HP SunSoft Pascal 4.0 Bedienungsanleitung PDF herunterladen (Seite 240)

216 Pascal 4.0 User’s Guide

A statement is considered to be reachable if there is a potential path of control,

even if it cannot be taken. Thus, no diagnostic is produced for the statement:

Thegoto Statement

Pascal detects and produces an error message about goto statements that

transfer control into structured statements—for example, for and while. It

does not allow such jumps, nor does it allow branching from the then part of

an if statement into the else part. Such checks are made only within the

body of a single procedure or function.

Uninitialized Variables

Pascal does not necessarily set variables to an initial value unless you explicitly

request that with the –Z option. The exception is static variables, which are

guaranteed to be initialized with zero values.

Because variable use is not tracked across separate compilation units, pc does

nothing about uninitialized or unused variables in global scope, that is, in the

main program. However, pc checks variables with local scope—those declared

in procedures and functions, to make sure they are initialized before being

used. pc ﬂags uninitialized variables with a warning message.

Unused Variables, Constants, Types, Labels, and Routines

If you declare a variable, constant, type, procedure, or function in local scope

but never use it, Pascal gives you a warning message. It does not do this for

items declared in global scope because you can use the items in a separately

compiled unit.

This error message is

generated when you compile

unreached.p.

hostname% pc unreached.p

Tue Feb 14 14:21:03 1995 unreached.p:

w 18630 line 8 - Unreachable statement

if false then

writeln('Impossible!')

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HP SunSoft Pascal 4.0 Bedienungsanleitung Seite 240