bug#16357: insufficient print abbreviation in error messages

[Andy Wingo <wingo@pobox.com>]

Not really sure what to do here.

Ideally we could just use ~@y in the format messages.  However we can't
rely on having a full format loaded up, only simple-format.  We could
lazily load the full format when needed, but I don't know if we should
train users that the full `format' is always around.

We could define well-known parameters for specifying that we should
truncate the output of a `write' procedure, and have pair / vector /
bytevectors use that parameter when needed.  Perhaps that's the thing?

Or, we could use print states.  But print states are not so great and
ideally we would remove them eventually.

Thoughts?

Andy

On Mon 06 Jan 2014 00:00, Zefram <zefram@fysh.org> writes:

> When guile is constructing error messages that display offending objects,
> in version 2.0.9 it never abbreviates long or deep structures.  This can
> easily lead to pathologically-long messages that take stupid amounts of
> time and memory to construct and to display.  By contrast, guile-1.8
> applies abbreviation at a reasonable level, and objects appearing in
> stack traces have reasonable abbreviation on both versions.  Two very
> mild examples:
>
> $ guile-1.8 --debug -c "(read (let aaa ((n 100) (v '())) (if (= n 0) v (aaa (- n 1) (cons n v)))))"
> Backtrace:
> In current input:
>    1: 0* [read {(1 2 3 4 5 6 7 8 9 ...)}]
>
> <unnamed port>:1:1: In procedure read in expression (read (# 100 #)):
> <unnamed port>:1:1: Wrong type argument in position 1 (expecting open input port): (1 2 3 4 5 6 7 8 9 10 ...)
> $ guile-2.0 --debug -c "(read (let aaa ((n 100) (v '())) (if (= n 0) v (aaa (- n 1) (cons n v)))))"
> Backtrace:
> In ice-9/boot-9.scm:
>  157: 7 [catch #t #<catch-closure d68400> ...]
> In unknown file:
>    ?: 6 [apply-smob/1 #<catch-closure d68400>]
> In ice-9/boot-9.scm:
>   63: 5 [call-with-prompt prompt0 ...]
> In ice-9/eval.scm:
>  432: 4 [eval # #]
> In unknown file:
>    ?: 3 [call-with-input-string "(read (let aaa ((n 100) (v '())) (if (= n 0) v (aaa (- n 1) (cons n v)))))" ...]
> In ice-9/command-line.scm:
>  180: 2 [#<procedure c83ac0 at ice-9/command-line.scm:175:6 (port)> #<input: string b495b0>]
> In unknown file:
>    ?: 1 [eval (read (let aaa (# #) (if # v #))) #<directory (guile-user) d5cc60>]
>    ?: 0 [read (1 2 3 4 5 6 7 8 9 ...)]
>
> ERROR: In procedure read:
> ERROR: In procedure read: Wrong type argument in position 1 (expecting open input port): (1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100)
> $ guile-1.8 --debug -c "(read (let aaa ((n 100) (v '())) (if (= n 0) v (aaa (- n 1) (cons v n)))))"
> Backtrace:
> In current input:
>    1: 0* [read {(((# . 3) . 2) . 1)}]
>
> <unnamed port>:1:1: In procedure read in expression (read (# 100 #)):
> <unnamed port>:1:1: Wrong type argument in position 1 (expecting open input port): (((((((# . 7) . 6) . 5) . 4) . 3) . 2) . 1)
> $ guile-2.0 --debug -c "(read (let aaa ((n 100) (v '())) (if (= n 0) v (aaa (- n 1) (cons v n)))))"
> Backtrace:
> In ice-9/boot-9.scm:
>  157: 7 [catch #t #<catch-closure 1c71400> ...]
> In unknown file:
>    ?: 6 [apply-smob/1 #<catch-closure 1c71400>]
> In ice-9/boot-9.scm:
>   63: 5 [call-with-prompt prompt0 ...]
> In ice-9/eval.scm:
>  432: 4 [eval # #]
> In unknown file:
>    ?: 3 [call-with-input-string "(read (let aaa ((n 100) (v '())) (if (= n 0) v (aaa (- n 1) (cons v n)))))" ...]
> In ice-9/command-line.scm:
>  180: 2 [#<procedure 1c89da0 at ice-9/command-line.scm:175:6 (port)> #<input: string 1a505b0>]
> In unknown file:
>    ?: 1 [eval (read (let aaa (# #) (if # v #))) #<directory (guile-user) 1c65c60>]
>    ?: 0 [read (((# . 3) . 2) . 1)]
>
> ERROR: In procedure read:
> ERROR: In procedure read: Wrong type argument in position 1 (expecting open input port): ((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((() . 100) . 99) . 98) . 97) . 96) . 95) . 94) . 93) . 92) . 91) . 90) . 89) . 88) . 87) . 86) . 85) . 84) . 83) . 82) . 81) . 80) . 79) . 78) . 77) . 76) . 75) . 74) . 73) . 72) . 71) . 70) . 69) . 68) . 67) . 66) . 65) . 64) . 63) . 62) . 61) . 60) . 59) . 58) . 57) . 56) . 55) . 54) . 53) . 52) . 51) . 50) . 49) . 48) . 47) . 46) . 45) . 44) . 43) . 42) . 41) . 40) . 39) . 38) . 37) . 36) . 35) . 34) . 33) . 32) . 31) . 30) . 29) . 28) . 27) . 26) . 25) . 24) . 23) . 22) . 21) . 20) . 19) . 18) . 17) . 16) . 15) . 14) . 13) . 12) . 11) . 10) . 9) . 8) . 7) . 6) . 5) . 4) . 3) . 2) . 1)
>
> Debian incarnation of this bug report:
> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=734128
>
> -zefram