Re: TreeStore behavior with -malign-double

[Bryan Silverthorn <bsilvert arlut utexas edu>]

Murray Cumming wrote:
> On Tue, 2006-07-11 at 15:02 -0500, Bryan Silverthorn wrote:
> > To summarize: TreeStore columns with custom data types do not correctly 
> > store their values. I'm assuming that gtk+ and gtkmm were not compiled 
> > with -malign-double, and that the problem is therefore a direct result 
> > of the binary compatibility issues introduced by -malign-double.
>
>
> That sounds very likely. In general you need to be very careful when
> using compiler options. What's the purpose of this one for you?

In this case, it was one of the default flags applied by our build tool, 
and I removed it once I ran into this issue. My impression is that the 
flag is a fairly common optimization for modern x86 machines, but is 
never necessary, and can definitely cause binary incompatibility.

So it's not an issue that will block anyone's project (assuming that 
it's not, in fact, a library bug), but it's an easy-to-hit gotcha that 
can lead to silently incorrect library behavior. It might be nice if 
this incompatibility could be made more visible if present (eg, a 
warning printed by gtkmm init), but I'm not sure how. A quick glance at 
the gcc manual doesn't reveal any obvious way (eg, a macro) to test for 
the flag's presence.

Mostly, I just wanted to point out the issue for the benefit of future 
generations. And google.

--
Bryan Silverthorn <bsilvert cs utexas edu>