Den 15-02-2011 19:31, Jonas Maebe skrev:
On 15 Feb 2011, at 19:01, Jeppe Johansen wrote:
What about allowing a new keyword "weak" and let it have two forms(something
like you suggested back in one of the mails from 12th january)? Name mangling is an issue
of course. It would be easiest to handle if weak symbols simply weren't name
mangled(something like cdecl and co)
weakexternal can already be combined with cdecl. weak+external could also be combined with cdecl.
As an aside, cdecl is not the same as "no mangling". It means "mangle the same as
the C compiler", which varies from platform to platform.
procedure TestProc; weak; // This produces a weak symbol
begin
end;
procedure TestProc2; weak default 'SomeDefaultFunction'; // Weak+default makes
the declaration external by default
procedure TestProc3; weak default 'SomeDefaultFunction'; external name
'Test_TestProc3'; // Overcome eventual name mangling problems. Symbol is called
Test_TestProc3 and is linked to SomeDefaultFunction if not resolved at linktime
procedure TestProc4; weak; external; // Replaces/does the same as weakexternal
I don't understand why you again propose to change the meaning of "external name 'xxx'"
for weak symbols. As I mentioned in my previous mail, for consistency reasons something like that
will not be done. I also don't see the advantage of inventing a new syntax ("weak
default") when existing modifiers can already express the required semantics.
I don't propose changes. I might just formulate it in a way that make it
seem so. Actually, if you go by the example in your previous mail you
would have to change the meaning of "external name 'xxx'" external name
'xxx'; means that you "change" the name of an unresolved symbol into xxx
so function calls to that procedure will go to xxx(and in that way make
it an unresolved symbol). In your example you used external name
'NoHandler'; which of course will be resolved, and all the weak stuff
will be ignored
.weak xxx
will then mark an unresolved weak
.set xxx, NoHandler
will then make a weak symbol point to NoHandler if it can't be resolved
The problem I have with the alias solution is that to practically use it
you would have to change the way alias works weak symbols. Alias simply
declares an extra global label, it doesn't invoke .set
You might also note the problem in the example
// a) on Linux
// .weak P$TestProc
// .set P$TestProc, NoHandler
// .weak TestProc
// .set TestProc, NoHandler
If you then somewhere else defines TestProc, then yes, calls to the
assembler symbol TestProc will resolve to TestProcHandler. But if you
call TestProc directly, in the pascal sense, then it would call
P$TestProc which hasn't been overriden and thus points to NoHandler
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