Annotation of OpenXM_contrib2/asir2000/gc5.3/README.amiga, Revision 1.1.1.1
1.1 noro 1: ===========================================================================
2: Martin Tauchmann's notes (1-Apr-99)
3: ===========================================================================
4:
5: 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/>
6: Modify the `Makefile`
7: CC=cc $(ABI_FLAG)
8: to
9: CC=gcc $(ABI_FLAG)
10:
11: TECHNICAL NOTES
12:
13: - `GC_get_stack_base()`, `GC_register_data_segments()` works now with every
14: C compiler; also Workbench.
15:
16: - Removed AMIGA_SKIP_SEG, but the Code-Segment must not be scanned by GC.
17:
18:
19: PROBLEMS
20: - When the Linker, does`t merge all Code-Segments to an single one. LD of GCC
21: do it always.
22:
23: - With ixemul.library V47.3, when an GC program launched from another program
24: (example: `Make` or `if_mach M68K AMIGA gctest`), `GC_register_data_segments()`
25: found the Segment-List of the caller program.
26: Can be fixed, if the run-time initialization code (for C programs, usually *crt0*)
27: support `__data` and `__bss`.
28:
29: - PowerPC Amiga currently not supported.
30:
31: - Dynamic libraries (dyn_load.c) not supported.
32:
33:
34: TESTED WITH SOFTWARE
35:
36: `Optimized Oberon 2 C` (oo2c) <http://cognac.informatik.uni-kl.de/download/index.html>
37:
38:
39: TESTED WITH HARDWARE
40:
41: MC68030
42:
43:
44: CONTACT
45:
46: Please, contact me at <martintauchmann@bigfoot.com>, when you change the
47: Amiga port. <http://martintauchmann.home.pages.de>
48:
49: ===========================================================================
50: Michel Schinz's notes
51: ===========================================================================
52: WHO DID WHAT
53:
54: The original Amiga port was made by Jesper Peterson. I (Michel Schinz)
55: modified it slightly to reflect the changes made in the new official
56: distributions, and to take advantage of the new SAS/C 6.x features. I also
57: created a makefile to compile the "cord" package (see the cord
58: subdirectory).
59:
60: TECHNICAL NOTES
61:
62: In addition to Jesper's notes, I have the following to say:
63:
64: - Starting with version 4.3, gctest checks to see if the code segment is
65: added to the root set or not, and complains if it is. Previous versions
66: of this Amiga port added the code segment to the root set, so I tried to
67: fix that. The only problem is that, as far as I know, it is impossible to
68: know which segments are code segments and which are data segments (there
69: are indeed solutions to this problem, like scanning the program on disk
70: or patch the LoadSeg functions, but they are rather complicated). The
71: solution I have chosen (see os_dep.c) is to test whether the program
72: counter is in the segment we are about to add to the root set, and if it
73: is, to skip the segment. The problems are that this solution is rather
74: awkward and that it works only for one code segment. This means that if
75: your program has more than one code segment, all of them but one will be
76: added to the root set. This isn't a big problem in fact, since the
77: collector will continue to work correctly, but it may be slower.
78:
79: Anyway, the code which decides whether to skip a segment or not can be
80: removed simply by not defining AMIGA_SKIP_SEG. But notice that if you do
81: so, gctest will complain (it will say that "GC_is_visible produced wrong
82: failure indication"). However, it may be useful if you happen to have
83: pointers stored in a code segment (you really shouldn't).
84:
85: If anyone has a good solution to the problem of finding, when a program
86: is loaded in memory, whether a segment is a code or a data segment,
87: please let me know.
88:
89: PROBLEMS
90:
91: If you have any problem with this version, please contact me at
92: schinz@alphanet.ch (but do *not* send long files, since we pay for
93: every mail!).
94:
95: ===========================================================================
96: Jesper Peterson's notes
97: ===========================================================================
98:
99: ADDITIONAL NOTES FOR AMIGA PORT
100:
101: These notes assume some familiarity with Amiga internals.
102:
103: WHY I PORTED TO THE AMIGA
104:
105: The sole reason why I made this port was as a first step in getting
106: the Sather(*) language on the Amiga. A port of this language will
107: be done as soon as the Sather 1.0 sources are made available to me.
108: Given this motivation, the garbage collection (GC) port is rather
109: minimal.
110:
111: (*) For information on Sather read the comp.lang.sather newsgroup.
112:
113: LIMITATIONS
114:
115: This port assumes that the startup code linked with target programs
116: is that supplied with SAS/C versions 6.0 or later. This allows
117: assumptions to be made about where to find the stack base pointer
118: and data segments when programs are run from WorkBench, as opposed
119: to running from the CLI. The compiler dependent code is all in the
120: GC_get_stack_base() and GC_register_data_segments() functions, but
121: may spread as I add Amiga specific features.
122:
123: Given that SAS/C was assumed, the port is set up to be built with
124: "smake" using the "SMakefile". Compiler options in "SCoptions" can
125: be set with "scopts" program. Both "smake" and "scopts" are part of
126: the SAS/C commercial development system.
127:
128: In keeping with the porting philosophy outlined above, this port
129: will not behave well with Amiga specific code. Especially not inter-
130: process comms via messages, and setting up public structures like
131: Intuition objects or anything else in the system lists. For the
132: time being the use of this library is limited to single threaded
133: ANSI/POSIX compliant or near-complient code. (ie. Stick to stdio
134: for now). Given this limitation there is currently no mechanism for
135: allocating "CHIP" or "PUBLIC" memory under the garbage collector.
136: I'll add this after giving it considerable thought. The major
137: problem is the entire physical address space may have to me scanned,
138: since there is no telling who we may have passed memory to.
139:
140: If you allocate your own stack in client code, you will have to
141: assign the pointer plus stack size to GC_stackbottom.
142:
143: The initial stack size of the target program can be compiled in by
144: setting the __stack symbol (see SAS documentaion). It can be over-
145: ridden from the CLI by running the AmigaDOS "stack" program, or from
146: the WorkBench by setting the stack size in the tool types window.
147:
148: SAS/C COMPILER OPTIONS (SCoptions)
149:
150: You may wish to check the "CPU" code option is appropriate for your
151: intended target system.
152:
153: Under no circumstances set the "StackExtend" code option in either
154: compiling the library or *ANY* client code.
155:
156: All benign compiler warnings have been suppressed. These mainly
157: involve lack of prototypes in the code, and dead assignments
158: detected by the optimizer.
159:
160: THE GOOD NEWS
161:
162: The library as it stands is compatible with the GigaMem commercial
163: virtual memory software, and probably similar PD software.
164:
165: The performance of "gctest" on an Amiga 2630 (68030 @ 25Mhz)
166: compares favourably with an HP9000 with similar architecture (a 325
167: with a 68030 I think).
168:
169: -----------------------------------------------------------------------
170:
171: The Amiga port has been brought to you by:
172:
173: Jesper Peterson.
174:
175: jep@mtiame.mtia.oz.au (preferred, but 1 week turnaround)
176: jep@orca1.vic.design.telecom.au (that's orca<one>, 1 day turnaround)
177:
178: At least one of these addresses should be around for a while, even
179: though I don't work for either of the companies involved.
180:
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