[M3devel] TextLiteral.MaxBytes again

[Rodney M. Bates]

On 06/16/2015 03:43 AM, Jay K wrote:
> er..the proposal was old, but nevertheless..
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> From: jay.krell at cornell.edu
> To: hosking at cs.purdue.edu; rodney_bates at lcwb.coop
> CC: m3devel at elegosoft.com
> Subject: RE: [M3devel] TextLiteral.MaxBytes again
> Date: Tue, 16 Jun 2015 08:43:10 +0000
>
> I must have missed this. I commited the "-15" solution. But this proposal sounds better. I need to revisit.. Thank you.
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>

If you do this, there are a number of places that should be reviewed for
fallout.  I think something in runtime has some hard-coded value, and
several places there and in pickles use TextLiteral.  Plus probably a
few tests around.  Actually, these should probably be looked at even
with the latest change, tho' the latter would not require introduction
of unsafe code.


>
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> From: hosking at cs.purdue.edu
> Date: Thu, 5 Sep 2013 12:05:07 -0400
> To: rodney_bates at lcwb.coop
> CC: m3devel at elegosoft.com
> Subject: Re: [M3devel] TextLiteral.MaxBytes again
>
> Here is a modest proposal that should resolve this issue.
> Declare TextLiteral.T to have a minimal buf: ARRAY [0..0] OF Byte;
> Then use UNSAFE address arithmetic to access the bytes (TextLiteral.m3 already does the bounds checks explicitly using cnt).
>
> Updated TextLiteral.i3 and TextLiteral.m3 attached.
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>
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> Antony Hosking | Associate Professor | Computer Science | Purdue University 305 N. University Street | West Lafayette | IN 47907 | USA Mobile +1 765 427 5484 On Sep 5, 2013, at 10:42 AM, "Rodney M. Bates" wrote: > There is another issue here. I want TextLiteral.MaxBytes to get a final size > and not change. Every time it changes, it creates compatibility problems by > orphaning any existing pickle files and any compiled programs that write them. > It changes the fingerprint, so a recently-compiled reading program can't find the > type in its own list of known types. This also affects network objects when two > communicating programs are compiled with different TextLiteral versions. > > MaxBytes' particular contribution to the type doesn't otherwise matter, because it's > artificial, but it still undermines reading pickles. > > I have been loading up the pickle reading code with hard-coded historical fingerprints > of various older versions. But it's a pain to keep doing,
> tedious to ferret out the > values, and it still only helps those who constantly download and compile the latest > CM3. > > At some point, I am thinking of choosing some likely historical TextLiteral.T fingerprint > and hard-coding the compiler to artificially deliver it , rather than the one computed from > the version-of-the day of TextLiteral. But this too would not help those who would > rather not constantly download the latest, rebuild the compiler, then recompile their > applications. > > On 09/03/2013 01:02 AM, Jay K wrote: >> ok, another question: >> >> >> CONST >> (* DIV BITSIZE should not be here! *) >> (* MaxBytes = LAST (INTEGER) DIV BITSIZE (Byte) - 7 - 8 * ORD(BITSIZE(INTEGER) = 64); *) >> MaxBytes = 16_7FFFFFFF DIV BITSIZE (Byte) - 7 - 8 * ORD(BITSIZE(INTEGER) = 64); >> >> TYPE >> T = RTHooks.TextLiteral; >> REVEAL >> T = TEXT BRANDED "TextLiteral.T" OBJECT >> cnt : INTEGER; >> buf : ARRAY [0..MaxBytes - 1] OF Byte; >> OVERRIDES ... >> >> >> T is a reference
> type. >> Is there a way to state this with no limit? >> >> >> Isn't it already unsafe? >> You know -- the array is usually smaller and the compiler is only going to check against this large size. >> >> >> - Jay >

-- 
Rodney Bates
rodney.m.bates at acm.org