Thijs Koerselman

I'm struggling with some code, and found the following problem:

"pchlen*sizeof(char)" returns a different number than "sysmem_ptrsize(pch)".

Is this because pch is not a "t_ptr"? If so, am I writing bad code by using

regular pointers with the sysmem_ptr functions? I'm confused.

char *newline = "x0Dx0A"; // windows specific linebreak CR LF

post("ptrsize %ld", sysmem_ptrsize(pch));

if(mrk = sysmem_newptr(sysmem_ptrsize(pch)))

sysmem_copyptr(pch, mrk, sysmem_ptrsize(pch));

tmp = strtok(mrk, ","); // kick off the first element

I'm struggling with some code, and found the following problem:
"pchlen*sizeof(char)" returns a different number than "sysmem_ptrsize(pch)".
Is this because pch is not a "t_ptr"? If so, am I writing bad code by using
regular pointers with the sysmem_ptr functions? I'm confused.

        char * pch;
        char * tmp;
        char * mrk;
        long pchlen;
        long i;
        char *newline = "x0Dx0A"; // windows specific linebreak CR LF

        pch = strtok (*x->fdata, newline);
        pchlen = strlen(pch);

        post("strlen %ld", pchlen*sizeof(char));
        post("ptrsize %ld", sysmem_ptrsize(pch));

        if(mrk = sysmem_newptr(sysmem_ptrsize(pch)))
        {
            sysmem_copyptr(pch, mrk, sysmem_ptrsize(pch));
        }else{
            error("mem problem");
        }

        tmp = strtok(mrk, ","); // kick off the first element
        while(tmp = strtok(NULL, ","))
        {
            post ("column %s",tmp);
        }

sysmem_ptrsize

On Oct 27, 2006, at 11:10 AM, Thijs Koerselman wrote:

> I'm struggling with some code, and found the following problem: 

> "pchlen*sizeof(char)" returns a different number than 

> "sysmem_ptrsize(pch)". Is this because pch is not a "t_ptr"? If so, 

> am I writing bad code by using regular pointers with the sysmem_ptr 

While you shouldn't use sysmem_ptrsize() with pointers that you 

haven't explicitly allocated yourself with sysmem_newptr(), there's 

no reason to assume that strlen(p) == sysmem_ptrsize(p) even if you 

In this case, strlen(p) should report 3, sysmem_ptrsize(p) should 

When copying strings you should minimally use strlen()+1 for the 

string copy to account for the null terminated C string. Search 

online for more information regarding memory and strings in C.

> I'm struggling with some code, and found the following problem:   
> "pchlen*sizeof(char)" returns a different number than  
> "sysmem_ptrsize(pch)". Is this because pch is not a "t_ptr"? If so,  
> am I writing bad code by using regular pointers with the sysmem_ptr  
> functions? I'm confused.

While you shouldn't use sysmem_ptrsize() with pointers that you  
haven't explicitly allocated yourself with sysmem_newptr(), there's  
no reason to assume that strlen(p) == sysmem_ptrsize(p) even if you  
have. Take for instance the example:

In this case, strlen(p) should report 3, sysmem_ptrsize(p) should  
report 16.

When copying strings you should minimally use strlen()+1 for the  
string copy to account for the null terminated C string. Search  
online for more information regarding memory and strings in C.

Hi Joshua, thanks for for the detailed explanation. I get it now.

> On Oct 27, 2006, at 11:10 AM, Thijs Koerselman wrote:

> > I'm struggling with some code, and found the following problem:

> > "pchlen*sizeof(char)" returns a different number than

> > "sysmem_ptrsize(pch)". Is this because pch is not a "t_ptr"? If so,

> > am I writing bad code by using regular pointers with the sysmem_ptr

> While you shouldn't use sysmem_ptrsize() with pointers that you

> haven't explicitly allocated yourself with sysmem_newptr(), there's

> no reason to assume that strlen(p) == sysmem_ptrsize(p) even if you

> In this case, strlen(p) should report 3, sysmem_ptrsize(p) should

> When copying strings you should minimally use strlen()+1 for the

> string copy to account for the null terminated C string. Search

> online for more information regarding memory and strings in C.

On 10/28/06, Joshua Kit Clayton  wrote:
>
>
> On Oct 27, 2006, at 11:10 AM, Thijs Koerselman wrote:
>
> > I'm struggling with some code, and found the following problem:
> > "pchlen*sizeof(char)" returns a different number than
> > "sysmem_ptrsize(pch)". Is this because pch is not a "t_ptr"? If so,
> > am I writing bad code by using regular pointers with the sysmem_ptr
> > functions? I'm confused.
>
> While you shouldn't use sysmem_ptrsize() with pointers that you
> haven't explicitly allocated yourself with sysmem_newptr(), there's
> no reason to assume that strlen(p) == sysmem_ptrsize(p) even if you
> have. Take for instance the example:
>
> char *p = sysmem_newptr(16);
>
> sprintf(p,"boo");
>
> In this case, strlen(p) should report 3, sysmem_ptrsize(p) should
> report 16.
>
> When copying strings you should minimally use strlen()+1 for the
> string copy to account for the null terminated C string. Search
> online for more information regarding memory and strings in C.
>
> -Joshua
>
>