HP 3000 Manuals HP 3000 Manuals
Practices to Avoid
To make a program portable, you need to minimize machine dependencies.
The following are programming practices you should avoid to ensure
portability:
* Using dollar signs ($) in identifiers.
* Using underscores (_) as the first character in an identifier.
* Using sized enumerations.
* Reliance on implicit expression evaluation order.
* Making assumptions regarding storage allocation and layout.
* Dependence on the number of significant characters in an
identifier. Identifiers should differ as early as possible in the
name. ANSI C requires that the first 31 characters of an internal
name are significant. Only the first 6 characters of an external
name are required to be significant by ANSI C.
* Dereferencing null pointers.
* Dependence on pointer representation.
* Dependence on being able to dereference a pointer to an object
that is not correctly aligned.
* Dependence on the ability to store a pointer in a variable of type
int.
* Dependence on case distinctions in external names.
* Dependence on char being signed or unsigned.
* Dependence on bitwise operations in signed integers.
* Dependence on bit-fields of any type except int, unsigned int, or
signed int.
* Dependence on the sign of the remainder in integer division.
* Dependence on right shifts of negative signed values.
* Dependence on more than six declarators modifying a basic type.
* Dependence on values of automatic variables after a longjmp call
when the values were changed between the setjmp and longjmp calls.
* Dependence on being able to call setjmp within an arbitrarily
complex expression.
* Dependence on file system characteristics.
* Dependence on string literals being modifiable.
* Dependence on extern declarations within a block being visible
outside of the block.