tweaks: avoid a few needless reallocations

Most of these variables are freed moments later -- reallocating
them is thus a waste of time.

src/browser.c

@@ -587,7 +587,7 @@ void browser_refresh(void)
 	/* Make sure info takes up no more than infomaxlen columns. */
 	infolen = strlenpt(info);
 	if (infolen > infomaxlen) {
-	    null_at(&info, actual_x(info, infomaxlen));
+	    info[actual_x(info, infomaxlen)] = '\0';
 	    infolen = infomaxlen;
 	}
 

src/files.c

@@ -1028,9 +1028,8 @@ char *get_next_filename(const char *name, const char *suffix)
 	sprintf(buf + wholenamelen, ".%lu", i);
     }
 
-    /* We get here only if there is no possible save file.  Blank out
-     * the filename to indicate this. */
-    null_at(&buf, 0);
+    /* There is no possible save file: blank out the filename. */
+    *buf = '\0';
 
     return buf;
 }
@@ -1228,7 +1227,7 @@ char *get_full_path(const char *origpath)
 	/* How often we've tried climbing back up the tree. */
     struct stat fileinfo;
     char *currentdir, *d_here, *d_there, *d_there_file = NULL;
-    const char *last_slash;
+    char *last_slash;
     bool path_only;
 
     if (origpath == NULL)
@@ -1294,7 +1293,7 @@ char *get_full_path(const char *origpath)
 	    d_there_file = mallocstrcpy(NULL, last_slash + 1);
 
 	/* Remove the filename portion of the answer from d_there. */
-	null_at(&d_there, last_slash - d_there + 1);
+	*(last_slash + 1) = '\0';
 
 	/* Go to the path specified in d_there. */
 	if (chdir(d_there) == -1) {
@@ -2503,7 +2502,7 @@ char **cwd_tab_completion(const char *buf, bool allow_files, size_t
     const struct dirent *nextdir;
 
     *num_matches = 0;
-    null_at(&dirname, buf_len);
+    dirname[buf_len] = '\0';
 
     /* If there's a / in the name, split out filename and directory parts. */
     slash = strrchr(dirname, '/');

src/nano.c

@@ -228,7 +228,7 @@ partition *partition_filestruct(filestruct *top, size_t top_x,
     p->bot_data = mallocstrcpy(NULL, bot->data + bot_x);
 
     /* Remove all text after bot_x at the bottom of the partition. */
-    null_at(&bot->data, bot_x);
+    bot->data[bot_x] = '\0';
 
     /* Remove all text before top_x at the top of the partition. */
     charmove(top->data, top->data + top_x, strlen(top->data) - top_x + 1);

src/prompt.c

@@ -296,7 +296,7 @@ void do_statusbar_cut_text(void)
     if (!ISSET(CUT_TO_END))
 	statusbar_x = 0;
 
-    null_at(&answer, statusbar_x);
+    answer[statusbar_x] = '\0';
 
     update_the_statusbar();
 }
@@ -637,7 +637,7 @@ int do_prompt(bool allow_tabs, bool allow_files,
     vsnprintf(prompt, COLS * mb_cur_max(), msg, ap);
     va_end(ap);
     /* Reserve five columns for colon plus angles plus answer, ":<aa>". */
-    null_at(&prompt, actual_x(prompt, (COLS < 5) ? 0 : COLS - 5));
+    prompt[actual_x(prompt, (COLS < 5) ? 0 : COLS - 5)] = '\0';
 
     func = acquire_an_answer(&retval, allow_tabs, allow_files, &listed,
 #ifndef DISABLE_HISTORIES

src/search.c

@@ -1046,7 +1046,7 @@ void do_find_bracket(void)
     bracket_set = charalloc((mb_cur_max() * 2) + 1);
     strncpy(bracket_set, ch, ch_len);
     strncpy(bracket_set + ch_len, wanted_ch, wanted_ch_len);
-    null_at(&bracket_set, ch_len + wanted_ch_len);
+    bracket_set[ch_len + wanted_ch_len] = '\0';
 
     found_ch = charalloc(mb_cur_max() + 1);
 

src/text.c

@@ -1226,7 +1226,7 @@ void add_undo(undo_type action)
 	    char *char_buf = charalloc(mb_cur_max() + 1);
 	    int char_len = parse_mbchar(&openfile->current->data[u->begin],
 						char_buf, NULL);
-	    null_at(&char_buf, char_len);
+	    char_buf[char_len] = '\0';
 	    u->strdata = char_buf;
 	    if (u->type == BACK)
 		u->mark_begin_x += char_len;