Re: unusable backtrace

[David Kastrup]

Werner LEMBERG <wl@gnu.org> writes:

> [782f5528e0, using a self-compiled, static version of Guile 2.2.7]
>
> While working on some LilyPond Scheme code I made a typo in file
> `define-markup-commands.scm`.  While executing `lilypond -V` (after
> `make install`) to process my `.ly` file I get the following
> backtrace.
>
> ```
>           19 (ly:book-process #<Book> #< Output_def> #< Output_def> #)
>           18 (ly:spacing-spanner::set-springs #<Grob SpacingSpanner >)
>           17 (ly:separation-item::calc-skylines #<Grob NonMusicalPap…>)
>           16 (ly:hara-kiri-group-spanner::pure-height #<Grob Vertic…> …)
>           15 (ly:axis-group-interface::adjacent-pure-heights #<Grob …>)
>           14 (ly:axis-group-interface::pure-height #<Grob BassFigur…> …)
>           13 (ly:axis-group-interface::pure-height #<Grob BassFigur…> …)
>           12 (ly:axis-group-interface::adjacent-pure-heights #<Grob …>)
>           11 (ly:grob::stencil-height #<Grob BassFigure >)
>           10 (ly:text-interface::print #<Grob BassFigure >)
>            9 (ly:text-interface::interpret-markup #< Output_def> (…) #)
> In ice-9/eval.scm:
>    298:42  8 (_ #(#(#<directory (lily) 1900780>) #< Output_def> (…) …))
> In unknown file:
>            7 (ly:text-interface::interpret-markup #< Output_def> (…) #)
> In ice-9/eval.scm:
>    293:34  6 (_ #(#(#<directory (lily) 1900780>) #< Output_def> (…) …))
> In unknown file:
>            5 (ly:text-interface::interpret-markup #< Output_def> (…) #)
> In ice-9/eval.scm:
>    293:34  4 (_ #(#(#(#(#<directory (lily) 1900780>) #< Out…> …) …) …))
>     159:9  3 (_ #(#(#(#(#<directory (lily) 1900780>) #< Out…> …) …) …))
>     263:9  2 (_ #(#(#(#(#<directory (lily) 1900780>) #< Out…> …) …) …))
>    223:20  1 (proc #(#(#(#(#<directory (lily) 1900780>) #< …> …) …) …))
> In unknown file:
>            0 (%resolve-variable (7 . arg) #<directory (lily) 1900780>)
> ```
>
> IMHO, this is completely useless.  There is not a single hint to the
> location of the error – why does Guile treat
> `define-markup-commands.scm` as an 'unknown file'?
>
> What am I missing?

That the error does not _occur_ in define-markup-commands.scm?
define-markup-command is a macro.  Apparently it was executed
successfully but leaving a faulty markup definition that blows up at the
time interpret-markup tries instantiating the markup in the current
output definition.  Since the macro has already executed successfully,
substituting different code for the original code, its connection to the
code that is now blowing up is no longer there.

-- 
David Kastrup