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Order Number: AA--PUNZJ--TK
This guide describes using the Compaq C compiler on OpenVMS systems. It contains information on Compaq C program development in the OpenVMS environment, Compaq C features specific to OpenVMS systems, and cross-system portability concerns.
Revision/Update Information:
This revised guide supersedes the
DEC C User's Guide for OpenVMS Systems (Order No.
AA--PUNZH--TK)
Software Version: Compaq C Version 6.2 for OpenVMS Systems
Compaq Computer Corporation
Houston, Texas
Digital Equipment Corporation makes no representations that the use of its products in the manner described in this publication will not infringe on existing or future patent rights, nor do the descriptions contained in this publication imply the granting of licenses to make, use, or sell equipment or software in accordance with the description.
Possession, use, or copying of the software described in this publication is authorized only pursuant to a valid written license from Digital or an authorized sublicensor.
Compaq, the Compaq logo, Alpha, DEC, DECnet, DECtalk, DECthreads, DIGITAL, OpenVMS, RMS, Tru64 UNIX, VAX, VAX C, CDD/Repository, VMS, and the DIGITAL logo are registered in the U.S. Patent and Trademark Office.
The following are third-party trademarks:
Microsoft is a registered trademark and Visual C++ is a trademark of Microsoft Corporation.
UNIX is a registered trademark in the United States and other countries licensed exclusively through X/Open Company Ltd.
IEEE is a registered trademark of the Institute of Electrical and Electronics Engineers, Inc.
This document is available on CD-ROM.
This document was prepared using VAX DOCUMENT, Version V3.2-1m.
| Contents | Index |
This guide contains the information necessary for developing and debugging Compaq C (formerly DEC C) programs on the OpenVMS operating system. Compaq C is compliant with the International Standards Organization (ISO) C Standard (ISO 9899:1990[1992]), formerly the American National Standard for Information (ANSI) Systems-Programming Language C (document number: X3.159-1989), called the ANSI C Standard in this guide. Compaq C is an ANSI compliant C compiler for the OpenVMS operating system on VAX and Alpha processors and for the Tru64 UNIX® operating system on Alpha processors. Through use of command-line options, Compaq C is compatible with older dialects of C, including common usage C and VAX C.
This guide also includes Compaq C language features specific to OpenVMS systems, as well as information about porting C programs to and from OpenVMS and other operating systems. For more information about porting programs to and from other operating systems, see the Compaq C Run-Time Library Reference Manual for OpenVMS Systems.
You may send comments or suggestions regarding this guide or any Compaq C document by sending electronic mail to the following Internet address:
c_docs@zko.dec.com
This guide is intended for experienced programmers who need to develop Compaq C programs on OpenVMS systems, for users who need to know the difference between Compaq C and other implementations, and for experienced C users who need to reference language information specific to OpenVMS systems. You should be familiar with one high-level language and should have some familiarity with the DIGITAL Command Language (DCL). If you are not familiar with or need to reference information about the DCL, see Chapter 1.
This guide has the following chapters and appendixes:
You may find the following documents useful when programming in Compaq C:
1 Brian W. Kernighan and Dennis M. Ritchie, The C Programming Language, Second Edition (Englewood Cliffs, New Jersey: Prentice Hall, 1988). |
Table 1 lists the conventions used in this guide.
| Convention | Meaning |
|---|---|
| [Return] | The symbol [Return] represents a single stroke of the Return key on a terminal. |
| Ctrl/X | The symbol Ctrl/X, where the letter X represents a terminal control character, is generated by holding down the Ctrl key while pressing the key of the specified terminal character. |
|
switch
statement
fprintf function auto storage class |
In syntax definitions, items appearing in monospaced type identify language keywords and the names of OpenVMS and Compaq C Run-Time Library functions. |
| arg1 | Italic type indicates a placeholder, such as an argument or parameter name, and the introduction of new terms. |
| $ run cprog [return] | Interactive examples show user input in boldface type. |
|
float x;
. . . x = 5; |
A vertical ellipsis indicates that not all of the text of a program or program output is illustrated. Only relevant material is shown in the example. |
| option,... | A horizontal ellipsis indicates that additional parameters, options, or values can be entered. A comma that precedes the ellipsis indicates that successive items must be separated by commas. |
| [output-source,...] | Square brackets, in function synopses and a few other contexts, indicate that a syntactic element is optional. Square brackets are not optional, however, when used to delimit a directory name in an OpenVMS file specification or when used to delimit the dimensions of an array in Compaq C source code. |
|
sc-specifier ::=
auto static [extern] register |
In syntax definitions, items appearing on separate lines are mutually exclusive alternatives. |
| {a|b} | Braces surrounding two or more items separated by a vertical bar (|) indicate a choice; you must choose one of the two syntactic elements. |
| <ucDelta symbol> | A delta symbol is used in some contexts to indicate a single ASCII space character. |
A platform is a combination of operating system and hardware that provides a distinct environment. This guide contains information applicable to the OpenVMS operating system on both the VAX and Alpha architectures.
The information in this guide applies to both of these platforms, except when specifically labeled, as follows:
| Label | Explanation |
|---|---|
| (ALPHA ONLY) | Specific to an Alpha processor running the OpenVMS operating system. |
| (VAX ONLY) | Specific to a VAX processor running the OpenVMS operating system. |
Compaq C Version 6.2 primarily contains a number of new language features from the in-process revision to the C standard, C9X (expected to be C99), and from the gcc compiler (to aid compatibility with source code from Linux systems). It also has run-time performance enhancements (including tuning for the EV6 processor and per-function optimization controls) and diagnostic message improvements, as well as bug fixes and miscellaneous improvements.
The following specific enhancements have been made in this version:
#pragma message (quoted-string) |
file:/sys$common/syshlp/cc$alpha_help_062/index.htm (ALPHA ONLY) file:/sys$common/syshlp/cc$vax_help_062/index.htm (VAX ONLY) |
See the Compaq C release notes for a comprehensive list of enhancements and fixes.
See Appendix A for a summary of features that distinguish Compaq C for OpenVMS Systems from VAX C Version 3.2.
This chapter describes the following information about developing Compaq C programs on an OpenVMS system:
This section provides a brief overview of the DCL commands used for program development. The following sections provide more detailed information about these topics.
Figure 1-1 shows the basic steps in Compaq C program development.
Figure 1-1 DCL Commands for Developing Programs
To create a Compaq C source program at DCL level, you must invoke a text editor. In Figure 1-1, the EDIT command invokes the default editor EDT to create the source program AVERAGE.C. You can use another editor, such as the OpenVMS Text Processing Utility (TPU) or the Compaq Language-Sensitive Editor (LSE). (LSE is a product that must be purchased separately; see Appendix C for more information.) A file type of C is used to indicate that you are creating a Compaq C source program. C is the conventional file type for all Compaq C source programs.
When you compile your program with the CC command, you do not have to specify the file type; by default, Compaq C searches for files with a file type of C.
If your source program compiles successfully, the Compaq C compiler creates an object file with the file type OBJ.
However, if the Compaq C compiler detects errors in your source program, the system displays each error on your screen and then displays the DCL prompt. You can then reinvoke your text editor to correct each error.
You can specify command qualifiers on the CC command. Command qualifiers cause the Compaq C compiler to perform additional actions. In the following example, the /LIST qualifier causes the Compaq C compiler to produce the listing file AVERAGE.LIS:
$ CC/LIST AVERAGE |
For a complete description of all CC command qualifiers, see Section 1.3.4.
After your program has compiled successfully, invoke the OpenVMS Linker to create an executable image file. For example:
$ LINK AVERAGE |
The linker uses the object file produced by Compaq C as input to produce an executable image file as output. (The executable image is a file containing program code that can be run on the system.)
You can specify command qualifiers with the DCL command LINK. For a complete list and explanation of all the command qualifiers available with the LINK command, see Section 1.4.2.
After producing the executable image file, use the RUN command to
execute your program.
1.2 Creating a Compaq C Program
To create and modify a Compaq C program, you must invoke a text
editor. The OpenVMS system provides you with two text editors:
EDT and the OpenVMS Text Processing Utility (TPU). The
following section discusses TPU. See the OpenVMS EDT Reference Manual for more
information on EDT.
1.2.1 Using TPU
TPU is a high-performance, programmable utility. It provides two editing interfaces: the Extensible VAX Editor (EVE), described in the following section, and the TPU EDT Keypad Emulator. You can also create your own interfaces.
Like EDT, TPU provides you with an online help facility that you can access during your editing session. When you invoke TPU to create a file, a journal file is automatically created. You can use this journal file to recover your edits if the system fails during an editing session. To recover your edits, enter the EVE/RECOVER command.
Unlike EDT, TPU provides multiple windows. This feature allows you to
view two files on your screen at the same time.
1.2.2 The EVE Interface to TPU
EVE is an interactive text editor that allows you to execute common editing functions using the EVE keypad or to execute more advanced functions by entering commands on the EVE command line. The following command line invokes the EVE editor and creates the file PROG_1.C:
$ EDIT/TPU PROG_1.C |
You can define a global symbol for the EDIT/TPU command by placing a symbol definition in your LOGIN.COM file. For example:
$ EVE == "EDIT/TPU" |
After this command line is executed, you can type EVE at the DCL prompt followed by the name of the file you want to modify or create.
For more information on using EVE, see the Guide to VMS Text Processing.
1.3 Compiling a Compaq C Program
The Compaq C compiler performs the following functions:
The following sections discuss the CC command and its qualifiers.
1.3.1 The CC Command
To invoke the Compaq C compiler, enter the CC command at the DCL prompt ($). The CC command has the following format:
|
CC[/qualifier...][ file-spec [/qualifier...]],... |
This note applies to OpenVMS VAX systems that have both Compaq C and VAX C installed. The CC command is used to invoke either the VAX C or Compaq C compiler. If the Compaq C installation procedure detects that your system already has a VAX C compiler installed on it, the installer is given the option to specify which compiler gets invoked by default whenever the CC command verb is used. To invoke the compiler that is not the default, use the CC command with the appropriate qualifier: CC/DECC for the Compaq C compiler, or CC/VAXC for the VAX C compiler. Where the CC command appears in examples in this manual, CC/DECC is assumed to be the default. |
/qualifier
An action to be performed by the compiler on all files or specific files listed. When a qualifier appears directly after the CC command, it affects all the files listed. When a qualifier appears after a file specification, it affects only the file that immediately precedes it. However, when files are concatenated, these rules do not apply.file-spec
An input source file that contains the program or module to be compiled. You are not required to specify a file type if you give your file a .C file extension; the Compaq C compiler adopts the default file type C.
You can include more than one file specification on the same command line by separating the file specifications with either a comma (,) or a plus sign (+). If you separate the file specifications with commas, you can control which source files are affected by each qualifier. In the following example, the Compaq C compiler creates an object file for each source file but creates only a listing file for the source files PROG_1 and PROG_3:
$ CC /LIST PROG_1, PROG_2/NOLIST, PROG_3 |
If you separate file specifications with plus signs, the Compaq C compiler concatenates each of the specified source files and creates one object file and one listing file. In the following example, only one object file is created, PROG_1.OBJ, and only one listing file is created, PROG_1.LIS. Both of these files are named after the first source file in the list, but contain all three modules.
$ CC PROG_1 + PROG_2/LIST + PROG_3 |
Any qualifiers specified for a single file within a list of files separated with plus signs affect all the files in the list. See the description of the /PLUS_LIST_OPTIMIZE qualifier for its affect on file concatenation.
Concatenating source files without using the /PLUS_LIST_OPTIMIZE qualifier (ALPHA ONLY) is not recommended because potential conflicts in the name space of declared objects can result in compilation errors or incorrect run-time behavior. |
A more common use of plus-list concatenation is for specifying text libraries. You can specify the name of a text library on the CC command line to compile a source program. A text library is a file that contains text organized into modules indexed by a table. Text libraries have a .TLB default file extension. In the following example, text libraries A.TLB and B.TLB are made available for searching for text library modules during the compilation of source file TEST.C:
$ CC TEST.C + A.TLB/LIB + B.TLB/LIB |
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