Re: weakref miscompiling libgfortran

[Geoff Keating]

On 27/12/2005, at 3:36 PM, Jakub Jelinek wrote:

On Tue, Dec 27, 2005 at 02:20:44PM -0800, Geoff Keating wrote:

I'm not sure what "just fine" definition you're using here.  I don't
think you can say it's been extensively tested, and I'm fairly sure I
can find a bunch of bugs in it.  I have already filed one as <http://
gcc.gnu.org/bugzilla/show_bug.cgi?id=25140>; I understand that also
occurs on ELF targets.  I don't believe it's been tested with IMA

PR25140 talks about something common to all kinds of aliases (replace

result), so I don't know why you make a case against weakref from it.

`weakref' with `alias' or `weak, alias' and you'll get exactly the same

Well, there are two reasons:

1. Normally, with aliases, you only use one of the aliases in any given source file. With weakrefs, you are supposed to be able to use both, in fact it would be common to do so. 2. On Darwin aliases don't work at all, so I don't care how broken they would have been if they did work.

Weakrefs aren't really needed on Darwin for the purpose they have been
added, so they could very well just be unsupported there too (if the

it support weakrefs?).

target object file format doesn't support any kinds of aliases, why should

I think that's what I said below; the current implementation is really only for ELF targets. However, the general feature *is* useful on Darwin. We haven't yet hit a case where the libstdc++ headers would prefer to use a function defined only in a later Darwin version, and so would like to make it weak unless the user uses it directly, but in the future we probably will. Likewise, user C++ libraries might want to do the same thing. So, I'd like to see this work in 4.2. I think it actually does work on Darwin now in 4.2.

I would describe the version on the 4.1 branch as a hack that's to
work only for libgfortran on ELF targets, and that's OK; but that

version is not ready for general use. I'd like to see such a general-

It has nothing to do with libgfortran actually, libgfortran only ever
uses the weak pthread function aliases within libgfortran.

see PR4372, because unlike libgfortran or libobjc, libstdc++ installed
headers were using #pragma weak on all pthread_* functions it wanted
to use.

The reason why weakref attribute has been added is primarily libstdc ++,

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