diff --git a/proxy.c b/proxy.c
index 0aa9cf35..d0bf2a82 100644
--- a/proxy.c
+++ b/proxy.c
@@ -1276,15 +1276,8 @@ int proxy_socks5_negotiate (ProxySocket *p, int change)
 char *format_telnet_command(SockAddr *addr, int port, Conf *conf)
 {
     char *fmt = conf_get_str(conf, CONF_proxy_telnet_command);
-    char *ret = NULL;
-    int retlen = 0, retsize = 0;
     int so = 0, eo = 0;
-#define ENSURE(n) do { \
-    if (retsize < retlen + n) { \
-	retsize = retlen + n + 512; \
-	ret = sresize(ret, retsize, char); \
-    } \
-} while (0)
+    strbuf *buf = strbuf_new();
 
     /* we need to escape \\, \%, \r, \n, \t, \x??, \0???, 
      * %%, %host, %port, %user, and %pass
@@ -1302,11 +1295,8 @@ char *format_telnet_command(SockAddr *addr, int port, Conf *conf)
 
 	/* if there was any unescaped text before the escape
 	 * character, send that now */
-	if (eo != so) {
-	    ENSURE(eo - so);
-	    memcpy(ret + retlen, fmt + so, eo - so);
-	    retlen += eo - so;
-	}
+	if (eo != so)
+            put_data(buf, fmt + so, eo - so);
 
 	so = eo++;
 
@@ -1323,32 +1313,27 @@ char *format_telnet_command(SockAddr *addr, int port, Conf *conf)
 	    switch (fmt[eo]) {
 
 	      case '\\':
-		ENSURE(1);
-		ret[retlen++] = '\\';
+		put_byte(buf, '\\');
 		eo++;
 		break;
 
 	      case '%':
-		ENSURE(1);
-		ret[retlen++] = '%';
+                put_byte(buf, '%');
 		eo++;
 		break;
 
 	      case 'r':
-		ENSURE(1);
-		ret[retlen++] = '\r';
+                put_byte(buf, '\r');
 		eo++;
 		break;
 
 	      case 'n':
-		ENSURE(1);
-		ret[retlen++] = '\n';
+                put_byte(buf, '\n');
 		eo++;
 		break;
 
 	      case 't':
-		ENSURE(1);
-		ret[retlen++] = '\t';
+                put_byte(buf, '\t');
 		eo++;
 		break;
 
@@ -1371,16 +1356,14 @@ char *format_telnet_command(SockAddr *addr, int port, Conf *conf)
 			    /* non hex character, so we abort and just
 			     * send the whole thing unescaped (including \x)
 			     */
-			    ENSURE(1);
-			    ret[retlen++] = '\\';
+                            put_byte(buf, '\\');
 			    eo = so + 1;
 			    break;
 			}
 
 			/* we only extract two hex characters */
 			if (i == 1) {
-			    ENSURE(1);
-			    ret[retlen++] = v;
+                            put_byte(buf, v);
 			    eo++;
 			    break;
 			}
@@ -1392,9 +1375,7 @@ char *format_telnet_command(SockAddr *addr, int port, Conf *conf)
 		break;
 
 	      default:
-		ENSURE(2);
-		memcpy(ret+retlen, fmt + so, 2);
-		retlen += 2;
+                put_data(buf, fmt + so, 2);
 		eo++;
 		break;
 	    }
@@ -1406,61 +1387,37 @@ char *format_telnet_command(SockAddr *addr, int port, Conf *conf)
 	     */
 
 	    if (fmt[eo] == '%') {
-		ENSURE(1);
-		ret[retlen++] = '%';
+                put_byte(buf, '%');
 		eo++;
 	    }
 	    else if (strnicmp(fmt + eo, "host", 4) == 0) {
 		char dest[512];
-		int destlen;
 		sk_getaddr(addr, dest, lenof(dest));
-		destlen = strlen(dest);
-		ENSURE(destlen);
-		memcpy(ret+retlen, dest, destlen);
-		retlen += destlen;
+		put_data(buf, dest, strlen(dest));
 		eo += 4;
 	    }
 	    else if (strnicmp(fmt + eo, "port", 4) == 0) {
-		char portstr[8], portlen;
-		portlen = sprintf(portstr, "%i", port);
-		ENSURE(portlen);
-		memcpy(ret + retlen, portstr, portlen);
-		retlen += portlen;
+                strbuf_catf(buf, "%d", port);
 		eo += 4;
 	    }
 	    else if (strnicmp(fmt + eo, "user", 4) == 0) {
-		char *username = conf_get_str(conf, CONF_proxy_username);
-		int userlen = strlen(username);
-		ENSURE(userlen);
-		memcpy(ret+retlen, username, userlen);
-		retlen += userlen;
+		const char *username = conf_get_str(conf, CONF_proxy_username);
+		put_data(buf, username, strlen(username));
 		eo += 4;
 	    }
 	    else if (strnicmp(fmt + eo, "pass", 4) == 0) {
-		char *password = conf_get_str(conf, CONF_proxy_password);
-		int passlen = strlen(password);
-		ENSURE(passlen);
-		memcpy(ret+retlen, password, passlen);
-		retlen += passlen;
+		const char *password = conf_get_str(conf, CONF_proxy_password);
+		put_data(buf, password, strlen(password));
 		eo += 4;
 	    }
 	    else if (strnicmp(fmt + eo, "proxyhost", 9) == 0) {
-		char *host = conf_get_str(conf, CONF_proxy_host);
-		int phlen = strlen(host);
-		ENSURE(phlen);
-		memcpy(ret+retlen, host, phlen);
-		retlen += phlen;
+		const char *host = conf_get_str(conf, CONF_proxy_host);
+		put_data(buf, host, strlen(host));
 		eo += 9;
 	    }
 	    else if (strnicmp(fmt + eo, "proxyport", 9) == 0) {
 		int port = conf_get_int(conf, CONF_proxy_port);
-                char pport[50];
-		int pplen;
-                sprintf(pport, "%d", port);
-                pplen = strlen(pport);
-		ENSURE(pplen);
-		memcpy(ret+retlen, pport, pplen);
-		retlen += pplen;
+                strbuf_catf(buf, "%d", port);
 		eo += 9;
 	    }
 	    else {
@@ -1468,8 +1425,7 @@ char *format_telnet_command(SockAddr *addr, int port, Conf *conf)
 		 * don't advance eo, so that we'll consider the
 		 * text immediately following the % as unescaped.
 		 */
-		ENSURE(1);
-		ret[retlen++] = '%';
+                put_byte(buf, '%');
 	    }
 	}
 
@@ -1479,16 +1435,10 @@ char *format_telnet_command(SockAddr *addr, int port, Conf *conf)
 
     /* if there is any unescaped text at the end of the line, send it */
     if (eo != so) {
-	ENSURE(eo - so);
-	memcpy(ret + retlen, fmt + so, eo - so);
-	retlen += eo - so;
+	put_data(buf, fmt + so, eo - so);
     }
 
-    ENSURE(1);
-    ret[retlen] = '\0';
-    return ret;
-
-#undef ENSURE
+    return strbuf_to_str(buf);
 }
 
 int proxy_telnet_negotiate (ProxySocket *p, int change)
diff --git a/unix/gtkdlg.c b/unix/gtkdlg.c
index 84f9774f..16ba1371 100644
--- a/unix/gtkdlg.c
+++ b/unix/gtkdlg.c
@@ -3763,7 +3763,7 @@ struct eventlog_stuff {
     char **events_initial;
     char **events_circular;
     int ninitial, ncircular, circular_first;
-    char *seldata;
+    strbuf *seldata;
     int sellen;
     bool ignore_selchange;
 };
@@ -3773,8 +3773,6 @@ static void eventlog_destroy(GtkWidget *widget, gpointer data)
     eventlog_stuff *es = (eventlog_stuff *)data;
 
     es->window = NULL;
-    sfree(es->seldata);
-    es->seldata = NULL;
     dlg_cleanup(&es->dp);
     ctrl_free_box(es->eventbox);
 }
@@ -3803,7 +3801,6 @@ static void eventlog_list_handler(union control *ctrl, dlgparam *dp,
         dlg_update_done(ctrl, dp);
     } else if (event == EVENT_SELCHANGE) {
         int i;
-        int selsize = 0;
 
         /*
          * If this SELCHANGE event is happening as a result of
@@ -3817,36 +3814,15 @@ static void eventlog_list_handler(union control *ctrl, dlgparam *dp,
         /*
          * Construct the data to use as the selection.
          */
-        sfree(es->seldata);
-        es->seldata = NULL;
-        es->sellen = 0;
+        es->seldata->len = 0;
         for (i = 0; i < es->ninitial; i++) {
-            if (dlg_listbox_issel(ctrl, dp, i)) {
-                int extralen = strlen(es->events_initial[i]);
-
-                if (es->sellen + extralen + 2 > selsize) {
-                    selsize = es->sellen + extralen + 512;
-                    es->seldata = sresize(es->seldata, selsize, char);
-                }
-
-                strcpy(es->seldata + es->sellen, es->events_initial[i]);
-                es->sellen += extralen;
-                es->seldata[es->sellen++] = '\n';
-            }
+            if (dlg_listbox_issel(ctrl, dp, i))
+                strbuf_catf(es->seldata, "%s\n", es->events_initial[i]);
         }
         for (i = 0; i < es->ncircular; i++) {
             if (dlg_listbox_issel(ctrl, dp, es->ninitial + i)) {
                 int j = (es->circular_first + i) % LOGEVENT_CIRCULAR_MAX;
-                int extralen = strlen(es->events_circular[j]);
-
-                if (es->sellen + extralen + 2 > selsize) {
-                    selsize = es->sellen + extralen + 512;
-                    es->seldata = sresize(es->seldata, selsize, char);
-                }
-
-                strcpy(es->seldata + es->sellen, es->events_circular[j]);
-                es->sellen += extralen;
-                es->seldata[es->sellen++] = '\n';
+                strbuf_catf(es->seldata, "%s\n", es->events_circular[j]);
             }
         }
 
@@ -3867,7 +3843,7 @@ void eventlog_selection_get(GtkWidget *widget, GtkSelectionData *seldata,
     eventlog_stuff *es = (eventlog_stuff *)data;
 
     gtk_selection_data_set(seldata, gtk_selection_data_get_target(seldata), 8,
-                           (unsigned char *)es->seldata, es->sellen);
+                           es->seldata->u, es->seldata->len);
 }
 
 gint eventlog_selection_clear(GtkWidget *widget, GdkEventSelection *seldata,
@@ -3891,9 +3867,6 @@ gint eventlog_selection_clear(GtkWidget *widget, GdkEventSelection *seldata,
 #endif
     es->ignore_selchange = false;
 
-    sfree(es->seldata);
-    es->sellen = 0;
-    es->seldata = NULL;
     return true;
 }
 
@@ -3983,6 +3956,7 @@ eventlog_stuff *eventlogstuff_new(void)
 {
     eventlog_stuff *es = snew(eventlog_stuff);
     memset(es, 0, sizeof(*es));
+    es->seldata = strbuf_new();
     return es;
 }
 
@@ -4000,6 +3974,7 @@ void eventlogstuff_free(eventlog_stuff *es)
             sfree(es->events_circular[i]);
         sfree(es->events_circular);
     }
+    strbuf_free(es->seldata);
 
     sfree(es);
 }
diff --git a/unix/gtkfont.c b/unix/gtkfont.c
index ad29034e..a685884b 100644
--- a/unix/gtkfont.c
+++ b/unix/gtkfont.c
@@ -1882,8 +1882,7 @@ static void pangofont_enum_fonts(GtkWidget *widget, fontsel_add_entry callback,
 	     * If so, go through them one by one.
 	     */
 	    for (k = 0; k < nsizes; k++) {
-		char *fullname;
-		char stylekey[128];
+		char *fullname, *stylekey;
 
 		pango_font_description_set_size(desc, sizes[k]);
 
@@ -1893,27 +1892,27 @@ static void pangofont_enum_fonts(GtkWidget *widget, fontsel_add_entry callback,
 		 * Construct the sorting key for font styles.
 		 */
 		{
-		    char *p = stylekey;
-		    int n;
+                    strbuf *buf = strbuf_new();
 
-		    n = pango_font_description_get_weight(desc);
+		    int weight = pango_font_description_get_weight(desc);
 		    /* Weight: normal, then lighter, then bolder */
-		    if (n <= PANGO_WEIGHT_NORMAL)
-			n = PANGO_WEIGHT_NORMAL - n;
-		    p += sprintf(p, "%4d", n);
+		    if (weight <= PANGO_WEIGHT_NORMAL)
+			weight = PANGO_WEIGHT_NORMAL - weight;
+		    strbuf_catf(buf, "%4d", weight);
 
-		    n = pango_font_description_get_style(desc);
-		    p += sprintf(p, " %2d", n);
+		    strbuf_catf(buf, " %2d",
+                                pango_font_description_get_style(desc));
 
-		    n = pango_font_description_get_stretch(desc);
+		    int stretch = pango_font_description_get_stretch(desc);
 		    /* Stretch: closer to normal sorts earlier */
-		    n = 2 * abs(PANGO_STRETCH_NORMAL - n) +
-			(n < PANGO_STRETCH_NORMAL);
-		    p += sprintf(p, " %2d", n);
+		    stretch = 2 * abs(PANGO_STRETCH_NORMAL - stretch) +
+			(stretch < PANGO_STRETCH_NORMAL);
+		    strbuf_catf(buf, " %2d", stretch);
 
-		    n = pango_font_description_get_variant(desc);
-		    p += sprintf(p, " %2d", n);
-		    
+		    strbuf_catf(buf, " %2d",
+                                pango_font_description_get_variant(desc));
+
+                    stylekey = strbuf_to_str(buf);
 		}
 
 		/*
@@ -1926,6 +1925,7 @@ static void pangofont_enum_fonts(GtkWidget *widget, fontsel_add_entry callback,
 			 (sizes == &dummysize ? 0 : PANGO_PIXELS(sizes[k])),
 			 flags, &pangofont_vtable);
 
+                sfree(stylekey);
 		g_free(fullname);
 	    }
 	    if (sizes != &dummysize)
diff --git a/unix/uxnet.c b/unix/uxnet.c
index ac3455fa..2c8fd446 100644
--- a/unix/uxnet.c
+++ b/unix/uxnet.c
@@ -195,12 +195,11 @@ SockAddr *sk_namelookup(const char *host, char **canonicalname, int address_fami
     struct hostent *h = NULL;
     int n;
 #endif
-    char realhost[8192];
+    strbuf *realhost;
 
     /* Clear the structure and default to IPv4. */
     memset(ret, 0, sizeof(SockAddr));
     ret->superfamily = UNRESOLVED;
-    *realhost = '\0';
     ret->error = NULL;
     ret->refcount = 1;
 
@@ -225,11 +224,12 @@ SockAddr *sk_namelookup(const char *host, char **canonicalname, int address_fami
 	return ret;
     }
     ret->superfamily = IP;
-    *realhost = '\0';
+
+    realhost = strbuf_new();
     if (ret->ais->ai_canonname != NULL)
-	strncat(realhost, ret->ais->ai_canonname, sizeof(realhost) - 1);
+	strbuf_catf(realhost, "%s", ret->ais->ai_canonname);
     else
-	strncat(realhost, host, sizeof(realhost) - 1);
+	strbuf_catf(realhost, "%s", host);
 #else
     if ((a = inet_addr(host)) == (unsigned long)(in_addr_t)(-1)) {
 	/*
@@ -248,10 +248,12 @@ SockAddr *sk_namelookup(const char *host, char **canonicalname, int address_fami
 			  h_errno == TRY_AGAIN ?
 			  "Temporary name service failure" :
 			  "gethostbyname: unknown error");
+            strbuf_free(realhost);
 	    return ret;
 	}
 	/* This way we are always sure the h->h_name is valid :) */
-	strncpy(realhost, h->h_name, sizeof(realhost));
+        realhost->len = 0;
+	strbuf_catf(realhost, "%s", h->h_name);
 	for (n = 0; h->h_addr_list[n]; n++);
 	ret->addresses = snewn(n, unsigned long);
 	ret->naddresses = n;
@@ -265,15 +267,14 @@ SockAddr *sk_namelookup(const char *host, char **canonicalname, int address_fami
 	 * success return from inet_addr.
 	 */
 	ret->superfamily = IP;
-	strncpy(realhost, host, sizeof(realhost));
+        realhost->len = 0;
+	strbuf_catf(realhost, "%s", host);
 	ret->addresses = snew(unsigned long);
 	ret->naddresses = 1;
 	ret->addresses[0] = ntohl(a);
     }
 #endif
-    realhost[lenof(realhost)-1] = '\0';
-    *canonicalname = snewn(1+strlen(realhost), char);
-    strcpy(*canonicalname, realhost);
+    *canonicalname = strbuf_to_str(realhost);
     return ret;
 }