[Patch Darwin] proposal for a 4.6 work-around to dsymutil calling issues.

[Mike Stump]

On Dec 2, 2010, at 3:45 AM, IainS wrote:
> PR43751 and PR46749 show that we have a problem with the existing way in which dsymutil is called by trying to recognize that the c/l contains a source file.

So, you propose to just remove the feature and break one of the fundamental usage models of compilation on unix environments, because....

Help me flesh out the remainder of that sentence.

> Not only do we not cover all source types,

We could add support for more source types, if we cared.  Initially Apple only did the C family of languages because that was product and dsymutil wasn't tested with other languages (and might not work).

> but the whole thing breaks down with relatively benign changes in the c/l.

And those bugs I'd posit, can be fixed.

> AFAICT, we don't really have a suitable facility to:
> 'determine that a source is present for the set of supported languages and insert a flag'

When the compilation backend (cc1, cc1plus) of a language is called, trivially, a source is present.  gcc.c knows when a source is present, because it calls the compiler.  Further, it know when it is creating an intermediate .o file that will then be removed during compilation.  Is there any information it doesn't have?

> I have not yet written doc for this - pending comments on whether it's considered a reasonable work-around for 4.6.

Nope...  I prefer the status quo over completely breaking the unix compilation model.