On Mon, May 7, 2012 at 12:21 PM, Steven Schveighoffer
<schveiguy@yahoo.com> wrote:
On Mon, 07 May 2012 12:59:24 -0400, Andrew Wiley <wiley.andrew.j@gmail.com> wrote:
On Mon, May 7, 2012 at 8:42 AM, Steven Schveighoffer <schveiguy@yahoo.com>wrote:
On Mon, 07 May 2012 09:27:32 -0400, Alex Rønne Petersen <
That's exactly what storing the interface in the object file does. You
don't need the source because the object file contains the compiler's
interpretation of the source, and any inferred properties it has discovered.
Putting inferred purity into an object file sounds like a bad idea. It's
not hard to imagine this scenario:
-function foo in libSomething is inferred as pure (but not declared pure by
the author)
-exeSomethingElse is compiled to use libSomething, and the compiler takes
advantage of purity optimizations when calling foo
-libSomething is recompiled and foo is no longer pure, and exeSomethingElse
silently breaks
no, it just doesn't link.
Purity inference is fine for templates (because recompiling the library
won't change the generated template code in an executable that depends on
it), but in all other cases, the API needs to be exactly what the author
declared it to be, or strange things will happen.
I agree that's the case with the current object/linker model. Something that puts inferred properties into the object file needs a new model, one which does not blindly link code that wasn't compiled from the same sources.
Then all you've done is to make attributes the author can't control part of the API, which will force library users to recompile their code more often for non-obvious reasons. Avoiding that is one of the points of shared libraries.
I think we're actually talking about different contexts. I'm speaking in the context of shared libraries, where I think the API needs to be exactly what the author requests and nothing more. With object files, static libraries, and static linking, I agree that this sort of thing could work and wouldn't cause the same problems because it's impossible to swap the library code without recompiling/relinking the entire program.