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">//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 Expand


(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 Expand


(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 Expand


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





Maybe it helps.



Regards

Peter