Kednos PL/I for OpenVMS VAX
Release Notes for Version 3.8

Two new preprocessor commands %LIST" and "%NOLIST, have been added, to affect the generation of listing data specified by the command line. These commands are treated the same way as %LIST_ALL ana %NOLIST_ALL, respectively.

4.3.7 PL/I V3.5 Now Allows A Default FIXED BINARY Size To Be Selected.

A new compiler command switch has been added to allow the default size of a FIXED BINARY to be set to either 15, or 31. The default size is FIXED_BINARY=31. The following is the command syntax:

PLI/FIXED_BINARY[=option] option 15 - Sets the default size of fixed binary to 15. 31 - Sets the default size of fixed binary to 31. This is the default if the qualifier is present without a value or if the qualifier is omitted.

4.3.8 PL/I V3.5 LTRIM, And RTRIM Builtins

The LTRIM, and RTRIM builtin functions are subsets of the compiler TRIM builtin function.

The TRIM function can trim blanks or other characters from the left or right of a given string. TRIM requires three arguments to accomplish this. The first argument is the input string, the second argument specifies the characters to be trimmed from the left of the input, and the third argument specifies the characters to be trimmed from the right of the input. If either the second or third argument is a null string, no characters are removed from the corresponding end of the input string.

LTRIM has two arguments, the same first two arguments of the TRIM builtin.

RTRIM has two arguments, the same as the first and third argument to the TRIM builtin.

When only the first argument is supplied to the LTRIM, or RTRIM builtin functions, white space will be removed from the left or right side respectively.

4.3.9 PL/I V3.5 DEFINED Statement

The usage rules for the DEFINED statement have been relaxed to allow you to define a variable over another variable having a dissimilar data type. If the compiler detectes this, a warning message may be issued, and the variables involved may not be optimized.

4.3.10 PL/I V3.5 Asterisk Subscripts When Referencing An Entire Array

Arrays may now be assigned using asterisks as subscripts. The current usage of asterisks for declaring arrays passed as parameters remains the same; new additional functionality is now available to allow non pointer qualified array assignments.

4.3.11 PL/I V3.5 ADDREL Builtin

The ADDREL builtin is a function that takes a pointer as its first argument, an integer expression as its second argument, and returns a pointer which is the sum of the two arguments.

4.3.12 PL/I V3.5 BYTESIZE Builtin

The BYTESIZE builtin is equivalent to the SIZE builtin. This has been added to for compatibility with other PL/I compilers.

4.3.13 PL/I V3.5 /ALIGN

A new compiler switch has been added to allow for data alignment for RISC machine data types. The syntax:

PLI/ALIGN /ALIGN - will align structures and aligned bit strings as shown in the following table. /NOALIGN - normal alignment. This is the defualt. DATA TYPE ALIGNMENT ---------------------------------------------------------- fixed bin (p) p <= 7 byte fixed bin (p) 7 < p < =15 word fixed bin (p) p > 15 longword fixed dec (p,q) word float bin (p) p <= 24 longword float bin (p) 24 < p <= 53 quadword float bin (p) p > 53 octaword float dec (p) p <= 7 longword float dec (p) 7 < p <= 15 quadword float dec (p) p > 15 octaword char byte char aligned byte char varying word bit bit bit aligned longword pointer longword label quadword entry quadword file longword structure max of members picture byte offset longword area longword

4.4 INSTALLATION NOTES

4.4.1 Installation Of The DECwindows Compiler Interface

Do you want to install the DECwindows Compiler Interface for VAX PL/I [YES]?

Answering YES will result in the installation of the DECwindows Compiler Interface for VAX PL/I. See Section 3.3 in these release notes for more information.

4.4.2 Compression Of PLI$STARLET.TLB

Starting with PL/I V2.3, the system interface library (PLI$STARLET.TLB) has been shipped in compressed library format, which reduces the amount of space required to store the library but increases the amount of time required to access and retrieve a component of the library, such as a system service declaration. If you use PLI$STARLET.TLB heavily and you have disk space available, you may want to decompress the library during the installation when the question is asked. If you decide that you want to decompress it after having installed the compressed version, you can use the following command to decompress the library:

$ LIBRARY/DATA=EXPAND/OUTPUT=SYS$COMMON:[SYSLIB] - SYS$COMMON:[SYSLIB]PLI$STARLET.TLB

The decompressed form of the library is slightly over twice the size of the compressed version.

4.4.3 Coexistence With VAX PL/I V2.n

If VAX PL/I V3.5 is installed on a system that already has a version of VAX PL/I older than V3.0 installed, none of the files in the older version are superseded, because the files on the version 3 kit all have different names. The version 3 compiler is the default compiler once it is installed. The only action required to switch between using the version 3 compiler and a pre-version 3 compiler is to define the PLI$COMPILER logical name to point to the compiler image to use. For example, if you want to use an older version of the compiler in a single process, you can use the command:

$ DEFINE PLI$COMPILER SYS$SYSTEM:PLIG.EXE

If it is desirable to make an older version of the compiler the default during a transition period while the new compiler is being evaluated, the system manager can place the command:

$ DEFINE/SYSTEM PLI$COMPILER SYS$SYSTEM:PLIG.EXE

in the system-wide startup file (SYS$MANAGER:SYSTARTUP_V5.COM). If individual users then want to use the version 3 compiler, they can issue the command

$ DEFINE PLI$COMPILER SYS$SYSTEM:PLI$COMPILER.EXE

4.5 KNOWN PROBLEMS AND RESTRICTIONS

• Compiler Bugcheck When Using /ANALYSIS_DATA In certain circumstances, the compiler will bugcheck when using /ANALYSIS_DATA to compile a program containing a compound assigment statement (an assignment statement with more than one item on the left side of the equal sign). An example is given below. The workaround for this problem is to rewrite the statement as two separate assignment statements.

  dcl 1 TEST_STRUCT static, 2 C char(50); dcl A fixed bin(15) static, 1 STRUCT based, 5 SUB, 10 ARRAY(A) like TEST_STRUCT; TEST: procedure; dcl P ptr, (LEN, I, J) fixed bin(31); I, J = LEN + size(P->STRUCT.SUB); end TEST;

• CHARACTER(*) Stack Usage Temporary stack space allocated for return values from routines returning CHARACTER(*) is not deallocated properly. The problem has to do with determining the lifetime of the temporary value. A sample code segment displaying this problem follows:

  DO I = 1 TO 1000; CHARACTER_STRING = ROUTINE_RETURNING_CHAR_STAR(); END;

  In this situation, the temporary storage for the return value is never deallocated, resulting in very considerable stack use. A work-around for this problem is to enclose the use of the routine in a BEGIN block. For example:

  DO I = 1 TO 1000; BEGIN; CHARACTER_STRING = ROUTINE_RETURNING_CHAR_STAR(); END; END;

  While this method is slightly more CPU-intensive because of the extra CALLS/RET sequence, it causes the stack top to be correctly reset between each iteration of the loop.

• Environment Option FILE_ID_TO This option is supported only for temporary files. In addition, the option does not work if the default directory is a rooted directory specification. This behavior will not be changed due to the low level of use. If this restriction is really a problem for you, please submit an SPR.
• AST-Level I/O Operations on a single PL/I file from both AST level and non-AST level are not permitted. Operations can be performed on a file at AST level; the restriction is that the operations cannot be mixed from both levels.
• Nonlocal GOTOs from AST Level to Non-AST Level A nonlocal GOTO from an AST routine to a label in a routine not invoked by the AST is not supported. If an attempt is made to perform a nonlocal GOTO in this fashion, AST level will not be cleared, and the program will typically fail the next time that RMS I/O is attempted. There are no plans to change this behavior, given that very few, if any, of the components on VMS are designed to allow arbitrary asynchronous unwinds through them.
• Silent Underflow During Compilation The compiler will silently replace an underflowing floating point constant with 0.0 during compilations.
• Descriptors for Picture Variables Picture variables are always passed (incorrectly) by class NRO descriptors regardless of the format of the picture variable. This problem will be addressed in a future maintenance release of VAX PL/I.
• When both the SELECT and WHEN clauses of a SELECT statement contain a substring expression, local memory for the first substring may be overwritten by the second substring. The workaround is to set up a variable to hold the substring expression for the WHEN and/or SELECT clauses. That is, either, but not both, the SELECT and WHEN clauses of a SELECT statement may contain a substring expression. This example shows code that gives an incorrect answer ('1' instead of '2'):

  txt = 'NUM'; n_chars = 2; SELECT (SUBSTR (txt, 1, n_chars)); WHEN (SUBSTR ('LOG', 1, n_chars)) option = 1; WHEN (SUBSTR ('NUMBER', 1, n_chars)) option = 2; OTHERWISE option = 0; END;

  The following example produces the correct answer ('2'):

  txt = 'NUM'; n_chars = 2; temp = SUBSTR (txt, 1, n_chars); SELECT (temp); WHEN (SUBSTR ('LOG', 1, n_chars)) option = 1; WHEN (SUBSTR ('NUMBER', 1, n_chars)) option = 2; OTHERWISE option = 0; END;

• The compiler can now handle records up to 32K which is RMS max. After a file is opened, a buffer equal to the longest record length is allocated. This buffer is then used when the record is read.
  This change is highly dependent on obtaining the longest record length value for a file from RMS (using the xab$w_lrl field of fhc_xab block) when the file is opened. However, there are some rare cases in which RMS fails to provide a correct value in that field. If this occures the %PLIG-F-READERR message, followed by an -RMS-F-USZ, invalid user buffer size error will be returned.
  One suggested user action is to edit the source file and write out a new version, causing RMS to update the lrl value in the file header.
• The compiler issues the error LOCNEED when the SIZE function references a based variable declared without an associated pointer. For example:

  TEST: PROC OPTIONS (MAIN); DCL 1 RECORD BASED, 3 ITEM1 CHAR(10), 3 ITEM2 CHAR(20); PUT EDIT (SIZE(RECORD)) (F(5)); /* %PLI-E-LOCNEED */ END;

• Please note that the descriptions provided in the PLI$STARLET, reflect the most common use, according to the VMS view, for that element. There may be some cases where we have described an element to be uses as a %ref, while you plan to use it as a %val. In some modules this may be a common problem. These entries cannot be defined both ways, and in some cases these definitions may need be modified by the user.

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