Fix the bounds-checking code.

The code that set the bit within the select bitfield was correct, but the
bounds-checking code was not.  The change to that line uses the new _bitsize
macro for clarity.  Also, FD_ZERO macro did not zero-out anything but the
first word of the bitfield, so this could have caused problems with modules
using that macro with the expanded bitfield.

(closes issue #18773)
 Reported by: jamicque
 Patches: 
       20110423__issue18773.diff.txt uploaded by tilghman (license 14)
 Tested by: chris-mac


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@315501 65c4cc65-6c06-0410-ace0-fbb531ad65f3

include/asterisk/select.h

@@ -42,12 +42,14 @@ typedef struct {
 	TYPEOF_FD_SET_FDS_BITS fds_bits[ast_FDMAX / 8 / SIZEOF_FD_SET_FDS_BITS]; /* 32768 bits */
 } ast_fdset;
 
+#define _bitsize(a)	(sizeof(a) * 8)
+
 #undef FD_ZERO
 #define FD_ZERO(a) \
 	do { \
 		TYPEOF_FD_SET_FDS_BITS *bytes = (TYPEOF_FD_SET_FDS_BITS *) a; \
 		int i; \
-		for (i = 0; i < sizeof(*(a)) / SIZEOF_FD_SET_FDS_BITS; i++) { \
+		for (i = 0; i < ast_FDMAX / _bitsize(TYPEOF_FD_SET_FDS_BITS); i++) { \
 			bytes[i] = 0; \
 		} \
 	} while (0)
@@ -55,10 +57,12 @@ typedef struct {
 #define FD_SET(fd, fds) \
 	do { \
 		TYPEOF_FD_SET_FDS_BITS *bytes = (TYPEOF_FD_SET_FDS_BITS *) fds; \
-		if (fd / sizeof(*bytes) + ((fd + 1) % sizeof(*bytes) ? 1 : 0) < sizeof(*(fds))) { \
-			bytes[fd / (sizeof(*bytes) * 8)] |= ((TYPEOF_FD_SET_FDS_BITS) 1) << (fd % (sizeof(*bytes) * 8)); \
+		/* 32bit: FD / 32 + ((FD + 1) % 32 ? 1 : 0) < 1024 */ \
+		/* 64bit: FD / 64 + ((FD + 1) % 64 ? 1 : 0) < 512 */ \
+		if (fd / _bitsize(*bytes) + ((fd + 1) % _bitsize(*bytes) ? 1 : 0) < sizeof(*(fds)) / SIZEOF_FD_SET_FDS_BITS) { \
+			bytes[fd / _bitsize(*bytes)] |= ((TYPEOF_FD_SET_FDS_BITS) 1) << (fd % _bitsize(*bytes)); \
 		} else { \
-			ast_log(LOG_ERROR, "FD %d exceeds the maximum size of ast_fdset!\n", fd); \
+			fprintf(stderr, "FD %d exceeds the maximum size of ast_fdset!\n", fd); \
 		} \
 	} while (0)
 #endif /* HAVE_VARIABLE_FDSET */