Resolving external references

You can request that the binder automatically search libraries to resolve external references that were not resolved during primary and secondary input processing. The binder can also process unresolved external references found in modules from additional data sources.

Note: The following discussion of automatic library call services does not apply to unresolved weak external references. They are left unresolved unless resolved to external symbols defined by modules included in the process of resolving other external references.

There are three ways to obtain automatic library call:

By providing AUTOCALL control statements. This is called incremental autocall and is processed at the time the control statement is encountered, using a source specified on the statement.
By providing LIBRARY control statements which specify sources to resolve references. Processing for these statements is deferred until all primary and secondary input sources have been exhausted.
By default if unresolved references remain at the end of the processing. The SYSLIB DD is used for this autocall.

There are also two ways to suppress automatic library call processing:

By providing an NCAL (or NOCALL) invocation option. This suppresses all automatic library call processing.
By providing LIBRARY control statements which specify names of external references that should not be resolved by automatic library call.

When you have requested automatic library call, the binder searches the directory of the automatic call library for an entry that matches the unresolved external reference. When a match is found, the entire member is processed as input to the binder.

Automatic library call can resolve an external reference when:

The external reference is a member name or an alias of a module in the call library, AND
The external reference is defined as an external name in the external symbol dictionary of a module contained in that member.

If an unresolved external reference is a member name or an alias in the library, but is not an external name in that member, the member is processed but the external reference remains unresolved unless it is subsequently defined.

When resolving external references, the binder searches the call library defined on the SYSLIB DD statement. The call library can contain program objects, load modules, or object modules and control statements (except INCLUDE, LIBRARY, and NAME).

Modules from libraries other than the SYSLIB call library can be searched by the binder as directed by the LIBRARY control statement. The library specified in the control statement is searched for member names that match specific external references that are unresolved at the end of input processing. If any unresolved references are found in the modules located by automatic library call, they are resolved by another search of the library. Any external references not specified on a LIBRARY control statement are resolved from the library defined on the SYSLIB DD statement.

To prevent the binder from automatically searching call libraries, use either the LIBRARY statement for selected unresolved external references, or the NCAL option on the EXEC statement for all unresolved external references. See Directing external references to a specific library for a discussion of the LIBRARY control statement and the NCAL option.

Attribute mismatches: At the end of input processing, the binder will diagnose mismatches in the XPLINK attribute, 64-bit addressing mode, and the signature fields between caller and callee. A mismatch is indicated by a severity code 8 error message.