Fix all warnings in the main codebase flagged by -Wsigned-compare

Remember, the code
   int is_less_than(int a, unsigned b) {
      return a < b;
   }
is buggy, since the C integer promotion rules basically turn it into
   int is_less_than(int a, unsigned b) {
      return ((unsigned)a) < b;
   }
and we really want something closer to
   int is_less_than(int a, unsigned b) {
      return a < 0 || ((unsigned)a) < b;
   }
.

Suggested by an example from Ralph Castain

arc4random.c

@@ -179,7 +179,8 @@ arc4_seed_sysctl_linux(void)
 	int mib[] = { CTL_KERN, KERN_RANDOM, RANDOM_UUID };
 	unsigned char buf[ADD_ENTROPY];
 	size_t len, n;
-	int i, any_set;
+	unsigned i;
+	int any_set;
 
 	memset(buf, 0, sizeof(buf));
 
@@ -190,7 +191,7 @@ arc4_seed_sysctl_linux(void)
 			return -1;
 	}
 	/* make sure that the buffer actually got set. */
-	for (i=any_set=0; i<sizeof(buf); ++i) {
+	for (i=0,any_set=0; i<sizeof(buf); ++i) {
 		any_set |= buf[i];
 	}
 	if (!any_set)

buffer.c

@@ -570,7 +570,7 @@ evbuffer_reserve_space(struct evbuffer *buf, ev_ssize_t size,
 
 		vec[0].iov_base = CHAIN_SPACE_PTR(chain);
 		vec[0].iov_len = CHAIN_SPACE_LEN(chain);
-		EVUTIL_ASSERT(vec[0].iov_len >= size);
+		EVUTIL_ASSERT(size<0 || vec[0].iov_len >= (size_t)size);
 		n = 1;
 	} else {
 		if (_evbuffer_expand_fast(buf, size, n_vecs)<0)
@@ -1934,7 +1934,7 @@ _evbuffer_read_setup_vecs(struct evbuffer *buf, ev_ssize_t howmuch,
 	}
 
 	chain = *firstchainp;
-	for (i = 0; i < n_vecs_avail && so_far < howmuch; ++i) {
+	for (i = 0; i < n_vecs_avail && so_far < (size_t)howmuch; ++i) {
 		size_t avail = CHAIN_SPACE_LEN(chain);
 		if (avail > (howmuch - so_far) && exact)
 			avail = howmuch - so_far;
@@ -2252,7 +2252,7 @@ evbuffer_write_atmost(struct evbuffer *buffer, evutil_socket_t fd,
 		goto done;
 	}
 
-	if (howmuch < 0 || howmuch > buffer->total_len)
+	if (howmuch < 0 || (size_t)howmuch > buffer->total_len)
 		howmuch = buffer->total_len;
 
 	if (howmuch > 0) {
@@ -2420,7 +2420,7 @@ evbuffer_search_range(struct evbuffer *buffer, const char *what, size_t len, con
 	if (end)
 		last_chain = end->_internal.chain;
 
-	if (!len)
+	if (!len || len > EV_SSIZE_MAX)
 		goto done;
 
 	first = what[0];
@@ -2435,7 +2435,7 @@ evbuffer_search_range(struct evbuffer *buffer, const char *what, size_t len, con
 			pos.pos += p - start_at;
 			pos._internal.pos_in_chain += p - start_at;
 			if (!evbuffer_ptr_memcmp(buffer, &pos, what, len)) {
-				if (end && pos.pos + len > end->pos)
+				if (end && pos.pos + (ev_ssize_t)len > end->pos)
 					goto not_found;
 				else
 					goto done;

bufferevent-internal.h

@@ -91,7 +91,7 @@ struct bufferevent_rate_limit_group {
 
 	/** The smallest number of bytes that any member of the group should
 	 * be limited to read or write at a time. */
-	ev_uint32_t min_share;
+	ev_int32_t min_share;
 	/** Timeout event that goes off once a tick, when the bucket is ready
 	 * to refill. */
 	struct event master_refill_event;

bufferevent_ratelim.c

@@ -56,9 +56,9 @@ ev_token_bucket_init(struct ev_token_bucket *bucket,
 		   leave "last_updated" as it is; the next update will add the
 		   appropriate amount of bandwidth to the bucket.
 		*/
-		if (bucket->read_limit > cfg->read_maximum)
+		if (bucket->read_limit > (ev_int64_t) cfg->read_maximum)
 			bucket->read_limit = cfg->read_maximum;
-		if (bucket->write_limit > cfg->write_maximum)
+		if (bucket->write_limit > (ev_int64_t) cfg->write_maximum)
 			bucket->write_limit = cfg->write_maximum;
 	} else {
 		bucket->read_limit = cfg->read_rate;
@@ -221,7 +221,7 @@ _bufferevent_get_rlim_max(struct bufferevent_private *bev, int is_write)
 	if (bev->rate_limiting->group) {
 		struct bufferevent_rate_limit_group *g =
 		    bev->rate_limiting->group;
-		ev_uint32_t share;
+		ev_int32_t share;
 		LOCK_GROUP(g);
 		if (GROUP_SUSPENDED(g)) {
 			/* We can get here if we failed to lock this
@@ -632,9 +632,9 @@ bufferevent_rate_limit_group_set_cfg(
 		&g->rate_limit_cfg.tick_timeout, &cfg->tick_timeout, ==);
 	memcpy(&g->rate_limit_cfg, cfg, sizeof(g->rate_limit_cfg));
 
-	if (g->rate_limit.read_limit > cfg->read_maximum)
+	if (g->rate_limit.read_limit > (ev_int32_t)cfg->read_maximum)
 		g->rate_limit.read_limit = cfg->read_maximum;
-	if (g->rate_limit.write_limit > cfg->write_maximum)
+	if (g->rate_limit.write_limit > (ev_int32_t)cfg->write_maximum)
 		g->rate_limit.write_limit = cfg->write_maximum;
 
 	if (!same_tick) {
@@ -651,6 +651,9 @@ bufferevent_rate_limit_group_set_min_share(
 	struct bufferevent_rate_limit_group *g,
 	size_t share)
 {
+	if (share > EV_INT32_MAX)
+		return -1;
+
 	g->min_share = share;
 	return 0;
 }

evdns.c

@@ -3900,7 +3900,7 @@ evdns_base_parse_hosts_line(struct evdns_base *base, char *line)
 	memset(&ss, 0, sizeof(ss));
 	if (evutil_parse_sockaddr_port(addr, (struct sockaddr*)&ss, &socklen)<0)
 		return -1;
-	if (socklen > sizeof(struct sockaddr_in6))
+	if (socklen > (int)sizeof(struct sockaddr_in6))
 		return -1;
 
 	if (sockaddr_getport((struct sockaddr*)&ss))
@@ -3920,7 +3920,7 @@ evdns_base_parse_hosts_line(struct evdns_base *base, char *line)
 		he = mm_calloc(1, sizeof(struct hosts_entry)+namelen);
 		if (!he)
 			return -1;
-		EVUTIL_ASSERT(socklen <= sizeof(he->addr));
+		EVUTIL_ASSERT(socklen <= (int)sizeof(he->addr));
 		memcpy(&he->addr, &ss, socklen);
 		memcpy(he->hostname, hostname, namelen+1);
 		he->addrlen = socklen;

event_tagging.c

@@ -194,9 +194,10 @@ static int
 decode_tag_internal(ev_uint32_t *ptag, struct evbuffer *evbuf, int dodrain)
 {
 	ev_uint32_t number = 0;
-	int len = evbuffer_get_length(evbuf);
+	size_t len = evbuffer_get_length(evbuf);
 	ev_uint8_t *data;
-	int count = 0, shift = 0, done = 0;
+	size_t count = 0;
+	int  shift = 0, done = 0;
 
 	/*
 	 * the encoding of a number is at most one byte more than its
@@ -225,7 +226,7 @@ decode_tag_internal(ev_uint32_t *ptag, struct evbuffer *evbuf, int dodrain)
 	if (ptag != NULL)
 		*ptag = number;
 
-	return (count);
+	return count > INT_MAX ? INT_MAX : (int)(count);
 }
 
 int
@@ -524,11 +525,11 @@ evtag_unmarshal_fixed(struct evbuffer *src, ev_uint32_t need_tag, void *data,
 	int tag_len;
 
 	/* Now unmarshal a tag and check that it matches the tag we want */
-	if ((tag_len = evtag_unmarshal_header(src, &tag)) == -1 ||
+	if ((tag_len = evtag_unmarshal_header(src, &tag)) < 0 ||
 	    tag != need_tag)
 		return (-1);
 
-	if (tag_len != len)
+	if ((size_t)tag_len != len)
 		return (-1);
 
 	evbuffer_remove(src, data, len);

evutil.c

@@ -119,7 +119,8 @@ evutil_read_file(const char *filename, char **content_out, size_t *len_out,
 	fd = open(filename, mode);
 	if (fd < 0)
 		return -1;
-	if (fstat(fd, &st)) {
+	if (fstat(fd, &st) || st.st_size < 0 ||
+	    st.st_size > EV_SSIZE_MAX-1 ) {
 		close(fd);
 		return -2;
 	}
@@ -131,9 +132,9 @@ evutil_read_file(const char *filename, char **content_out, size_t *len_out,
 	read_so_far = 0;
 	while ((r = read(fd, mem+read_so_far, st.st_size - read_so_far)) > 0) {
 		read_so_far += r;
-		if (read_so_far >= st.st_size)
+		if (read_so_far >= (size_t)st.st_size)
 			break;
-		EVUTIL_ASSERT(read_so_far < st.st_size);
+		EVUTIL_ASSERT(read_so_far < (size_t)st.st_size);
 	}
 	close(fd);
 	if (r < 0) {
@@ -1766,7 +1767,7 @@ evutil_parse_sockaddr_port(const char *ip_as_string, struct sockaddr *out, int *
 		sin6.sin6_port = htons(port);
 		if (1 != evutil_inet_pton(AF_INET6, addr_part, &sin6.sin6_addr))
 			return -1;
-		if (sizeof(sin6) > *outlen)
+		if ((int)sizeof(sin6) > *outlen)
 			return -1;
 		memset(out, 0, *outlen);
 		memcpy(out, &sin6, sizeof(sin6));
@@ -1785,7 +1786,7 @@ evutil_parse_sockaddr_port(const char *ip_as_string, struct sockaddr *out, int *
 		sin.sin_port = htons(port);
 		if (1 != evutil_inet_pton(AF_INET, addr_part, &sin.sin_addr))
 			return -1;
-		if (sizeof(sin) > *outlen)
+		if ((int)sizeof(sin) > *outlen)
 			return -1;
 		memset(out, 0, *outlen);
 		memcpy(out, &sin, sizeof(sin));

http.c

@@ -844,7 +844,7 @@ evhttp_read_body(struct evhttp_connection *evcon, struct evhttp_request *req)
 		evbuffer_add_buffer(req->input_buffer, buf);
 		req->body_size += evbuffer_get_length(buf);
 	} else if (req->chunk_cb != NULL ||
-	    evbuffer_get_length(buf) >= req->ntoread) {
+	    evbuffer_get_length(buf) >= (size_t)req->ntoread) {
 		/* We've postponed moving the data until now, but we're
 		 * about to use it. */
 		req->ntoread -= evbuffer_get_length(buf);
@@ -2251,11 +2251,11 @@ evhttp_response_phrase_internal(int code)
 	int subcode = code % 100;
 
 	/* Unknown class - can't do any better here */
-	if (klass < 0 || klass >= MEMBERSOF(response_classes))
+	if (klass < 0 || klass >= (int) MEMBERSOF(response_classes))
 		return "Unknown Status Class";
 
 	/* Unknown sub-code, return class name at least */
-	if (subcode >= response_classes[klass].num_responses)
+	if (subcode >= (int) response_classes[klass].num_responses)
 		return response_classes[klass].name;
 
 	return response_classes[klass].responses[subcode];

log-internal.h

@@ -37,7 +37,7 @@
 #define EV_NORETURN
 #endif
 
-#define _EVENT_ERR_ABORT 0xdeaddead
+#define _EVENT_ERR_ABORT ((int)0xdeaddead)
 
 void event_err(int eval, const char *fmt, ...) EV_CHECK_FMT(2,3) EV_NORETURN;
 void event_warn(const char *fmt, ...) EV_CHECK_FMT(1,2);

minheap-internal.h

@@ -95,7 +95,7 @@ int min_heap_elt_is_top(const struct event *e)
 
 int min_heap_erase(min_heap_t* s, struct event* e)
 {
-	if (((unsigned int)-1) != e->ev_timeout_pos.min_heap_idx)
+	if (-1 != e->ev_timeout_pos.min_heap_idx)
 	{
 		struct event *last = s->p[--s->n];
 		unsigned parent = (e->ev_timeout_pos.min_heap_idx - 1) / 2;

select.c

@@ -234,11 +234,14 @@ select_add(struct event_base *base, int fd, short old, short events, void *p)
 	if (sop->event_fds < fd) {
 		int fdsz = sop->event_fdsz;
 
-		if (fdsz < sizeof(fd_mask))
-			fdsz = sizeof(fd_mask);
+		if (fdsz < (int)sizeof(fd_mask))
+			fdsz = (int)sizeof(fd_mask);
 
+		/* In theory we should worry about overflow here.  In
+		 * reality, though, the highest fd on a unixy system will
+		 * not overflow here. XXXX */
 		while (fdsz <
-		    (howmany(fd + 1, NFDBITS) * sizeof(fd_mask)))
+		    (int) (howmany(fd + 1, NFDBITS) * sizeof(fd_mask)))
 			fdsz *= 2;
 
 		if (fdsz != sop->event_fdsz) {