitespace is a flag name.
 		 */
 		if (isspace(buf[0])) {
-			if ((p = strtok(buf, " \t")) == NULL || *p == '#')
+			char *flag, *extra;
+			u_int pin;
+
+			if ((flag = strtok(buf, " \t")) == NULL || *flag == '#')
 				continue;
 
 			/* A flag without an API makes no sense. */
 			if (api == NULL)
 				goto format;
 
+			/*
+			 * An optional "__PIN=<value>" token after a flag name
+			 * forces that flag to a fixed bit and reserves the bit
+			 * from the API's greedy allocation.  This lets new
+			 * flags take high, unused bits without renumbering the
+			 * existing public flag values (preserving the ABI of
+			 * the generated constants).
+			 */
+			pin = 0;
+			if ((extra = strtok(NULL, " \t")) != NULL &&
+			    *extra != '#') {
+				if (strncmp(extra,
+				    "__PIN=", sizeof("__PIN=") - 1) != 0)
+					goto format;
+				pin = (u_int)strtoul(
+				    extra + sizeof("__PIN=") - 1, NULL, 0);
+				if (pin == 0)
+					goto format;
+				if ((extra = strtok(NULL, " \t")) != NULL &&
+				    *extra != '#')
+					goto format;
+			}
+
 			/* Enter the pair into the array. */
-			if (add_entry(api, p))
+			if (add_entry(api, flag, pin))
 				return (1);
+			continue;
 		} else {
 			if ((p = strtok(buf, " \t")) == NULL)
 				continue;
@@ -158,7 +186,7 @@ format:	fprintf(stderr, "%s: format error: line %d\n", progname, lc);
 }
 
 int
-add_entry(char *api_name, char *flag_name)
+add_entry(char *api_name, char *flag_name, u_int pin)
 {
 	FLAG **fpp, *fp;
 	API **app, *ap, **p;
@@ -225,6 +253,12 @@ add_entry(char *api_name, char *flag_name)
 	fp = *fpp;
 	++fp->api_cnt;
 
+	/* Record an explicit pinned bit value, if given. */
+	if (pin != 0) {
+		fp->value = pin;
+		fp->pinned = 1;
+	}
+
 	/* Check to see if this API is already listed for this flag. */
 	for (p = fp->api; p != NULL && *p != NULL && p < fp->api_end; ++p)
 		if (strcmp(api_name, (*p)->name) == 0) {
@@ -313,12 +347,34 @@ generate_flags()
 	qsort(flag_list,
 	    (u_int)(flag_end - flag_list), sizeof(FLAG *), flag_cmp_api_cnt);
 
+	/*
+	 * Reserve every pinned flag's fixed bit in each API that uses it,
+	 * before the greedy pass, so the greedy allocator never hands that
+	 * bit to another flag.  Pinned flags keep their explicit value and
+	 * are skipped below.
+	 */
+	for (fpp = flag_list; *fpp != NULL; ++fpp) {
+		if (!(*fpp)->pinned)
+			continue;
+		for (api = (*fpp)->api; *api != NULL; ++api) {
+			if ((*api)->used_mask & (*fpp)->value) {
+				fprintf(stderr,
+		    "%s: pinned bit %#x for flag %s already in use\n",
+				    progname, (*fpp)->value, (*fpp)->name);
+				return (1);
+			}
+			(*api)->used_mask |= (*fpp)->value;
+		}
+	}
+
 	/*
 	 * Here's the plan: walk the list of flags, allocating bits.  For
 	 * each flag, we walk the list of APIs that use it and find a bit
 	 * none of them are using.  That bit becomes the flag's value.
 	 */
 	for (fpp = flag_list; *fpp != NULL; ++fpp) {
+		if ((*fpp)->pinned)		/* already assigned */
+			continue;
 		mask = 0xffffffff;			/* Set to all 1's */
 		for (api = (*fpp)->api; *api != NULL; ++api)
 			mask &= ~(*api)->used_mask;	/* Clear API's bits */

lang/csharp/src/Internal/DbConstants.cs

@@ -158,19 +158,19 @@ internal class DbConstants {
         internal const uint DB_NEXT_DUP = 17;
         internal const uint DB_NEXT_NODUP = 18;
         internal const uint DB_NODUPDATA = 19;
-        internal const uint DB_NOLOCKING = 0x00004000;
+        internal const uint DB_NOLOCKING = 0x00002000;
         internal const uint DB_NOMMAP = 0x00000010;
         internal const uint DB_NOORDERCHK = 0x00000002;
         internal const uint DB_NOOVERWRITE = 20;
-        internal const uint DB_NOPANIC = 0x00008000;
+        internal const uint DB_NOPANIC = 0x00004000;
         internal const int DB_NOSERVER = -30989;
         internal const uint DB_NOSYNC = 0x00000001;
         internal const int DB_NOTFOUND = -30988;
         internal const int DB_OLD_VERSION = -30987;
         internal const uint DB_ORDERCHKONLY = 0x00000004;
-        internal const uint DB_OVERWRITE = 0x00010000;
+        internal const uint DB_OVERWRITE = 0x00008000;
         internal const int DB_PAGE_NOTFOUND = -30986;
-        internal const uint DB_PANIC_ENVIRONMENT = 0x00020000;
+        internal const uint DB_PANIC_ENVIRONMENT = 0x00010000;
         internal const uint DB_POSITION = 22;
         internal const uint DB_PREV = 23;
         internal const uint DB_PREV_DUP = 24;
@@ -190,7 +190,7 @@ internal class DbConstants {
         internal const uint DB_RECNUM = 0x00000040;
         internal const uint DB_RECOVER = 0x00000002;
         internal const uint DB_RECOVER_FATAL = 0x00020000;
-        internal const uint DB_REGION_INIT = 0x00040000;
+        internal const uint DB_REGION_INIT = 0x00020000;
         internal const uint DB_REGISTER = 0x00040000;
         internal const uint DB_RENUMBER = 0x00000080;
         internal const int DB_REPMGR_ACKS_ALL = 1;
@@ -265,7 +265,7 @@ internal class DbConstants {
         internal const uint DB_SYSTEM_MEM = 0x00080000;
         internal const uint DB_THREAD = 0x00000020;
         internal const int DB_TIMEOUT = -30971;
-        internal const uint DB_TIME_NOTGRANTED = 0x00080000;
+        internal const uint DB_TIME_NOTGRANTED = 0x00040000;
         internal const uint DB_TRUNCATE = 0x00020000;
         internal const uint DB_TXN_ABORT = 0;
         internal const uint DB_TXN_APPLY = 1;
@@ -279,7 +279,7 @@ internal class DbConstants {
         internal const uint DB_TXN_SNAPSHOT = 0x00000004;
         internal const uint DB_TXN_SYNC = 0x00000008;
         internal const uint DB_TXN_TOKEN_SIZE = 20;
-        internal const uint DB_TXN_WAIT = 0x00000100;
+        internal const uint DB_TXN_WAIT = 0x00000080;
         internal const uint DB_TXN_WRITE_NOSYNC = 0x00000020;
         internal const uint DB_UNKNOWN = 5;
         internal const uint DB_UPGRADE = 0x00000001;
@@ -318,7 +318,7 @@ internal class DbConstants {
         internal const string DB_VERSION_STRING = "Berkeley DB 5.3.29: September 9 2013 ";
         internal const string DB_VERSION_FULL_STRING = "Berkeley DB 11g Release 2 library version 11.2.5.3.29: September 9 2013 ";
         internal const uint DB_WRITECURSOR = 0x00000010;
-        internal const uint DB_YIELDCPU = 0x00100000;
+        internal const uint DB_YIELDCPU = 0x00080000;
         internal const uint DB_USERCOPY_GETDATA = 0x00000001;
         internal const uint DB_USERCOPY_SETDATA = 0x00000002;
     }

lang/java/src/com/sleepycat/db/internal/DbConstants.java

@@ -129,16 +129,16 @@ public interface DbConstants
     int DB_NEXT_DUP = 17;
     int DB_NEXT_NODUP = 18;
     int DB_NODUPDATA = 19;
-    int DB_NOLOCKING = 0x00004000;
+    int DB_NOLOCKING = 0x00002000;
     int DB_NOMMAP = 0x00000010;
     int DB_NOORDERCHK = 0x00000002;
     int DB_NOOVERWRITE = 20;
-    int DB_NOPANIC = 0x00008000;
+    int DB_NOPANIC = 0x00004000;
     int DB_NOSYNC = 0x00000001;
     int DB_NOTFOUND = -30988;
     int DB_ORDERCHKONLY = 0x00000004;
-    int DB_OVERWRITE = 0x00010000;
-    int DB_PANIC_ENVIRONMENT = 0x00020000;
+    int DB_OVERWRITE = 0x00008000;
+    int DB_PANIC_ENVIRONMENT = 0x00010000;
     int DB_POSITION = 22;
     int DB_PREV = 23;
     int DB_PREV_DUP = 24;
@@ -158,7 +158,7 @@ public interface DbConstants
     int DB_RECNUM = 0x00000040;
     int DB_RECOVER = 0x00000002;
     int DB_RECOVER_FATAL = 0x00020000;
-    int DB_REGION_INIT = 0x00040000;
+    int DB_REGION_INIT = 0x00020000;
     int DB_REGISTER = 0x00040000;
     int DB_RENUMBER = 0x00000080;
     int DB_REPMGR_ACKS_ALL = 1;
@@ -218,7 +218,7 @@ public interface DbConstants
     int DB_SYSTEM_MEM = 0x00080000;
     int DB_THREAD = 0x00000020;
     int DB_TIMEOUT = -30971;
-    int DB_TIME_NOTGRANTED = 0x00080000;
+    int DB_TIME_NOTGRANTED = 0x00040000;
     int DB_TRUNCATE = 0x00020000;
     int DB_TXN_ABORT = 0;
     int DB_TXN_APPLY = 1;
@@ -232,7 +232,7 @@ public interface DbConstants
     int DB_TXN_SNAPSHOT = 0x00000004;
     int DB_TXN_SYNC = 0x00000008;
     int DB_TXN_TOKEN_SIZE = 20;
-    int DB_TXN_WAIT = 0x00000100;
+    int DB_TXN_WAIT = 0x00000080;
     int DB_TXN_WRITE_NOSYNC = 0x00000020;
     int DB_UNKNOWN = 5;
     int DB_UPGRADE = 0x00000001;
@@ -260,7 +260,7 @@ public interface DbConstants
     int DB_VERSION_MINOR = 3;
     int DB_VERSION_PATCH = 29;
     int DB_WRITECURSOR = 0x00000010;
-    int DB_YIELDCPU = 0x00100000;
+    int DB_YIELDCPU = 0x00080000;
 }
 
 // end of DbConstants.java