Tornado

Tornado 2.0
User’s Guide
After extended development sessions in Tornado shells, the cumulative memory
used for strings may be noticeable. If this is a problem, restart your target server.
5.3.9 Ambiguity of Arrays and Pointers
In a C expression, a nonsubscripted reference to an array has a special meaning,
namely the address of the first element of the array. The shell, to be compatible,
should use the address obtained from the symbol table as the value of such a
reference, rather than the contents of memory at that address. Unfortunately, the
information that the identifier is an array, like all data type information, is not
available after compilation. For example, if a module contains the following:
char string [ ] = "hello";
you might be tempted to enter a shell expression like:
➊
-> printf (string)
While this would be correct in C, the shell will pass the first 4 bytes of the string
itself to printf( ), instead of the address of the string. To correct this, the shell
expression must explicitly take the address of the identifier:
➋
-> printf (&string)
To make matters worse, in C if the identifier had been declared a character pointer
instead of a character array:
char *string = "hello";
then to a compiler ➊ would be correct and ➋ would be wrong! This is especially
confusing since C allows pointers to be subscripted exactly like arrays, so that the
value of string[0] would be “h” in either of the above declarations.
The moral of the story is that array references and pointer references in shell
expressions are different from their C counterparts. In particular, array references
require an explicit application of the address operator &.
5.3.10 Pointer Arithmetic
While the C language treats pointer arithmetic specially, the shell C interpreter
does not, because it treats all non-type-cast variables as 4-byte integers.
184