[NB: someone needs to write up a decent FAQ entry about this. Memory
allocation and the distinction between arrays and pointers are
probably the most widely misunderstood aspects of C programming.]
Torbjørn Kristoffersen wrote:
> > This allocates precisely one byte of data for dbQuery. Try
> >
> > char dbQuery[1024];
>
> I replied to this mail too, but then I used char *dbQuery instead.
> What's the difference anyway?
Assuming that dbQuery is a local (automatic) variable in all the
following cases:
char dbQuery[1024] = "";
allocates an array of 1024 characters on the stack at run time, and
initialises it to the empty string (i.e. sets dbQuery[0] to '\0').
dbQuery is effectively a constant (typically it's an offset from the
frame pointer) which equates to the address of the first character.
char dbQuery[] = "";
is similar, but it only allocates enough memory for the specified
string (i.e. 1 byte).
char *dbQuery = "";
will allocate one byte of memory at compile time in the .rodata
segment (which holds read-only data such as string literals). It will
also allocate a pointer (i.e. `sizeof(char *)' bytes of data) on the
stack at run time, and initialise that pointer with the address of the
string literal.
In this case, dbQuery refers to the pointer, and &dbQuery would be a
constant (i.e. an offset from the frame pointer).
--
Glynn Clements <[EMAIL PROTECTED]>
