Re: Basic c question again - type casting

On 14/06/2008, at 12:55 AM, Lim Hock-Chai wrote:

Funny enough, I read an article yesterday that talks about c programmer
should try to avoid using typedef.

Why? Is it on-line? Do you have a link?

The reason that I use typedef is because the moduleName and locationID
should actually be a fix 10 char long variables. The logMessage should
actually be a varying length field of 2048 char long. So, to force all
caller to obey this rule, I used typedef and this was what it looked
like originally:
typedef struct {
char value[10];
} logECD_STP3_piModuleName_T;

typedef struct {
char value[32766];
} logECD_STP3_piLocationID_T;

typedef struct {
unsigned short l;
char a[2048];
} logECD_STP3_piLogMessage_T

That's a good use of typedef even though it's weird from a C programmer's perspective. You are indicating that the interface is not a "normal" C null-terminated string but something else so pay attention.

But I soon found out that c doesn't allow passing literal to a char
array parameter (<= Not programmer friendly).

Yes it does. As long as the prototype is correct. For example:

#include <stdio.h>
void func( char * );
void main( void )
{
char * text = "test data";
func( text );
func( "more test data" );
return;
}
void func( char * data )
{
printf( "%s\n", data );
return;
}

You can see the second call to func passes a string literal. The reason it didn't work for you was because the types were incompatible.

So I change it to use char * and left the typedef (lazy me).

Yep, but char* is not the right approach either.

Regards,
Simon Coulter.
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