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===========================================================================
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Kjetil S. Matheussen's notes (28-11-2000)
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===========================================================================
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Compiles under SAS/C again. Should allso still compile under other
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amiga compilers without big changes. I haven't checked if it still
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works under gcc, because I don't have gcc for amiga. But I have
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updated 'Makefile', and hope it compiles fine.
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Made a pretty big effort in preventing GCs allocating-functions from returning
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The lower part of the new file AmigaOS.c does this in various ways, mainly by
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wrapping GC_malloc, GC_malloc_atomic, GC_malloc_uncollectable,
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GC_malloc_atomic_uncollectable, GC_malloc_stubborn, GC_malloc_ignore_off_page
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and GC_malloc_atomic_ignore_off_page. GC_realloc is allso wrapped, but
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doesn't do the same effort in preventing to return chip-mem.
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Other allocating-functions (f.ex. GC_*_typed_) can probably be
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used without any problems, but beware that the warn hook will not be called.
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In case of problems, don't define GC_AMIGA_FASTALLOC.
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Programs using more time actually using the memory allocated
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(instead of just allocate and free rapidly) have
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the most to earn on this, but even gctest now normally runs twice
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as fast and uses less memory, on my poor 8MB machine.
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The changes have only effect when there is no more
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fast-mem left. But with the way GC works, it
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could happen quite often. Beware that an atexit handler had to be added,
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so using the abort() function will make a big memory-loss.
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If you absolutely must call abort() instead of exit(), try calling
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the GC_amiga_free_all_mem function before abort().
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New amiga-spesific compilation flags:
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GC_AMIGA_FASTALLOC - By NOT defining this option, GC will work like before,
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it will not try to force fast-mem out of the OS, and
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it will use normal calloc for allocation, and the rest
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of the following flags will have no effect.
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GC_AMIGA_ONLYFAST - Makes GC never to return chip-mem. GC_AMIGA_RETRY have
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no effect if this flag is set.
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GC_AMIGA_GC - If gc returns NULL, do a GC_gcollect, and try again. This
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usually is a success with the standard GC configuration.
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It is allso the most important flag to set to prevent
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GC from returning chip-mem. Beware that it slows down a lot
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when a program is rapidly allocating/deallocating when
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theres either very little fast-memory left or verly little
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chip-memory left. Its not a very common situation, but gctest
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sometimes (very rare) use many minutes because of this.
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GC_AMIGA_RETRY - If gc succeed allocating memory, but it is chip-mem,
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try again and see if it is fast-mem. Most of the time,
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it will actually return fast-mem for the second try.
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I have set max number of retries to 9 or size/5000. You
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can change this if you like. (see GC_amiga_rec_alloc())
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GC_AMIGA_PRINTSTATS - Gather some statistics during the execution of a
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program, and prints out the info when the atexit-handler
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My reccomendation is to set all this flags, except GC_AMIGA_PRINTSTATS and
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If your program demands high response-time, you should
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not define GC_AMIGA_GC, and possible allso define GC_AMIGA_ONLYFAST.
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GC_AMIGA_RETRY does not seem to slow down much.
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Allso, when compiling up programs, and GC_AMIGA_FASTALLOC was not defined when
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compilling gc, you can define GC_AMIGA_MAKINGLIB to avoid having these allocation-
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functions wrapped. (see gc.h)
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Note that GC_realloc must not be called before any of
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the other above mentioned allocating-functions have been called. (shouldn't be
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any programs doing so either, I hope).
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Another note. The allocation-function is wrapped when defining
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GC_AMIGA_FASTALLOC by letting the function go thru the new
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GC_amiga_allocwrapper_do function-pointer (see gc.h). Means that
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sending function-pointers, such as GC_malloc, GC_malloc_atomic, etc.,
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for later to be called like f.ex this, (*GC_malloc_functionpointer)(size),
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will not wrap the function. This is normally not a big problem, unless
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all allocation function is called like this, which will cause the
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atexit un-allocating function never to be called. Then you either
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have to manually add the atexit handler, or call the allocation-
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functions function-pointer functions like this;
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(*GC_amiga_allocwrapper_do)(size,GC_malloc_functionpointer).
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There are probably better ways this problem could be handled, unfortunately,
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I didn't find any without rewriting or replacing a lot of the GC-code, which
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I really didn't want to. (Making new GC_malloc_* functions, and just
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define f.ex GC_malloc as GC_amiga_malloc should allso work).
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New amiga-spesific function:
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void GC_amiga_set_toany(void (*func)(void));
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'func' is a function that will be called right before gc has to change
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allocation-method from MEMF_FAST to MEMF_ANY. Ie. when it is likely
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it will return chip-mem.
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2. A few small compiler-spesific additions to make it compile with SAS/C again.
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3. Updated and rewritten the smakefile, so that it works again and that
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the "unnecesarry" 'SCOPTIONS' files could be removed. Allso included
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the cord-smakefile stuff in the main smakefile, so that the cord smakefile
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could be removed too. By writing smake -f Smakefile.smk, both gc.lib and
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cord.lib will be made.
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Programs can not be started from workbench, at least not for SAS/C. (Martin
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Tauchmanns note about that it now works with workbench is definitely wrong
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when concerning SAS/C). I guess it works if you use the old "#if 0'ed"-code,
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but I haven't tested it. I think the reason for MT to replace the
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"#if 0'ed"-code was only because it was a bit to SAS/C-spesific. But I
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don't know. An iconx-script solves this problem anyway.
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-To run gctest, set the stack to around 200000 bytes first.
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-SAS/C-spesific: cord will crash if you compile gc.lib with
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either parm=reg or parm=both. (missing legal prototypes for
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function-pointers someplace is the reason I guess.).
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tested with software: Radium, http://www.stud.ifi.uio.no/~ksvalast/radium/
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tested with hardware: MC68060
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===========================================================================
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Martin Tauchmann's notes (1-Apr-99)
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===========================================================================
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Works now, also with the GNU-C compiler V2.7.2.1. <ftp://ftp.unina.it/pub/amiga/geekgadgets/amiga/m68k/snapshots/971125/amiga-bin/>
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Modify the `Makefile`
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- `GC_get_stack_base()`, `GC_register_data_segments()` works now with every
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C compiler; also Workbench.
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- Removed AMIGA_SKIP_SEG, but the Code-Segment must not be scanned by GC.
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- When the Linker, does`t merge all Code-Segments to an single one. LD of GCC
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- With ixemul.library V47.3, when an GC program launched from another program
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(example: `Make` or `if_mach M68K AMIGA gctest`), `GC_register_data_segments()`
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found the Segment-List of the caller program.
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Can be fixed, if the run-time initialization code (for C programs, usually *crt0*)
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support `__data` and `__bss`.
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- PowerPC Amiga currently not supported.
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- Dynamic libraries (dyn_load.c) not supported.
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`Optimized Oberon 2 C` (oo2c) <http://cognac.informatik.uni-kl.de/download/index.html>
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Please, contact me at <martintauchmann@bigfoot.com>, when you change the
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Amiga port. <http://martintauchmann.home.pages.de>
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===========================================================================
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Michel Schinz's notes
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===========================================================================
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The original Amiga port was made by Jesper Peterson. I (Michel Schinz)
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modified it slightly to reflect the changes made in the new official
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distributions, and to take advantage of the new SAS/C 6.x features. I also
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created a makefile to compile the "cord" package (see the cord
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In addition to Jesper's notes, I have the following to say:
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- Starting with version 4.3, gctest checks to see if the code segment is
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added to the root set or not, and complains if it is. Previous versions
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of this Amiga port added the code segment to the root set, so I tried to
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fix that. The only problem is that, as far as I know, it is impossible to
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know which segments are code segments and which are data segments (there
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are indeed solutions to this problem, like scanning the program on disk
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or patch the LoadSeg functions, but they are rather complicated). The
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solution I have chosen (see os_dep.c) is to test whether the program
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counter is in the segment we are about to add to the root set, and if it
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is, to skip the segment. The problems are that this solution is rather
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awkward and that it works only for one code segment. This means that if
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your program has more than one code segment, all of them but one will be
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added to the root set. This isn't a big problem in fact, since the
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collector will continue to work correctly, but it may be slower.
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Anyway, the code which decides whether to skip a segment or not can be
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removed simply by not defining AMIGA_SKIP_SEG. But notice that if you do
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so, gctest will complain (it will say that "GC_is_visible produced wrong
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failure indication"). However, it may be useful if you happen to have
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pointers stored in a code segment (you really shouldn't).
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If anyone has a good solution to the problem of finding, when a program
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is loaded in memory, whether a segment is a code or a data segment,
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If you have any problem with this version, please contact me at
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schinz@alphanet.ch (but do *not* send long files, since we pay for
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===========================================================================
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Jesper Peterson's notes
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===========================================================================
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ADDITIONAL NOTES FOR AMIGA PORT
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These notes assume some familiarity with Amiga internals.
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WHY I PORTED TO THE AMIGA
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The sole reason why I made this port was as a first step in getting
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the Sather(*) language on the Amiga. A port of this language will
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be done as soon as the Sather 1.0 sources are made available to me.
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Given this motivation, the garbage collection (GC) port is rather
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(*) For information on Sather read the comp.lang.sather newsgroup.
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This port assumes that the startup code linked with target programs
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is that supplied with SAS/C versions 6.0 or later. This allows
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assumptions to be made about where to find the stack base pointer
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and data segments when programs are run from WorkBench, as opposed
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to running from the CLI. The compiler dependent code is all in the
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GC_get_stack_base() and GC_register_data_segments() functions, but
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may spread as I add Amiga specific features.
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Given that SAS/C was assumed, the port is set up to be built with
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"smake" using the "SMakefile". Compiler options in "SCoptions" can
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be set with "scopts" program. Both "smake" and "scopts" are part of
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the SAS/C commercial development system.
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In keeping with the porting philosophy outlined above, this port
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will not behave well with Amiga specific code. Especially not inter-
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process comms via messages, and setting up public structures like
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Intuition objects or anything else in the system lists. For the
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time being the use of this library is limited to single threaded
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ANSI/POSIX compliant or near-complient code. (ie. Stick to stdio
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for now). Given this limitation there is currently no mechanism for
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allocating "CHIP" or "PUBLIC" memory under the garbage collector.
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I'll add this after giving it considerable thought. The major
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problem is the entire physical address space may have to me scanned,
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since there is no telling who we may have passed memory to.
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If you allocate your own stack in client code, you will have to
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assign the pointer plus stack size to GC_stackbottom.
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The initial stack size of the target program can be compiled in by
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setting the __stack symbol (see SAS documentaion). It can be over-
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ridden from the CLI by running the AmigaDOS "stack" program, or from
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the WorkBench by setting the stack size in the tool types window.
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SAS/C COMPILER OPTIONS (SCoptions)
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You may wish to check the "CPU" code option is appropriate for your
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intended target system.
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Under no circumstances set the "StackExtend" code option in either
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compiling the library or *ANY* client code.
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All benign compiler warnings have been suppressed. These mainly
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involve lack of prototypes in the code, and dead assignments
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detected by the optimizer.
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The library as it stands is compatible with the GigaMem commercial
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virtual memory software, and probably similar PD software.
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The performance of "gctest" on an Amiga 2630 (68030 @ 25Mhz)
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compares favourably with an HP9000 with similar architecture (a 325
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with a 68030 I think).
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-----------------------------------------------------------------------
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The Amiga port has been brought to you by:
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jep@mtiame.mtia.oz.au (preferred, but 1 week turnaround)
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jep@orca1.vic.design.telecom.au (that's orca<one>, 1 day turnaround)
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At least one of these addresses should be around for a while, even
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though I don't work for either of the companies involved.
added
removed
jam_src/boehm_gc/doc/README.amiga
