| |
| =========================================================================== |
| Michel Schinz's notes |
| =========================================================================== |
| WHO DID WHAT |
| |
| The original Amiga port was made by Jesper Peterson. I (Michel Schinz) |
| modified it slightly to reflect the changes made in the new official |
| distributions, and to take advantage of the new SAS/C 6.x features. I also |
| created a makefile to compile the "cord" package (see the cord |
| subdirectory). |
| |
| TECHNICAL NOTES |
| |
| In addition to Jesper's notes, I have the following to say: |
| |
| - Starting with version 4.3, gctest checks to see if the code segment is |
| added to the root set or not, and complains if it is. Previous versions |
| of this Amiga port added the code segment to the root set, so I tried to |
| fix that. The only problem is that, as far as I know, it is impossible to |
| know which segments are code segments and which are data segments (there |
| are indeed solutions to this problem, like scanning the program on disk |
| or patch the LoadSeg functions, but they are rather complicated). The |
| solution I have chosen (see os_dep.c) is to test whether the program |
| counter is in the segment we are about to add to the root set, and if it |
| is, to skip the segment. The problems are that this solution is rather |
| awkward and that it works only for one code segment. This means that if |
| your program has more than one code segment, all of them but one will be |
| added to the root set. This isn't a big problem in fact, since the |
| collector will continue to work correctly, but it may be slower. |
| |
| Anyway, the code which decides whether to skip a segment or not can be |
| removed simply by not defining AMIGA_SKIP_SEG. But notice that if you do |
| so, gctest will complain (it will say that "GC_is_visible produced wrong |
| failure indication"). However, it may be useful if you happen to have |
| pointers stored in a code segment (you really shouldn't). |
| |
| If anyone has a good solution to the problem of finding, when a program |
| is loaded in memory, whether a segment is a code or a data segment, |
| please let me know. |
| |
| PROBLEMS |
| |
| If you have any problem with this version, please contact me at |
| schinz@alphanet.ch (but do *not* send long files, since we pay for |
| every mail!). |
| |
| =========================================================================== |
| Jesper Peterson's notes |
| =========================================================================== |
| |
| ADDITIONAL NOTES FOR AMIGA PORT |
| |
| These notes assume some familiarity with Amiga internals. |
| |
| WHY I PORTED TO THE AMIGA |
| |
| The sole reason why I made this port was as a first step in getting |
| the Sather(*) language on the Amiga. A port of this language will |
| be done as soon as the Sather 1.0 sources are made available to me. |
| Given this motivation, the garbage collection (GC) port is rather |
| minimal. |
| |
| (*) For information on Sather read the comp.lang.sather newsgroup. |
| |
| LIMITATIONS |
| |
| This port assumes that the startup code linked with target programs |
| is that supplied with SAS/C versions 6.0 or later. This allows |
| assumptions to be made about where to find the stack base pointer |
| and data segments when programs are run from WorkBench, as opposed |
| to running from the CLI. The compiler dependent code is all in the |
| GC_get_stack_base() and GC_register_data_segments() functions, but |
| may spread as I add Amiga specific features. |
| |
| Given that SAS/C was assumed, the port is set up to be built with |
| "smake" using the "SMakefile". Compiler options in "SCoptions" can |
| be set with "scopts" program. Both "smake" and "scopts" are part of |
| the SAS/C commercial development system. |
| |
| In keeping with the porting philosophy outlined above, this port |
| will not behave well with Amiga specific code. Especially not inter- |
| process comms via messages, and setting up public structures like |
| Intuition objects or anything else in the system lists. For the |
| time being the use of this library is limited to single threaded |
| ANSI/POSIX compliant or near-complient code. (ie. Stick to stdio |
| for now). Given this limitation there is currently no mechanism for |
| allocating "CHIP" or "PUBLIC" memory under the garbage collector. |
| I'll add this after giving it considerable thought. The major |
| problem is the entire physical address space may have to me scanned, |
| since there is no telling who we may have passed memory to. |
| |
| If you allocate your own stack in client code, you will have to |
| assign the pointer plus stack size to GC_stackbottom. |
| |
| The initial stack size of the target program can be compiled in by |
| setting the __stack symbol (see SAS documentaion). It can be over- |
| ridden from the CLI by running the AmigaDOS "stack" program, or from |
| the WorkBench by setting the stack size in the tool types window. |
| |
| SAS/C COMPILER OPTIONS (SCoptions) |
| |
| You may wish to check the "CPU" code option is appropriate for your |
| intended target system. |
| |
| Under no circumstances set the "StackExtend" code option in either |
| compiling the library or *ANY* client code. |
| |
| All benign compiler warnings have been suppressed. These mainly |
| involve lack of prototypes in the code, and dead assignments |
| detected by the optimizer. |
| |
| THE GOOD NEWS |
| |
| The library as it stands is compatible with the GigaMem commercial |
| virtual memory software, and probably similar PD software. |
| |
| The performance of "gctest" on an Amiga 2630 (68030 @ 25Mhz) |
| compares favourably with an HP9000 with similar architecture (a 325 |
| with a 68030 I think). |
| |
| ----------------------------------------------------------------------- |
| |
| The Amiga port has been brought to you by: |
| |
| Jesper Peterson. |
| |
| jep@mtiame.mtia.oz.au (preferred, but 1 week turnaround) |
| jep@orca1.vic.design.telecom.au (that's orca<one>, 1 day turnaround) |
| |
| At least one of these addresses should be around for a while, even |
| though I don't work for either of the companies involved. |
| |