Boehm-Demers-Weiser Conservative Garbage Collector 6.8 review

The Boehm-Demers-Weiser conservative garbage collector can be used as a garbage collecting replacement for C malloc or C++ new. Bo

License: BSD License File size: 739K Developer: Hans-J. Boehm

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The Boehm-Demers-Weiser conservative garbage collector can be used as a garbage collecting replacement for C malloc or C++ new.

Boehm-Demers-Weiser Conservative Garbage Collector allows you to allocate memory basically as you normally would, without explicitly deallocating memory that is no longer useful. The collector automatically recycles memory when it determines that it can no longer be otherwise accessed.

The collector is also used by a number of programming language implementations that either use C as intermediate code, want to facilitate easier interoperation with C libraries, or just prefer the simple collector interface.

Alternatively, the garbage collector may be used as a leak detector for C or C++ programs, though that is not its primary goal.

Typically several versions will be available. Usually you should first try to use gc_source/gc.tar.gz, which is normally an older, more stable version.

If that fails, try the latest explicitly numbered version in gc_source/. Later versions may contain additional features, platform support, or bug fixes, but are likely to be less well tested. Note that versions containing the letters alpha are even less well tested than others, especially on non-HP platforms.

A slightly older version of the garbage collector is now also included as part of the GNU compiler distribution.

The collector uses a mark-sweep algorithm. It provides incremental and generational collection under operating systems which provide the right kind of virtual memory support. (Currently this includes SunOS[45], IRIX, OSF/1, Linux, and Windows, with varying restrictions.)

It allows finalization code to be invoked when an object is collected. It can take advantage of type information to locate pointers if such information is provided, but it is usually used without such information. ee the README and gc.h files in the distribution for more details.

The garbage collector distribution includes a C string (cord) package that provides for fast concatenation and substring operations on long strings. A simple curses- and win32-based editor that represents the entire file as a cord is included as a sample application.

Performance of the nonincremental collector is typically competitive with malloc/free implementations. Both space and time overhead are likely to be only slightly higher for programs written for malloc/free (see Detlefs, Dosser and Zorn's Memory Allocation Costs in Large C and C++ Programs.)

For programs allocating primarily very small objects, the collector may be faster; for programs allocating primarily large objects it will be slower. If the collector is used in a multithreaded environment and configured for thread-local allocation, it may in some cases significantly outperform malloc/free allocation in time.

We also expect that in many cases any additional overhead will be more than compensated for by decreased copying etc. if programs are written and tuned for garbage collection.

What's New in This Release:
Support for Solaris/x86-64, for Dragonfly BSD, and for kFreeBSD+glibc was added.
Mac OS thread memory leaks, a MinGW malloc redirection bug, and several other minor bugs were fixed.