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<div class="moz-cite-prefix">On 1/24/25 8:38 AM, Hairy Pixels via
fpc-pascal wrote:<br>
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<blockquote type="cite"
cite="mid:CAGsUGt=gdVYi2cpBdgtSdUVOwZ116m6EOifBsDXoCgCM8RYFRw@mail.gmail.com">
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<div dir="ltr" class="gmail_attr">On Jan 24, 2025 at 1:34:26 PM,
Nikolay Nikolov via fpc-pascal <<a
href="mailto:fpc-pascal@lists.freepascal.org"
moz-do-not-send="true" class="moz-txt-link-freetext">fpc-pascal@lists.freepascal.org</a>>
wrote:<br>
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<blockquote class="gmail_quote"
style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"
type="cite"> Doesn't matter whether they're handled in the
same scope or not. It's the same code. Usually they're not
handled in the same scope, but in a very distant place. That's
usually when exceptions are convenient.<br>
Once you let them bubble up you need to wrap all call sites
with try..finally right?<br>
Wrong. Only sites that allocate memory, that needs to be
freed, before leaving the scope need a try..finally. You don't
need to wrap every call. That's nonsense. The pattern is:<br>
<br>
var<br>
<br>
{... initialize local vars you're going to allocate in this
function with nil}<br>
<br>
begin<br>
<br>
try<br>
<br>
{lots of code, allocations, calls, etc}<br>
<br>
finally<br>
<br>
{cleanup code}<br>
<br>
{free stuff that isn't nil}<br>
<br>
end;<br>
<br>
end;<br>
<br>
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Yes that’s what I meant. If you don't know which calls could fail
you need to wrap all functions that allocate memory in
try..finally. That’s what the original post was commenting on, the
need for some other syntax which knows to free a variable if the
function terminates early due to an exception, like the implicit
exception frames for managed types like dynamic arrays.<br>
</blockquote>
<p>Yes, that could probably save some typing, however it comes at a
price:</p>
<p>1) only works for classes</p>
<p>2) not obvious order of destructor calls. What if they have side
effects, and the order matters?</p>
<p>3) doesn't support procedural APIs.</p>
<p>In really, I find try..finally to be much nicer, because you can
do a proper cleanup in the finally section that includes any of
the following:</p>
<p>* destructor calls</p>
<p>* FreeMem</p>
<p>* Dispose</p>
<p>* function calls (e.g. Close(), XFree(), etc.)<br>
</p>
<p>And the order is well defined by you.</p>
<p>So, I prefer try..finally. And it's not much typing, when used
properly.</p>
<p>Nikolay<br>
</p>
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