<br><br><div class="gmail_quote">On Wed, Jul 6, 2011 at 8:28 PM, David T. Lewis <span dir="ltr"><<a href="mailto:lewis@mail.msen.com">lewis@mail.msen.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div class="im"><br>
On Wed, Jul 06, 2011 at 06:38:10PM -0700, Eliot Miranda wrote:<br>
><br>
> On Wed, Jul 6, 2011 at 6:31 PM, Igor Stasenko <<a href="mailto:siguctua@gmail.com">siguctua@gmail.com</a>> wrote:<br>
><br>
> ><br>
> > With a new version of plugin submitted by Eliot it no longer crashing :)<br>
> ><br>
><br>
> Slang is occasionally super-tricky. If you write<br>
><br>
> self atexit: #sendSignalToPids<br>
><br>
> it generates<br>
><br>
> atexit("sendSignalToPids")<br>
><br>
> which will crash. You must write<br>
><br>
> self atexit: #sendSignalToPids asSymbol<br>
><br>
> to get it to generate<br>
><br>
> atexit(sendSignalToPids)<br>
><br>
> (where sendSignalToPids is some function to be called at exit).<br>
><br>
> If course we should change this but there's backwards-compatibility for<br>
> plugin to consider. Does anyone depend on the old behavior? I've been<br>
> bitten more than a few times by this. Sigh...<br>
<br>
</div>Symbols and strings are used more or less interchangably in C translation<br>
(aka "slang") and in pragmas. </blockquote><div><br></div><div>Not so. Strings and symbols are only used interchangeably in type declarations and these can be put in pragmas. So</div><div><br></div><div><span class="Apple-tab-span" style="white-space:pre"> </span><var: #theFP type: #'char *'></div>
<div><br></div><div>is equivalent to</div><div><br></div><div><span class="Apple-tab-span" style="white-space:pre"> </span><var: 'theFP' type: 'char *'></div><div><br></div><div>since Slang merely transcribes the characters in either the string or symbol.</div>
<div><br></div><div>But in code a symbol should be different to a string. A string should translate to a string, and a symbol should translate to a name. e.g. in </div><div><br></div><div> self sizeof: #SQFile</div><div>
<br></div><div>it is really dumb of Slang to translate this as sizeof("SQFile"). Since we're always talking about literal symbols and literal strings it is always possible for the programmer to use a literal string where they mean there to be a string, and not a symbol. Further, this change would not affect any of the existing uses of symbols and strings for type declarations.</div>
<div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">So I think that there is a general expectation<br>
that either a symbol or a string would translate to C as a string.</blockquote><div><br></div><div>I disagree. Its a historical accident that we should agree to clean-up.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
In<br>
the case of #sendSignalToPids, this is actually a function pointer that<br>
is being used in a rather specialized context.</blockquote><div><br></div><div>A context which arises throughout the VM with indirect function calls, with sizes of types, etc. </div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
So even though the<br>
translation of 'self atexit: #sendSignalToPids' produces a surprising<br>
result in this case, I would still say that is reasonable to expect<br>
Smalltalk symbols and strings to both translate into C strings, and<br>
it would not be reasonable to expect a simple C translator to do<br>
enough type checking to figure out that in this particular case the<br>
'#sendSignalToPids' should be treated as a function pointer rather<br>
than as a string.<br></blockquote><div><br></div><div>I disagree. But I've been using the #asSymbol workaround since I want consensus before making any change.</div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<br>
The original method in UnixOSProcessPlugin is written as follows in<br>
order to avoid this issue:<br>
<br>
self cCode: 'atexit(sendSignalToPids)'.<br></blockquote><div><br></div><div>This isn't a good approach since one can neither look for senders of #atexit: nor #sendSignalToPids, nor can one simulate its execution. In general the use of a string argument to cCode: should be ruthlessly stamped out whereever possible.</div>
<div><br></div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<br>
I also note that the purpose of SlangBrowser is to make it easy to<br>
review code like this while it is being written, so I guess that I<br>
should get off my butt and get this working in the oscog branch one<br>
of these days :-/<br>
<br>
Dave<br>
<br>
</blockquote></div><br><br clear="all"><br>-- <br>best,<div>Eliot</div><br>