Use malloc_trim when using glibc

* use malloc_trim(0) to return memory to OS after free (after closing window)
* release the memory when clearing history and call malloc_trim()

cmd-clear-history.c

@@ -17,6 +17,9 @@
  */
 
 #include <sys/types.h>
+#ifdef __GLIBC__
+# include <malloc.h>
+#endif
 
 #include "tmux.h"
 
@@ -40,12 +43,24 @@ cmd_clear_history_exec(struct cmd *self, struct cmd_q *cmdq)
 	struct args		*args = self->args;
 	struct window_pane	*wp;
 	struct grid		*gd;
+	struct grid_line    *gl;
+	u_int            yy;
 
 	if (cmd_find_pane(cmdq, args_get(args, 't'), NULL, &wp) == NULL)
 		return (CMD_RETURN_ERROR);
 	gd = wp->base.grid;
 
-	grid_move_lines(gd, 0, gd->hsize, gd->sy);
+	for (yy = 0; yy < gd->hsize+gd->sy; yy++) {
+		gl = &gd->linedata[yy];
+		free(gl->celldata);
+	}
+
+	free(gd->linedata);
+# ifdef M_TRIM_THRESHOLD
+	malloc_trim(0);
+# endif
+
+	gd->linedata = xcalloc(gd->sy, sizeof *gd->linedata);
 	gd->hsize = 0;
 
 	return (CMD_RETURN_NORMAL);

grid.c

@@ -20,6 +20,9 @@
 
 #include <stdlib.h>
 #include <string.h>
+#ifdef __GLIBC__
+# include <malloc.h>
+#endif
 
 #include "tmux.h"
 
@@ -113,6 +116,10 @@ grid_destroy(struct grid *gd)
 	free(gd->linedata);
 
 	free(gd);
+
+# ifdef M_TRIM_THRESHOLD
+       malloc_trim(0);
+# endif
 }
 
 /* Compare grids. */