1.1 Using the DEC C Run-Time Library

When working with the DEC C RTL, you must be aware of some implementation specifics.

First, if you plan to use DEC C RTL functions in your C programs, make sure that a function named main or a function that uses the main_program option exists in your program. For more information, see the DEC C Language Reference Manual or the DEC C User's Guide for OpenVMS Systems.

Second, the DEC C RTL functions are executed at run time, but references to these functions are resolved at link time. When you link your program, the OpenVMS Linker resolves all references to DEC C RTL functions by searching any shareable code libraries or object code libraries specified on the LINK command line.

You can use the DEC C RTL as a shareable image or you can use the DEC C RTL object libraries.

When you use the DEC C RTL as a shareable image, the code for the RTL resides in an image file in SYS$SHARE and is shared by all DEC C programs. After execution, control returns to your program. This process has a number of advantages:

• You reduce the size of a program's executable image.

• The program's image takes up less disk space.

• The program swaps in and out of memory faster due to decreased size.

• With DEC C and DEC C++, you no longer need to define an options file when linking your program against the shareable image. Linking against the RTL shareable image is now much simpler than it was with VAX C. In fact, it is the default method of linking to the DEC C RTL.

When linking to the DEC C RTL, you do not need to define any LNK$LIBRARY logicals. In fact, you should deassign LNK$LIBRARY because linking with the shareable image is more convenient than linking with the DEC C RTL object libraries.

See your OpenVMS, DEC C, or DEC C++ release notes for any supplemental information about linking with the DEC C RTL.