bug#38388: [2.9.5] Inaccurate source location info for unbound variables

bug#38388: [2.9.5] Inaccurate source location info for unbound variables

[Ludovic Courtès]

Hello,

I have a test that runs ‘guix system build’ on this file:

--8<---------------cut here---------------start------------->8---
(use-modules (gnu))                                   ; 1
(use-service-modules networking)                      ; 2

(operating-system                                     ; 4
  (host-name "antelope")                              ; 5
  (timezone "Europe/Paris")                           ; 6
  (locale "en_US.UTF-8")                              ; 7

  (bootloader (GRUB-config (target "/dev/sdX")))      ; 9
  (file-systems (cons (file-system
                        (device (file-system-label "root"))
                        (mount-point "/")
                        (type "ext4"))
                      %base-file-systems)))
--8<---------------cut here---------------end--------------->8---

Here, ‘GRUB-config’ is unbound, and the test expects to see a stack
frame corresponding to line 9.

However, the stack frame we get is for line 11, char 32, which
corresponds to (file-system-label "root").

So it would seem that the IP-to-source-location mapping is not quite
working as expected.

Thoughts?

Ludo’.

bug#38388: [2.9.5] Inaccurate source location info for unbound variables

[Andy Wingo]

Hi,

On Tue 26 Nov 2019 16:20, Ludovic Courtès <ludovic.courtes@inria.fr> writes:

> I have a test that runs ‘guix system build’ on this file:
>
> (use-modules (gnu))                                   ; 1
> (use-service-modules networking)                      ; 2
>
> (operating-system                                     ; 4
>   (host-name "antelope")                              ; 5
>   (timezone "Europe/Paris")                           ; 6
>   (locale "en_US.UTF-8")                              ; 7
>
>   (bootloader (GRUB-config (target "/dev/sdX")))      ; 9
>   (file-systems (cons (file-system
>                         (device (file-system-label "root"))
>                         (mount-point "/")
>                         (type "ext4"))
>                       %base-file-systems)))
>
> Here, ‘GRUB-config’ is unbound, and the test expects to see a stack
> frame corresponding to line 9.
>
> However, the stack frame we get is for line 11, char 32, which
> corresponds to (file-system-label "root").
>
> So it would seem that the IP-to-source-location mapping is not quite
> working as expected.
>
> Thoughts?

What version is this with?

Unfortunately as you know, bare identifiers don't have good source
location information.  There are small improvements that can be made but
larger improvments are gnarly.  Could be this is a case for a small
improvement though!

Andy

bug#38388: [2.9.5] Inaccurate source location info for unbound variables

[Ludovic Courtès]

Hello!

Andy Wingo <wingo@igalia.com> skribis:

> On Tue 26 Nov 2019 16:20, Ludovic Courtès <ludovic.courtes@inria.fr> writes:
>
>> I have a test that runs ‘guix system build’ on this file:
>>
>> (use-modules (gnu))                                   ; 1
>> (use-service-modules networking)                      ; 2
>>
>> (operating-system                                     ; 4
>>   (host-name "antelope")                              ; 5
>>   (timezone "Europe/Paris")                           ; 6
>>   (locale "en_US.UTF-8")                              ; 7
>>
>>   (bootloader (GRUB-config (target "/dev/sdX")))      ; 9
>>   (file-systems (cons (file-system
>>                         (device (file-system-label "root"))
>>                         (mount-point "/")
>>                         (type "ext4"))
>>                       %base-file-systems)))
>>
>> Here, ‘GRUB-config’ is unbound, and the test expects to see a stack
>> frame corresponding to line 9.
>>
>> However, the stack frame we get is for line 11, char 32, which
>> corresponds to (file-system-label "root").
>>
>> So it would seem that the IP-to-source-location mapping is not quite
>> working as expected.
>>
>> Thoughts?
>
> What version is this with?

The wrong location info is with 2.9.5.  2.2.x (and 2.0.x) work fine.

Any idea where I should poke for debugging?

> Unfortunately as you know, bare identifiers don't have good source
> location information.  There are small improvements that can be made but
> larger improvments are gnarly.  Could be this is a case for a small
> improvement though!

I know, that’s why this test checks a favorable case (symbol wrapped in
an sexp).  So I agree this would be a welcome improvement, but I think
it’s unnecessary for the purposes of the use case above.

Thanks,
Ludo’.

bug#38388: [2.9.5] Inaccurate source location info for unbound variables

[Andy Wingo]

On Thu 28 Nov 2019 09:20, Ludovic Courtès <ludovic.courtes@inria.fr> writes:

>>> I have a test that runs ‘guix system build’ on this file:
>>>
>>> (use-modules (gnu))                                   ; 1
>>> (use-service-modules networking)                      ; 2
>>>
>>> (operating-system                                     ; 4
>>>   (host-name "antelope")                              ; 5
>>>   (timezone "Europe/Paris")                           ; 6
>>>   (locale "en_US.UTF-8")                              ; 7
>>>
>>>   (bootloader (GRUB-config (target "/dev/sdX")))      ; 9
>>>   (file-systems (cons (file-system
>>>                         (device (file-system-label "root"))
>>>                         (mount-point "/")
>>>                         (type "ext4"))
>>>                       %base-file-systems)))
>>>
>>> Here, ‘GRUB-config’ is unbound, and the test expects to see a stack
>>> frame corresponding to line 9.
>>>
>>> However, the stack frame we get is for line 11, char 32, which
>>> corresponds to (file-system-label "root").
>
> Any idea where I should poke for debugging?

Sure would be nice to reduce the test case!  Once you have reduced it, I
would first look at the result of ,expand on this form.  If it looks the
same as in 2.2, then perhaps the CPS layer is at fault.  Could be we're
dropping an important source location somewher.

Andy

bug#38388: [2.9.5] Inaccurate source location info for unbound variables

[Ludovic Courtès]

Hi,

Ludovic Courtès <ludovic.courtes@inria.fr> skribis:

> I have a test that runs ‘guix system build’ on this file:
>
> (use-modules (gnu))                                   ; 1
> (use-service-modules networking)                      ; 2
>
> (operating-system                                     ; 4
>   (host-name "antelope")                              ; 5
>   (timezone "Europe/Paris")                           ; 6
>   (locale "en_US.UTF-8")                              ; 7
>
>   (bootloader (GRUB-config (target "/dev/sdX")))      ; 9
>   (file-systems (cons (file-system
>                         (device (file-system-label "root"))
>                         (mount-point "/")
>                         (type "ext4"))
>                       %base-file-systems)))
>
> Here, ‘GRUB-config’ is unbound, and the test expects to see a stack
> frame corresponding to line 9.
>
> However, the stack frame we get is for line 11, char 32, which
> corresponds to (file-system-label "root").

I can’t say I got to the bottom of why we got this weird line number,
but commit d3a775ff10cbd0e14af38d6f900a7538db89bd90 solves this specific
issue.

Ludo’.