read errors

read errors

[Han-Wen Nienhuys]

I just added some friendly error messages to the reader. I haven't
committed it yet, though. -- I have the following comment now. Perhaps
someone can shed some light on the proper way to deal with errors?


/*
  Give meaningful error messages for errors

  We use the format

  MESSAGE
  This happened in ....

  This is not standard GNU format, but the test-suite likes the real
  message to be in front.

  Hmmm.

  Maybe this is a kludge? Perhaps we should throw (list EXPR FILENAME
  LINENO COLUMNO), and have the exception handler sort out the error
  message? Where does the handler live, what are the conventions for
  the expression argument of the handler? How does this work for an
  error message like

Backtrace:
In standard input:
   4: 0* [list ...

standard input:4:1: While evaluating arguments to list in expression (list a b):standard input:4:1: Unbound variable: a
ABORT: (unbound-variable)


  In any case, we would have to assemble that information anyway. 
 */

#define  INPUT_ERROR(port, message, arg) { 									\
      char s[1024];\
      int fn_found =  SCM_STRINGP (SCM_FILENAME(port));\
      char *fn = "";\
      if (fn_found)\
         fn = SCM_STRING_CHARS(SCM_FILENAME(port));\
      snprintf (s, 1024, "%s\nThis happened in %s%s%s line %d column %d", message, \
		fn_found ? "`" : "", \
		fn,\
		fn_found ? "'" : "", \
	       SCM_LINUM(port) + 1, SCM_COL(port) + 1);			\
      SCM_MISC_ERROR(s, arg);											\
    }

-- 

Han-Wen Nienhuys   |   hanwen@cs.uu.nl   |   http://www.cs.uu.nl/~hanwen 

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Re: read errors

[Marius Vollmer]

Han-Wen Nienhuys <hanwen@cs.uu.nl> writes:

>   This is not standard GNU format, but the test-suite likes the real
>   message to be in front.

We need to change the test-suite, then.

>   Maybe this is a kludge?

No, I think it's the best we can do with the present system.

> #define  INPUT_ERROR(port, message, arg) {

Does this have to be a macro?  I would like it better to be a function
(like scm_misc_error) and a thinly wrapped function (like
SCM_MISC_ERROR).

>       snprintf (s, 1024, "%s\nThis happened in %s%s%s line %d column %d", message,

Can we use scm_simple_format here?  That would avoid the 1024 limit
and would also feel more gentle since we don't need to poke into the
strings private parts.

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Re: read errors

[Han-Wen Nienhuys]

marius.vollmer@uni-dortmund.de writes:
> >   This is not standard GNU format, but the test-suite likes the real
> >   message to be in front.
> 
> We need to change the test-suite, then.

OK.

> > #define  INPUT_ERROR(port, message, arg) {
> 
> Does this have to be a macro?  I would like it better to be a function
> (like scm_misc_error) and a thinly wrapped function (like
> SCM_MISC_ERROR).
 
I followed the SCM_MISC_ERROR template here.  BTW, is misc-error some
kind of standard, or can we have 'read-error as a key?

> >       snprintf (s, 1024, "%s\nThis happened in %s%s%s line %d column %d", message,
> 
> Can we use scm_simple_format here?  That would avoid the 1024 limit
> and would also feel more gentle since we don't need to poke into the
> strings private parts.

I'll check it out.


-- 

Han-Wen Nienhuys   |   hanwen@cs.uu.nl    | http://www.cs.uu.nl/~hanwen/


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Re: read errors

[Han-Wen Nienhuys]

marius.vollmer@uni-dortmund.de writes:
> >   Maybe this is a kludge?
> 
> No, I think it's the best we can do with the present system.

ok.

> >       snprintf (s, 1024, "%s\nThis happened in %s%s%s line %d column %d", message,
> 
> Can we use scm_simple_format here?  That would avoid the 1024 limit
> and would also feel more gentle since we don't need to poke into the
> strings private parts.

Yep, done, committed. (Scheme beginner, didn't know about
simple-format.)


--
Han-Wen Nienhuys   |   hanwen@cs.uu.nl   |   http://www.cs.uu.nl/~hanwen 

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Re: read errors

[Marius Vollmer]

Han-Wen Nienhuys <hanwen@cs.uu.nl> writes:

> Yep, done, committed. (Scheme beginner, didn't know about
> simple-format.)

Thanks!

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Re: read errors

[Marius Vollmer]

Han-Wen Nienhuys <hanwen@cs.uu.nl> writes:

> I followed the SCM_MISC_ERROR template here.  BTW, is misc-error some
> kind of standard, or can we have 'read-error as a key?

We certainly can use 'read-error as the key and I think it would be a
good idea.

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