newlisp and libcaca

[konrad]

Hi all

I'm trying to get libcaca (an Ascii basically just the basic tutorial that can be found at:

http://linux.die.net/man/3/tutorial

However i get a segfault at the line " caca_refresh_display(dp);"

running an strace shows : gettimeofday({1189337045, 203711}, NULL) = 0

I've tried running the program with and without the refresh line (not having a refresh means that there is not so much of the output but there are no significant differences in the strace before the failure point.

Note I tried compiling the example in C and it works fine on its own. Anyone have any ideas on what to try next in debugging this, I'd really like to get libcaca working with newLisp.

regards

Konrad

[pjot]

It seems that the variable 'dp' is a pointer to some memory. If it is used wrongly your program may crash.

Therefore, could you show us your newLisp implementation?

Peter

[konrad]

Here is my code:

Code: Select all

(context 'CUCUL)
(set 'libcucul "/usr/lib/libcucul.so")
(set 'funcs '(
             "cucul_create_canvas"
             "cucul_set_color_ansi"
             "cucul_putstr"
             ))

(dolist (func funcs)
  (import libcucul func))

(set 'consts '(
              ("BLACK" 0x00)
              ("WHITE" 0x0f)))

(dolist (const consts)
  (constant (sym (const 0)) (const 1)))

(context 'CACA)
(set 'libcaca "/usr/lib/libcaca.so")
(set 'funcs '(
             "caca_create_display"
             "caca_set_display_title"
             "caca_refresh_display"
             ))

(dolist (func funcs)
  (import libcaca func))



(context 'MAIN)

(set 'cv (CUCUL:cucul_create_canvas 0 0))
(set 'db (CACA:caca_create_display cv))
(CACA:caca_set_display_title db "Hello!")
(CUCUL:cucul_set_color_ansi cv CUCUL:BLACK CUCUL:WHITE)
(CUCUL:cucul_putstr cv 0 0  "This is a message")
(CACA:caca_refresh_display dp)

[pjot]

Hi,

Your last line shows:

Code: Select all

(CACA:caca_refresh_display dp)

But where do you set the variable 'dp'? It has no value assigned and therefore the contents of 'dp' is nil.

According to the original C program at the link you provided above, the variable 'dp' should be set as follows:

Code: Select all

dp = caca_create_display(cv);

However, in your program you use variablename 'db' instead of 'dp'.

Peter

[konrad]

Yes Er that will be it.

I don't know how many times i've spend ages trying to debug a typo,

so here is another example. dp is what I had meant to xall the variable not db. Using longer names like display would have probably saved me on this one : )

regards

Konrad

[konrad]

Well that works. The next trick is to capture events. Not to do this the C code

1) creates a variable based on a structure
2) passes the address of the structure into a function so it can be written too.

I assume that I need to

(set 'ev (pack ...))

to get a correct event symbol and then I need to unpack the results for reading?

would this be about the correct take on this ?

I have a feeling this is going to be a little clunky as the C definition contains a union.

regards

Konrad.

[pjot]

To read C-structures in newLisp is explained here:

http://www.newlisp.org/CodePatterns.html#extending


Maybe it helps.

Regards
Peter