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Subject: 
Re: Some goals, ideas, etc. for a new bytecode interpreter (long)
Newsgroups: 
lugnet.robotics.rcx
Date: 
Mon, 10 May 1999 18:04:12 GMT
Viewed: 
1480 times
  
Kekoa Proudfoot wrote:

Mark Tarrabain  <markt@lynx.bc.ca> wrote:

Although technically every instruction could be a legitimate breakpoint,
in practice, the only breakpoints in a program would be at the first
instruction for a given source line (since a single line of source code
may map to more than a single instruction).

Some people might want to step through the disasm, no?  Especially if they
do not yet trust the compiler.

Single-stepping through instructions would be a mode offered by the
interpreter, and wouldn't require any breakpoints to be set.  I suppose what
the debugging information could contain is, instead of a list of valid
breakpoints, a list of file/line number,and function ID for each instruction
in the program  (The latter piece of information being able to be used by a
high level language debugger to locate a set of valid identifiers within the
current scope).  That would mean that the debugging information size would be
8 times the number of instructions contained in the program: 2 bytes for the
file [an index into an array of files for the program]), 2 bytes for function
ID (an index into an array of functions), and 4 bytes for the line number (I
realize that in practice for such small programs, only 2 bytes may be
necessary for line numbers, but since the source file will exist on a desktop
PC, it could conceivably be much longer than 64K [eg. lots of whitespace, or
perhaps very long comment sequences].)

Mark



Message is in Reply To:
  Re: Some goals, ideas, etc. for a new bytecode interpreter (long)
 
(...) Sure, but that's what zero padding is for. Since the opcode is IR-only, you don't care too much about length. The only length restriction comes from the second digit of the opcode, assuming you're using the ROM to receive incoming IR data. (...) (25 years ago, 10-May-99, to lugnet.robotics.rcx)

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