Boehm garbage collector
In the article we present below, we will delve into the topic of Boehm garbage collector, exploring its different aspects and its relevance today. Boehm garbage collector is a topic that has captured the attention of a wide spectrum of people, from academics and specialists in the field, to individuals interested in understanding its impact on society. Through a detailed and exhaustive analysis, we will seek to unravel its implications and offer a comprehensive vision that allows our readers to better understand this phenomenon. From its origin to its evolution over time, Boehm garbage collector has generated debates and controversies that make it a topic of great interest for different areas of research. Join us on this journey of discovery and reflection about Boehm garbage collector!
| Other names | bdwgc |
|---|---|
| Original author(s) | Hans-Juergen Boehm |
| Developer(s) | Ivan Maidanski, et al. |
| Initial release | 1988 |
| Stable release | 8.2.4
/ May 26, 2023 |
| Repository | |
| Written in | C |
| Type | garbage collector |
| License | similar to X11 (free software) |
| Website | www |
The Boehm–Demers–Weiser garbage collector, often simply known as the Boehm GC or Boehm collector, is a conservative garbage collector for C and C++ developed by Hans Boehm, Alan Demers, and Mark Weiser.
Boehm GC is free software distributed under a permissive free software licence similar to the X11 license. The first paper introducing this collector appeared in 1992.
Design
Hans Boehm describes the operation of the collector as follows:
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, 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.
Boehm GC can also run in leak detection mode in which memory management is still done manually, but the Boehm GC can check if it is done properly. In this way a programmer can find memory leaks and double deallocations.
Boehm GC is also distributed with a C string handling library called cords. This is similar to ropes in C++ (trees of constant small arrays), but instead of using reference counting for proper deallocation, it relies on garbage collection to free objects. Cords are good at handling very large texts, modifications to them in the middle, slicing, concatenating, and keeping history of changes (undo/redo functionality).
Operation
The garbage collector works with most unmodified C programs, simply by replacing malloc() with GC_MALLOC() calls, replacing realloc() with GC_REALLOC() calls, and removing free() calls. The code piece below shows how one can use Boehm instead of traditional malloc and free in C.
#include <assert.h>
#include <stdio.h>
#include <gc.h>
int main(void)
{
int i;
const int size = 10000000;
GC_INIT();
for (i = 0; i < size; ++i)
{
int **p = GC_MALLOC(sizeof *p);
int *q = GC_MALLOC_ATOMIC(sizeof *q);
assert(*p == 0);
*p = GC_REALLOC(q, 2 * sizeof *p);
if (i == size-1)
printf("Heap size = %zu\n", GC_get_heap_size());
}
return 0;
}
For completeness, Boehm supports explicit deallocation via GC_FREE(). All the substitution can be done using preprocessor macros.
Uses and ports
The Boehm GC is used by many projects that are implemented in C or C++ like Inkscape, as well as by runtime environments for a number of other languages, including Crystal, the Codon high performance python compiler, the GNU Compiler for Java runtime environment, the Portable.NET project, Embeddable Common Lisp, GNU Guile, the Mono implementation of the Microsoft .NET platform (also using precise compacting GC since version 2.8), GNUstep optionally, and libgc-d (a binding to libgc for the D programming language, used primarily in the MCI). It supports numerous operating systems, including many Unix variants (such as macOS) and Microsoft Windows, and provides a number of advanced features including incremental collection, parallel collection and a variety of finalizer semantics.
References
- ^ a b Koranne, Sandeep (2011), Handbook of Open Source Tools, Springer, pp. 151–154, Bibcode:2011hoos.book.....K, ISBN 978-1441977199.
- ^ Hans Boehm, A garbage collector for C and C++
- ^ Andrew W. Appel (1998), Modern Compiler Implementation in C - "Boehm Conservative Garbage Collector",
- ^ H. J. Boehm and D. Chase, "A Proposal for Garbage-Collector-Safe C Compilation", The Journal of C Language Translation, Volume 4 Number 2 December 1992, pages 126-141
- ^ Using the Garbage Collector as Leak Detector
- ^ Using the Garbage Collector: A simple example
- ^ "Garbage Collector Interface". www.hboehm.info.
- ^ Known BDWGC uses
- ^ "Exaloop/Codon". GitHub.
- ^ libgc-d
