try hard to free heap memory after command-line termination using malloc_trim()

 * this is a Linux/glibc-only optimization

2 files changed, 18 insertions, 2 deletions

diff --git a/configure.ac b/configure.ac
index 77b71a7..e2f230f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -94,6 +94,11 @@ case $host in
 	;;
 esac
 
+# Check for optional GNU libc features.
+# Will probably only be found on Linux.
+AC_CHECK_HEADERS([malloc.h])
+AC_CHECK_FUNCS([malloc_trim])
+
 #
 # Config options
 #
diff --git a/src/cmdline.cpp b/src/cmdline.cpp
index 83a90b4..599a469 100644
--- a/src/cmdline.cpp
+++ b/src/cmdline.cpp
@@ -19,6 +19,10 @@
 #include "config.h"
 #endif
 
+#ifdef HAVE_MALLOC_H
+#include <malloc.h>
+#endif
+
 #include <string.h>
 #include <signal.h>
 
@@ -446,10 +450,17 @@ Cmdline::process_edit_cmd(gchar key)
 			str = NULL;
 			len = rubout_len = 0;
 
+#ifdef HAVE_MALLOC_TRIM
 			/*
-			 * FIXME: Perhaps to the malloc_trim() here
-			 * instead of in UndoStack::clear()
+			 * Glibc/Linux-only optimization: Undo stacks can grow very
+			 * large - sometimes large enough to make the system
+			 * swap and become unresponsive.
+			 * This will often reduce the amount of memory previously
+			 * freed that's still allocated to the program immediately
+			 * when the command-line is terminated:
 			 */
+			malloc_trim(0);
+#endif
 		} else {
 			insert(key);
 		}