[Ecls-list] Segmentation faults/detected access to ...address

[Juan Jose Garcia-Ripoll]

I do not have time for a longer answer right now but note two things:

- Segmentation faults in arbitrary code can not be graciously handled by
ECL. Instead it just looks for the outermost CATCH_ALL statement and jumps
there. Since there is no such statement surrounding c_string_to_object(), it
just quits.

- puts() accesses the content of its argument. if you use puts(obj ==
OBJNULL) it is like using puts(1) which tries to access the memory location
(char*)1 causing a segmentation fault or an access violation -- it depends
on the OS.

Juanjo

On Sat, Mar 13, 2010 at 5:08 PM, Seth Burleigh <seth at tewebs.com> wrote:

> So, i decided that I would try to get a c REPL going which would also
> catch any errors with incorrectly entered code (not go into the
> debugger). Cool stuff , ecl:)
> Anyways, I found that whenever I entered an statement which would
> generate an error, like the letter a, the program exits with a
> segmentation fault. Im not exactly sure why entering an invalid
> statement would generate one. I was also wondering if ecl was supposed
> to catch all segmentation faults which resuled from lisp code executing
> inside of it? According to this:
> http://ecls.sourceforge.net/new-manual/re41.html
> SIGSEGV should be caught automatically? I noticed that if i used
> cl_eval, everything would work, it would just go into the debugger.
> Also, I noticed that if i uncommented the code below it would produce a
> "Detected acccess to an invalid or protected memory address" and would
> throw me into the lisp debugger. I know this has something to do with
> 'puts' expecting a constant char* while the statement obj==OBJNULL
> returns an int, but I would like to understand what exactly is causing
> this error.
>
> Heres the code:
>
> #include <ecl/ecl.h>
> #include <stdio.h>
> #include <string.h>
>
> int main(int argc, char **argv)  {
>  cl_boot(argc, argv);
>  cl_env_ptr env = ecl_process_env();
>  while (1) {
>    printf(">>");
>    int nbytes = 100;
>    char *str = (char*)malloc(nbytes);
>    getline(&str,&nbytes,stdin);
>    if (strcmp(str,"exit\n")==0 ) {
>      break;
>    }
>
>    cl_object obj = c_string_to_object(str);
>
>    //uncommented code below produced unprotected access error
>    //puts(obj==OBJNULL);
>
>    CL_CATCH_ALL_BEGIN(env) {
>      cl_object evaled = cl_safe_eval(obj,(cl_object)env,Cnil);
>      cl_pprint(1,evaled);
>    } CL_CATCH_ALL_IF_CAUGHT {
>      puts("ERROR");
>    } CL_CATCH_ALL_END;
>  }
>  cl_shutdown();
> }
>
>
>
>
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-- 
Instituto de Física Fundamental, CSIC
c/ Serrano, 113b, Madrid 28006 (Spain)
http://juanjose.garciaripoll.googlepages.com
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