Problems with structures in S-Lang

[Goran Koruga <goran.koruga@xxxxxxxxx>]

Hi,

I encountered some problems using structures in S-Lang. I would be glad
if anyone could please explain the difference between the working and non-
working example for me.

Here are the relevant pieces of the code I'm using :

------ non working example
#include <sys/time.h>
#include <unistd.h>

/* man page for gettimeofday() says (the acutal definition uses int
   instead of long, but int = long on Linux)
   struct timeval {
       long tv_sec;
       long tv_usec;
   };
*/

static struct timeval *Msl_timestamp; /* it's malloc'd in main() */

/* here's the definition of the structure for S-Lang */
static SLang_IStruct_Field_Type timeval_struct[] =
{
    MAKE_ISTRUCT_FIELD(struct timeval, sec,  "sec",  SLANG_UINT_TYPE, 1),
    MAKE_ISTRUCT_FIELD(struct timeval, usec, "usec", SLANG_UINT_TYPE, 1),
    SLANG_END_TABLE
};

/* we add the structure this way */
SLadd_istruct_table(timeval_struct, (VOID_STAR) &Msl_timestamp, "timestamp");

/* here's how I set it */
void  Msl_set_timestamp(void)
{
    gettimeofday(Msl_timestamp, NULL);
}

/* my program crashes whenever I access members of the timestamp variable
   in S-Lang */
sprintf("%d %d", timestamp.sec, timestamp.usec);

Note that I have tried to use various S-Lang defined types to access the
members of the timestamp structure, but the result was always the same.
------ end of non working example


Here's the working example :

------ working example
/* I added a new C structure for this case */
typedef struct timeval_struct
{
    unsigned int sec;
    unsigned int usec;
} timeval_elt;

timeval_elt  *Msl_timestamp = NULL;  /* it's malloc'd in main() */

/* here's the definition of the structure for S-Lang */
static SLang_IStruct_Field_Type timeval_struct[] =
{
    MAKE_ISTRUCT_FIELD(timeval_elt, sec,  "sec",  SLANG_UINT_TYPE, 1),
    MAKE_ISTRUCT_FIELD(timeval_elt, usec, "usec", SLANG_UINT_TYPE, 1),
    SLANG_END_TABLE
};

/* we add the structure this way */
SLadd_istruct_table(timeval_struct, (VOID_STAR) &Msl_timestamp, "timestamp");

/* here's how I set it */
void  Msl_set_timestamp(void)
{
    static struct timeval timestamp;

    gettimeofday(&timestamp, NULL);
    Msl_timestamp->sec = timestamp.tv_sec;
    Msl_timestamp->usec = timestamp.tv_usec;
}
/* my program works whenever I access members of the timestamp variable
   in S-Lang */
sprintf("%d %d", timestamp.sec, timestamp.usec);
------ end of working example

Thanks in advance,
Goran
--

Writing about music is like dancing about architecture.
    -- Frank Zappa