On Tuesday, November 11, 2014 at 11:53 AM, Mark Pizzolato wrote:
> On Tuesday, November 11, 2014 at 12:45 AM, Cory Smelosky wrote:
> [...]
> > > It looks like you are having isues witg word size. Your machine
> > > seems
> > confusef about word size issues. I386 amd64 and x86?_64 all sem ro
> > show up.
> > >
> >
> > Hmmm, strange it only appears in the (probably-less-maintained)
> simulators.
> > ;););)
[...]
> Actually, the PC complaints are name collisions with readline components
> which are dynamically loaded. It seems that some readline dependent
> libraries export a variable PC which collides with the PC defined in the
> simulator. Since scp's use of readline usage is very simple, I'm pretty sure
> that the existence of the name collision doesn't actually cause a problem.
>
> This issue will occur with any simulator which has a global variable PC
> defined.
> Many/most simulators have a PC register, but this is often defined as a macro
> which refers to an element of an array:
> For example, the PDP11 has:
> #define PC R[7]
> In this case, there is no global variable called PC which exists in the linker
> observed name space, and thus no warning happens when readline is
> dynamically loaded at simulator startup.
>
> I believe that this is completely safe to ignore.
Umm... Urrr... Well...
Actual usage of a simulator with a global variable named PC shows that my
statement: "I believe that this is completely safe to ignore." was WRONG and
the warning about the size is really just the tip of the iceberg. All
simulators which have a global variable called PC will have operational issues
when readline is dynamically loaded EVEN IF no warning is issued. This affects
other platforms beyond OpenBSD as well.
As it turns out, about 10 of the 42 current simulator binaries are affected by
this.
The relatively easy fix is a one line addition to the simname_defs.h file to
avoid the issue:
#define PC PC_Global /* Rename of global PC variable to
avoid namespace conflicts on some platforms */
This avoids the problem without making wholesale changes to any other source
modules. The only downside is that if a simulator developer is using a
symbolic debugger, any references made to examine the variable from the
debugger must use the PC_Global name instead of PC. Since most of these
simulators are relatively mature, running under a symbolic debugger is a
relatively rare activity these days.
I've checked in the above change to all the relevant simulators.
- Mark
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