llvm dev - Jan 2011 - [LLVMdev] How to define a global variable?

Hi,

I'm trying to define a mutable variable, outside functions.  The code
below is trying to evaluate an expression much like "x = 1" at the
module level in Python.  It appears that when it tries to JIT the
function there is an error because there is no storage allocated for
'x'.   How do I do that?

thanks,
Rob

----- dumped IR -----
; ModuleID = 'repl-module'

%0 = type opaque

@x = external global %0*

define %0* @0() {
entry:
  store %0* inttoptr (i64 4316154480 to %0*), %0** @x
  ret %0* inttoptr (i64 4316154480 to %0*)
}
LLVM ERROR: Could not resolve external global address: x


----- C++ code -----
GlobalVariable *gvar = new GlobalVariable(*module, id_ty, false,
GlobalVariable::ExternalLinkage, 0, str.str());
Value *valv = gen_expr(val);
builder.CreateStore(valv, gvar, false);
...
engine->getPointerToFunction(thunk);

On 12 January 2011 22:28, Rob Nikander <rob.nikander at gmail.com>
wrote:
> @x = external global %0*
Hi Rob,

Try removing the 'extern', as it implies the variable storage is
elsewhere (ie. another object file).

cheers,
--renato

On Wed, Jan 12, 2011 at 6:08 PM, Renato Golin <rengolin at systemcall.org>
wrote:
> On 12 January 2011 22:28, Rob Nikander <rob.nikander at gmail.com>
wrote:
>> @x = external global %0*
>
> Hi Rob,
>
> Try removing the 'extern', as it implies the variable storage is
> elsewhere (ie. another object file).
>
I have to pass something from the LinkageTypes enum to the
constructor.  I tried others, like GlobalVariable::InternalLinkage,
which dumps as "internal global" but the error was the same.

Rob

On Wed, Jan 12, 2011 at 11:28 PM, Rob Nikander <rob.nikander at gmail.com>
wrote:
> I'm trying to define a mutable variable, outside functions.  The code
> below is trying to evaluate an expression much like "x = 1" at
the
> module level in Python.  It appears that when it tries to JIT the
> function there is an error because there is no storage allocated for
> 'x'.   How do I do that?
>
> ----- dumped IR -----
> ; ModuleID = 'repl-module'
>
> %0 = type opaque
>
> @x = external global %0*
First, replace %0* with a concrete type (like the i8* in your later post).
Then give @x an initializer. 'undef' is good enough if you don't
want
to assign an actual value yet. This should turn it into a definition
instead of a declaration.

On Thu, Jan 13, 2011 at 2:34 AM, Frits van Bommel <fvbommel at gmail.com>
wrote:
> On Wed, Jan 12, 2011 at 11:28 PM, Rob Nikander <rob.nikander at
gmail.com> wrote:
>
> First, replace %0* with a concrete type (like the i8* in your later post).
> Then give @x an initializer. 'undef' is good enough if you
don't want
> to assign an actual value yet. This should turn it into a definition
> instead of a declaration.
Thanks, the initializer did it.  Using opaque* works, at least in this
case; but I've replaced it with i8*.

Rob