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Self-collecting mutators for the C programming language

  • Copyright (c) 2010, the Short-term Memory Project Authors.
  • All rights reserved. Please see the AUTHORS file for details.
  • Use of this source code is governed by a BSD license that
  • can be found in the LICENSE file.

Self-collecting mutators implement the short-term memory model described in:

@InProceedings{ISMM11, author = {M. Aigner and A. Haas and C.M. Kirsch and M. Lippautz and A. Sokolova and S. Stroka and A. Unterweger}, title = {Short-term Memory for Self-collecting Mutators}, booktitle = {Proc. International Symposium on Memory Management (ISMM)}, year = {2011}, publisher = {ACM} }


We propose a new memory model for heap management, called short-term memory, and concurrent implementations of short-term memory for Java and C, called self-collecting mutators. In short-term memory objects on the heap expire after a finite amount of time, which makes deallocation unnecessary. Self-collecting mutators require programmer support to control the progress of time and thereby enable reclaiming the memory of expired objects. We identify a class of programs for which programmer support is easy and correctness is guaranteed. Self-collecting mutators perform competitively with garbage-collected and explicitly managed systems, as shown by our experimental results on several benchmarks. Unlike garbage-collected systems, self-collecting mutators do not introduce pause times and provide constant execution time of all operations, independent of the number of live objects, and constant (short-term) memory consumption after a steady state has been reached. Self-collecting mutators can be linked against any unmodified C code introducing a one-word overhead per heap object and negligible runtime overhead. Short-term memory may then be used to remove explicit deallocation of some but not necessarily all objects.

Additional Features

The latest version also supports regions and multiple clocks.

How to build libscm

  • Use a recent version of gcc. libscm is known to work with gcc 4.4.3 on Linux x86.
  • Run make to build the shared library.
  • The library ( and the public header files reside in the dist subdirectory.
  • Take a look at the examples subdirectory (C files and Makefile) to find out how to build a program using libscm, see also the script.
  • There is also a port of sh6bench for benchmarking libscm in bench/sh6bench, see the script.

Building Build Status

Additional Information

Take a look at our project webpage:

Detailed information regarding the implementation can be found here: