HP SunSoft Pascal 4.0 Uživatelský manuál stáhnout pdf (Strana 66)

42 Pascal 4.0 User’s Guide

The compiler issues warnings at the end of the procedure where the record

variables are deﬁned, that is, when some of the ﬁelds are deﬁnitely not set.

However, no warnings are issued if ﬁelds are used in the source before they are

initialized, as the control ﬂow may be different.

In some cases, it is not possible to determine at compile time whether the ﬁelds

have actually been initialized. For example:

• For the array variable V, whose elements are records, if any assignment of

the kind V[i]:= X or V[i].F:= Y occurs, the compiler considers the

corresponding ﬁelds of V[i] for all values of i to be initialized. If such a

ﬁeld is used, but not set, it is denoted as V[...].F in the warning message.

• All formal parameters are assumed to be initialized. Consequently, the

compiler does not perform any checking for these component ﬁelds.

With the -Rw option, the compiler takes into account built-in procedures which

initialize their argument variables, for example, reset(f) for the ﬁle buffer

variable f^ and its components. rewrite(f) does not initialize f^. The

compiler also examines ﬁeld handling inside WITH statements.

Use the -Rw option to check the use of “unsafe” variant records, such as the

assignment of a variant to a ﬁeld, or the use of another ﬁeld from a “parallel”

variant. These practices may result in runtime errors which are hard to ﬁnd.

Note – The -Rw option requires extra compile-time, and is, therefore,

recommended for use in debugging only.

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HP SunSoft Pascal 4.0 Uživatelský manuál Strana 66