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BCPL/History
This website contains an archive of files for the Acorn Electron, BBC Micro, Acorn Archimedes, Commodore 16 and Commodore 64 computers, which Dominic Ford has rescued from his private collection of floppy disks and cassettes.
Some of these files were originally commercial releases in the 1980s and 1990s, but they are now widely available online. I assume that copyright over them is no longer being asserted. If you own the copyright and would like files to be removed, please contact me.
| Tape/disk: | Home » Archimedes archive » Zipped Apps » BCPL |
| Filename: | BCPL/History |
| Read OK: | ✔ |
| File size: | 14D6 bytes |
| Load address: | 0000 |
| Exec address: | 0000 |
File contents
Note: the phrase 'Found in CG n.m' should not be taken to imply that the
problem concerned does not exist in earlier versions of the compiler.
Bug 1: Found in CG 2.10 Fixed in CG 2.11
In some circumstances, a construct of the form a := b; b := c can be
effectively compiled in the wrong order, so that afterwards a = b = c.
New feature in CG 2.11
There is now some degree of checking for integer operands used with floating
point operators, and vice versa. This cannot be complete, but at any rate
if you write x#+1 you will get a warning. The code compiled for such an
expression is the same as before (no coercion is done).
Bug 2: Found in CG 2.11 Fixed in CG 2.12
A procedure which ends by calling another with five arguments, and which
otherwise contains no procedure call (and which is sufficiently small) may
wrongly be compiled as needing no stackframe, meaning that the value of
argument 5 in the called procedure will be wrong.
Bug 3: Found in CG 2.12 Fixed in CG 2.13
An expression of the form (p+k)!(n*q), where k is a constant and n is even
may be compiled as if it were p!(n*q) (if there was a previous p!... so
that a shifted version of p is still present in a register).
Feature: in CG 2.12 and all earlier Fixed in CG 2.13
The code generated for floating-point operations uses the first version of the
floating-point instruction set. Floating point is thus not available under
Arthur, for which only an emulator for the second version of the instruction
set is available.
Feature: in CG 2.12 and all earlier
When handling GET "filename", the compiler looks first for a file named
filename, and then for :0.alib.filename (and it is an error if neither exists).
This isn't too appropriate for Arthur now, where :0 is the floppy. I believe
that the search path should be user-suppliable, and that the default path
should have $.alib in place of :0.alib. Currently, the path is fixed but it
is possible to specify where particular header files live by something like
-HDR "LibHdr=a.b.c.LibHdr"
on the command line.
Bug 4: Found in CG 2.12 Fixed in CG 2.13
Where a sufficiently simple procedure (containing no calls is a necessary but
not sufficient constraint) returns as result the value of a static variable,
it may not load the pointer to the static variable area first, so that the
procedure acts correctly if called from within the same compilation unit, but
not if called externally.
Bug 5: Found in CG 2.13 (also exists in all earlier versions)
Fixed in CG 2.14
VCAR (x+k) := floating point value gets the offset k 4 times too large (not
shifting it down, since the instructions shift it up).
Bug 6: Found in CG 2.13 Fixed in CG 2.14
FIX always reads from FP reg 0, not the one the operand happens to be in.
(At places like just after procedure calls, this will in fact be right).
Bug 7: Found in CG 2.13 Fixed in CG 2.14
The fix to cure bug 4 above is wrong for procedures near the end of a compiled
section (starting within the last 512 words). And whereas in the previous
state all that happened was that the wrong value was returned, now there may be
a data abort or address exception.
New feature in front end 2.2
It is now possible to switch off the special (for Cambridge Lisp) reserved
words NIL, LGE, LLE, LGT and LGR. The L option controls their admissibility;
it is on by default (switched off by ... -opt -l).
Bug 8: Found in CG 2.13 Fixed in CG 2.14
The result of a/2, where a is negative, is (-a)/2.
Bug 9: Found in CG 2.14 Fixed in CG 2.14
Where a section has a very large number of (any combination of) STATIC
variables, TABLE elements and numeric constants too large to fit into a DP
instruction, the compiler may generate an internal error of the form:
Resolve reference: offset ... at ....
Bug 10: Found in CG 2.14 Fixed in CG 2.15
Further to 9, if a procedure is large and contains no use of STATIC variables,
TABLEs or strings, but does use large constants, the same internal error may
occur.
Bug 11: Found in CG 2.14 Fixed in CG 2.15
The following sort of construct
LET x = ...;
LET y = ...;
IF ...<#x1234 THEN {
LET z = ...;
LET zz = ...;
may (in circumstances easy to explain only in terms of the generated code)
cause the values for z and zz to be written to completely the wrong place in
store. The important thing here is a comparison against a constant breakable
into two 8 bit chunks; the latter two declarations could equally well be a
FOR loop with variable upper bound; or both sets of declarations could be
assignments to adjacent variables declared previously. Insertion of a
procedure call before the IF will certainly remove the problem; so may many
other small perturbations.
Bug 12: Found in CG 2.14 Fixed in CG 2.15
In code like
LET a = ...
LET b = field OF @a
it is possible for the code to extract the field to precede that loading the
value for a.
Bug 13: Found in CG 2.11 Fixed in CG 2.15
Code like
x!3 := .....
.... := x!3
(where there may be a sizeable gap between the two statements) may use
the old value of x!3 in the second statement.
Bug 14: Found in CG 2.15 Fixed in CG 2.16
The N option does not as it should control inclusion of procedure name strings
in compiled code.
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00000070 6c 69 65 72 20 76 65 72 73 69 6f 6e 73 20 6f 66 |lier versions of|
00000080 20 74 68 65 20 63 6f 6d 70 69 6c 65 72 2e 0a 0a | the compiler...|
00000090 0a 42 75 67 20 31 3a 09 46 6f 75 6e 64 20 69 6e |.Bug 1:.Found in|
000000a0 20 43 47 20 32 2e 31 30 09 09 09 20 20 20 46 69 | CG 2.10... Fi|
000000b0 78 65 64 20 69 6e 20 43 47 20 32 2e 31 31 0a 0a |xed in CG 2.11..|
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00000210 20 78 23 2b 31 20 20 79 6f 75 20 77 69 6c 6c 20 | x#+1 you will |
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00000230 54 68 65 20 63 6f 64 65 20 63 6f 6d 70 69 6c 65 |The code compile|
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00000250 70 72 65 73 73 69 6f 6e 20 69 73 20 74 68 65 20 |pression is the |
00000260 73 61 6d 65 20 61 73 20 62 65 66 6f 72 65 20 28 |same as before (|
00000270 6e 6f 20 63 6f 65 72 63 69 6f 6e 20 69 73 20 64 |no coercion is d|
00000280 6f 6e 65 29 2e 0a 0a 42 75 67 20 32 3a 09 46 6f |one)...Bug 2:.Fo|
00000290 75 6e 64 20 69 6e 20 43 47 20 32 2e 31 31 09 09 |und in CG 2.11..|
000002a0 09 20 20 20 46 69 78 65 64 20 69 6e 20 43 47 20 |. Fixed in CG |
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00000300 74 68 65 72 77 69 73 65 20 63 6f 6e 74 61 69 6e |therwise contain|
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00000350 79 20 62 65 20 63 6f 6d 70 69 6c 65 64 20 61 73 |y be compiled as|
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00000380 74 68 61 74 20 74 68 65 20 76 61 6c 75 65 20 6f |that the value o|
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000003e0 20 20 46 69 78 65 64 20 69 6e 20 43 47 20 32 2e | Fixed in CG 2.|
000003f0 31 33 0a 0a 41 6e 20 65 78 70 72 65 73 73 69 6f |13..An expressio|
00000400 6e 20 6f 66 20 74 68 65 20 66 6f 72 6d 20 20 28 |n of the form (|
00000410 70 2b 6b 29 21 28 6e 2a 71 29 2c 20 20 77 68 65 |p+k)!(n*q), whe|
00000420 72 65 20 6b 20 69 73 20 61 20 63 6f 6e 73 74 61 |re k is a consta|
00000430 6e 74 20 61 6e 64 20 6e 20 69 73 20 65 76 65 6e |nt and n is even|
00000440 0a 6d 61 79 20 62 65 20 63 6f 6d 70 69 6c 65 64 |.may be compiled|
00000450 20 61 73 20 69 66 20 69 74 20 77 65 72 65 20 20 | as if it were |
00000460 70 21 28 6e 2a 71 29 09 28 69 66 20 74 68 65 72 |p!(n*q).(if ther|
00000470 65 20 77 61 73 20 61 20 70 72 65 76 69 6f 75 73 |e was a previous|
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00000500 31 33 0a 0a 54 68 65 20 63 6f 64 65 20 67 65 6e |13..The code gen|
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00000d10 20 54 68 65 20 4c 20 6f 70 74 69 6f 6e 20 63 6f | The L option co|
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00000d40 73 20 6f 6e 20 62 79 20 64 65 66 61 75 6c 74 20 |s on by default |
00000d50 28 73 77 69 74 63 68 65 64 20 6f 66 66 20 62 79 |(switched off by|
00000d60 20 2e 2e 2e 20 2d 6f 70 74 20 2d 6c 29 2e 0a 0a | ... -opt -l)...|
00000d70 42 75 67 20 38 3a 20 46 6f 75 6e 64 20 69 6e 20 |Bug 8: Found in |
00000d80 43 47 20 32 2e 31 33 20 09 09 09 20 20 20 46 69 |CG 2.13 ... Fi|
00000d90 78 65 64 20 69 6e 20 43 47 20 32 2e 31 34 0a 0a |xed in CG 2.14..|
00000da0 54 68 65 20 72 65 73 75 6c 74 20 6f 66 20 61 2f |The result of a/|
00000db0 32 2c 20 77 68 65 72 65 20 61 20 69 73 20 6e 65 |2, where a is ne|
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00000dd0 32 2e 0a 0a 42 75 67 20 39 3a 20 46 6f 75 6e 64 |2...Bug 9: Found|
00000de0 20 69 6e 20 43 47 20 32 2e 31 34 20 09 09 09 20 | in CG 2.14 ... |
00000df0 20 20 46 69 78 65 64 20 69 6e 20 43 47 20 32 2e | Fixed in CG 2.|
00000e00 31 34 0a 0a 57 68 65 72 65 20 61 20 73 65 63 74 |14..Where a sect|
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00000e40 6f 66 29 20 53 54 41 54 49 43 0a 76 61 72 69 61 |of) STATIC.varia|
00000e50 62 6c 65 73 2c 20 54 41 42 4c 45 20 65 6c 65 6d |bles, TABLE elem|
00000e60 65 6e 74 73 20 61 6e 64 20 6e 75 6d 65 72 69 63 |ents and numeric|
00000e70 20 63 6f 6e 73 74 61 6e 74 73 20 74 6f 6f 20 6c | constants too l|
00000e80 61 72 67 65 20 74 6f 20 66 69 74 20 69 6e 74 6f |arge to fit into|
00000e90 20 61 20 44 50 0a 69 6e 73 74 72 75 63 74 69 6f | a DP.instructio|
00000ea0 6e 2c 20 74 68 65 20 63 6f 6d 70 69 6c 65 72 20 |n, the compiler |
00000eb0 6d 61 79 20 67 65 6e 65 72 61 74 65 20 61 6e 20 |may generate an |
00000ec0 69 6e 74 65 72 6e 61 6c 20 65 72 72 6f 72 20 6f |internal error o|
00000ed0 66 20 74 68 65 20 66 6f 72 6d 3a 0a 20 20 20 20 |f the form:. |
00000ee0 20 20 52 65 73 6f 6c 76 65 20 72 65 66 65 72 65 | Resolve refere|
00000ef0 6e 63 65 3a 20 6f 66 66 73 65 74 20 2e 2e 2e 20 |nce: offset ... |
00000f00 61 74 09 2e 2e 2e 2e 0a 0a 42 75 67 20 31 30 3a |at.......Bug 10:|
00000f10 20 46 6f 75 6e 64 20 69 6e 20 43 47 20 32 2e 31 | Found in CG 2.1|
00000f20 34 09 09 09 20 20 20 46 69 78 65 64 20 69 6e 20 |4... Fixed in |
00000f30 43 47 20 32 2e 31 35 0a 0a 46 75 72 74 68 65 72 |CG 2.15..Further|
00000f40 20 74 6f 20 39 2c 20 69 66 20 61 20 70 72 6f 63 | to 9, if a proc|
00000f50 65 64 75 72 65 20 69 73 20 6c 61 72 67 65 20 61 |edure is large a|
00000f60 6e 64 20 63 6f 6e 74 61 69 6e 73 20 6e 6f 20 75 |nd contains no u|
00000f70 73 65 20 6f 66 20 53 54 41 54 49 43 20 76 61 72 |se of STATIC var|
00000f80 69 61 62 6c 65 73 2c 0a 54 41 42 4c 45 73 20 6f |iables,.TABLEs o|
00000f90 72 20 73 74 72 69 6e 67 73 2c 20 62 75 74 20 64 |r strings, but d|
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00000fb0 6e 73 74 61 6e 74 73 2c 20 74 68 65 20 73 61 6d |nstants, the sam|
00000fc0 65 20 69 6e 74 65 72 6e 61 6c 20 65 72 72 6f 72 |e internal error|
00000fd0 20 6d 61 79 0a 6f 63 63 75 72 2e 0a 0a 42 75 67 | may.occur...Bug|
00000fe0 20 31 31 3a 20 46 6f 75 6e 64 20 69 6e 20 43 47 | 11: Found in CG|
00000ff0 20 32 2e 31 34 09 09 09 20 20 20 46 69 78 65 64 | 2.14... Fixed|
00001000 20 69 6e 20 43 47 20 32 2e 31 35 0a 0a 54 68 65 | in CG 2.15..The|
00001010 20 66 6f 6c 6c 6f 77 69 6e 67 20 73 6f 72 74 20 | following sort |
00001020 6f 66 20 63 6f 6e 73 74 72 75 63 74 0a 0a 20 20 |of construct.. |
00001030 20 4c 45 54 20 78 20 3d 20 2e 2e 2e 3b 0a 20 20 | LET x = ...;. |
00001040 20 4c 45 54 20 79 20 3d 20 2e 2e 2e 3b 0a 20 20 | LET y = ...;. |
00001050 20 49 46 20 2e 2e 2e 3c 23 78 31 32 33 34 20 54 | IF ...<#x1234 T|
00001060 48 45 4e 20 7b 0a 20 20 20 20 20 20 4c 45 54 20 |HEN {. LET |
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00001080 45 54 20 7a 7a 20 3d 20 2e 2e 2e 3b 0a 0a 6d 61 |ET zz = ...;..ma|
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00001340 74 20 74 68 65 20 66 69 65 6c 64 20 74 6f 20 70 |t the field to p|
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00001380 75 6e 64 20 69 6e 20 43 47 20 32 2e 31 31 09 09 |und in CG 2.11..|
00001390 09 20 20 20 46 69 78 65 64 20 69 6e 20 43 47 20 |. Fixed in CG |
000013a0 32 2e 31 35 0a 0a 43 6f 64 65 20 6c 69 6b 65 0a |2.15..Code like.|
000013b0 20 20 20 78 21 33 20 3a 3d 20 2e 2e 2e 2e 2e 0a | x!3 := ......|
000013c0 20 20 20 2e 2e 2e 2e 20 3a 3d 20 78 21 33 0a 28 | .... := x!3.(|
000013d0 77 68 65 72 65 20 74 68 65 72 65 20 6d 61 79 20 |where there may |
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000013f0 70 20 62 65 74 77 65 65 6e 20 74 68 65 20 74 77 |p between the tw|
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00001430 65 20 73 65 63 6f 6e 64 20 73 74 61 74 65 6d 65 |e second stateme|
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00001450 6e 64 20 69 6e 20 43 47 20 32 2e 31 35 09 09 09 |nd in CG 2.15...|
00001460 20 20 20 46 69 78 65 64 20 69 6e 20 43 47 20 32 | Fixed in CG 2|
00001470 2e 31 36 0a 0a 54 68 65 20 4e 20 6f 70 74 69 6f |.16..The N optio|
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00001490 20 73 68 6f 75 6c 64 20 63 6f 6e 74 72 6f 6c 20 | should control |
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000014b0 63 65 64 75 72 65 20 6e 61 6d 65 20 73 74 72 69 |cedure name stri|
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000014d0 63 6f 64 65 2e 0a |code..|
000014d6 
.