Re: [PATCH 2/5] annotations: Add position information to various calls

[David Gibson <david-xT8FGy+AXnRB3Ne2BGzF6laj5H9X9Tb+@public.gmane.org>]

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On Mon, Jan 15, 2018 at 10:28:38AM +0100, Julia Lawall wrote:
> 
> 
> On Mon, 15 Jan 2018, David Gibson wrote:
> 
> > On Thu, Jan 11, 2018 at 04:21:44PM +0100, Julia Lawall wrote:
> > > > > +	old_node->srcpos = srcpos_copy_all(new_node_begin_srcpos);
> > > >
> > > > This doesn't seem right.  Replacing the old position with the new
> > > > makes sense for indivudal properties where the whole value is also
> > > > replaced.  But for nodes we really need to track both locations.
> > > >
> > > > I think the extra complexity here is why I didn't add this tracking
> > > > earlier.
> > >
> > > I have the following example:
> > >
> > > /dts-v1/;
> > >
> > > / {
> > >         #address-cells = < 1 >;
> > >         #size-cells = < 1 >;
> > >
> > >         tree_1: soc@0 {
> > >         	reg = <0x0 0x0>;
> > >         };
> > >
> > >         foo: foo_node {
> > >                 prop_1: added-prop = <0x99>;
> > >         };
> > >
> > >         bar_node {
> > >                 added-prop = <0x77>;
> > >         };
> > >
> > > };
> > >
> > > /include/ "test_b1.dts"
> > > /include/ "test_c1.dts"
> > >
> > > -------------------
> > >
> > > Then test_b1.dts and test_c1.dts are both /include/ "test_d.dts".  And
> > > test_d.dts is:
> > >
> > > / {
> > >         foo_node {
> > >                 added-prop = <0x1 0x2 0x3>;
> > >         };
> > >
> > >         foo_node {
> > >                 added-prop = <0x1 0x2 0x3>;
> > >         };
> > >
> > >         bar: bar_node {
> > >                 added-prop = <0x5>;
> > >         };
> > > };
> > >
> > > ----------
> > >
> > > The point of the example is that via the includes there are tw ways to
> > > reach test_d.dts.
> > >
> > > Accordingly, by accumulating a list of positions in merge_nodes, I end up with:
> > >
> > > /dts-v1/;
> > >
> > > / { /* tests/test_d.dts:1, tests/test_d.dts:1, tests/test_a.dts:10 */
> > > 	#address-cells = <0x1>; /* tests/test_a.dts:11 */
> > > 	#size-cells = <0x1>; /* tests/test_a.dts:12 */
> > >
> > > 	tree_1: soc@0 { /* tests/test_a.dts:14 */
> > > 		reg = <0x0 0x0>; /* tests/test_a.dts:15 */
> > > 	}; /* tests/test_a.dts:16 */
> > >
> > > 	foo: foo_node { /* tests/test_d.dts:6, tests/test_d.dts:2, tests/test_d.dts:6, tests/test_d.dts:2, tests/test_a.dts:18 */
> > > 		prop_1: added-prop = <0x1 0x2 0x3>; /* tests/test_d.dts:7 */
> > > 	}; /* tests/test_d.dts:8, tests/test_d.dts:4, tests/test_d.dts:8, tests/test_d.dts:4, tests/test_a.dts:20 */
> > >
> > > 	bar: bar_node { /* tests/test_d.dts:10, tests/test_d.dts:10, tests/test_a.dts:22 */
> > > 		added-prop = <0x5>; /* tests/test_d.dts:11 */
> > > 	}; /* tests/test_d.dts:12, tests/test_d.dts:12, tests/test_a.dts:24 */
> > > }; /* tests/test_d.dts:13, tests/test_d.dts:13, tests/test_a.dts:26 */
> > >
> > > --------
> > >
> > > For example, in the last line, we see tests/test_d.dts:13 twice, because it
> > > is merged in twice.  Is this what is wanted?  Should it be there only once?
> > > Should there be some indication on how tests/test_d.dts:13 is reached?
> > > This is a fake example, but I saw some examples with duplicated positions
> > > in the Linux kernel code.
> >
> > Right, that's ugly, but it's not that easy to fix.  Really we'd need
> > to merge/overlap each element in the list to accumulate them.  Going
> > back to the original proposal isn't a solution though because of cases
> > like this, which will be much more common that duplicated includes:
> >
> > / {
> > 	foo {
> > 		compatible = "...";
> > 		reg = < .. >;
> > 		ranges = < ... >;
> > 		lots = ...;
> > 		of = ...;
> > 		other = ...;
> > 		properties = ...;
> > 	};
> > }
> >
> > &{/foo} {
> > 	one-tiny-change = "yes";
> > };
> >
> > The original proposal would annotate the output with *only* the
> > location of the one-tiny-change, which is extremely misleading.  Much
> > worse than duplicated locations.
> 
> It's only the label on the braces that is affected.  compatible, reg, etc
> should still have their original locations.

Sure, it'll be ok if the errors are able to reference a specific
property.  But we can't really count on that - it seems likely that
there will be errors which refer to a node, but can't really point at
a specific property as the problem.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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