[Crash-utility] fix gdb_get_datatype cannot handle integer type

[Dave Anderson]

----- Original Message -----
> Dave,
> 
> On Wed, Mar 6, 2013 at 10:04 PM, Dave Anderson <anderson at redhat.com>
> wrote:
> >
> >
> > ----- Original Message -----
> >> Hi Dave,
> >>
> >> Current when pass integer type to gdb_get_datatype in crash, it would return
> >> req->typecode=0 and req->length=0.
> >>
> >> As it only allow TYPE_CODE_ENUM to be passed. here is a patch for fixing it.
> >> Do you think it could be merged?
> >
> > That's the OP_VAR_VALUE section -- what is the command that you're using that
> > ends up passing an integer type to the function?  And what problem does it
> > cause?
> 
> I enhance whatis command in my local code base to show the function's original variant name.
> If not with my change, the original result is: 
> int schedule_delayed_work_on(int , struct delayed_work * , long unsigned int );
> With my change, the result becomes:
> int schedule_delayed_work_on(int cpu, struct delayed_work * dwork, long unsigned int delay);
> 
> So it look nicer, right? :)

I guess -- but when I add the patch, it doesn't look any different, so presumably
it only applies w/respect to your enhanced whatis command...

> 
> But I meet an issue that whatis is not intent for showing function prototype only, but for
> structure/union/integer type.
> 
> So I need to add arg_to_datatype in whatis_variable to tell the passed data's type to whether
> call gdb's function for exacting out the function parameter's name.
> 
> Then I face the bug as I reported...

It's not really a bug because that code path was meant for usage by the 
enumerator_value() function.  So it makes me a bit nervous to modify it 
for code that only your enhanced whatis command would ever see.   

Would your code work if only the req->typecode and req->length fields where
passed back?  (i.e., without tinkering with the req->value and req->tagname
fields in the non-enum case?)  Like this:

--- gdb-7.3.1/gdb/symtab.c.orig
+++ gdb-7.3.1/gdb/symtab.c
@@ -5054,8 +5054,9 @@ gdb_get_datatype(struct gnu_request *req
 		if (gdb_CRASHDEBUG(2))
         		console("expr->elts[0].opcode: OP_VAR_VALUE\n");
 		type = expr->elts[2].symbol->type;
+		req->typecode = TYPE_CODE(type);
+		req->length = TYPE_LENGTH(type);
 		if (TYPE_CODE(type) == TYPE_CODE_ENUM) {
-			req->typecode = TYPE_CODE(type);
 			req->value = SYMBOL_VALUE(expr->elts[2].symbol);
 			req->tagname = TYPE_TAG_NAME(type);
 			if (!req->tagname) {

And what exactly do you pass to datatype_info() that would lead to
that code path?

Dave