Copyright (c) Compaq Computer Corporation 1997, 2001. All rights reserved.

PRODUCT:  DIGITAL DEC PL/I for OpenVMS Alpha, Versions 4.0-5, 4.1-1

OP/SYS:   Compaq OpenVMS Alpha, Version 6.2 through 7.1

SOURCE:   Compaq Computer Corporation


SYMPTOM:

The PL/I compiler's code optimizer generates PLIG-I-UNREACH messages.
The informational messages occur even if the optimizer cannot guarantee
the value of a variable that is evaluated in an IF-THEN-ELSE sequence
(where both the IF and ELSE cases return() from the procedure).

Consider the following example that demonstrates the reported behavior:

     $ TYPE TEST.PLI
     tmp:procedure (switch) returns(fixed) ;
     dcl switch fixed ;
     if switch = 0 then return(0); else return(1);
     end tmp;

     $ PLI TEST

     if switch = 0 then return(0); else return(1);
     ^
     %PLIG-I-UNREACH, code can never be executed at label
     at line number 3 in file user:[directory]TEST.PLI;4

     %PLIG-I-SUMMARY, Completed with 0 errors, 0 warnings, and
                     1 informational messages.

NOTE:  The VAX PL/I for OpenVMS VAX compiler's code optimizer does not
       generate %PLIG-I-UNREACH messages for this code.


COMPAQ RESPONSE:

Support for this product is now provided by the third party vendor,
KEDNOS at (831)373-7003.


WORKAROUNDS:

The following workarounds can be used to resolve the problem:

     1. Specify the /WARN=NOINFO qualifier to suppress the informational
        message.

     2. Specify the /NOOPTIMIZE qualifier to disable optimization options.

     3. Modify the code to separate the IF and ELSE statements (code
        beyond the IF statement is not unreachable).  For example:

             $ TYPE TEST.PLI
             tmp:procedure (switch) returns(fixed) ;
             dcl switch fixed ;
             if switch = 0 then return(0);
             return(1);
             end tmp;


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