HP eld Manual page 24

Introduction to eld
There are four types of TNS/E object file:
Type of Object File
Linkfile
Program
DLL
Import Library
Collectively, programs and DLLs are called loadfiles. Loadfiles and import libraries are
built by the linker.
The main distinctions occur between linkfiles and loadfiles. There is little difference
between a program and a DLL as far as the file format is concerned, and an import
library is a subset of what is in a DLL.
A loadfile may refer by name to symbols that exist in other loadfiles in the same
process. Such references are resolved when the loadfiles are brought into memory by
the runtime loader (rld) or by the C/C++ runtime procedure named dlopen(). When
the loadfile was originally built by the linker it is also possible that the linker tried to
resolve such references. A loadfile whose references have been resolved by the linker
is said to be preset.
A process can also use one user library. A user library is a DLL. Nothing within a user
library distinguishes it from other DLLs, and a DLL that serves as the user library for
one program can also be used like any other DLL by other programs. The only
difference between the user library and other DLLs is in the way the program identifies
the user library that it uses. For a DLL to be used as a user library at runtime its
filename must be in the Guardian name space.
An import library can take the place of a DLL at link time. One use of import libraries is
to save space. Another use is for security, when it is necessary for the linker to read
the header information but it is not desirable for others to be able to see the code.
Import libraries are further categorized as complete or incomplete. The difference is
that an incomplete import library need not contain the correct addresses for symbols. A
complete import library can be used by the linker when presetting a loadfile. The linker
can use an incomplete import library to check for unresolved references, but not to
preset.
DLLs and import libraries can also be used at compile time by the COBOL compiler to
find out information about procedure call interfaces.
Description
Object files that are produced by a compiler or by the
assembler that can be given as input to the linker. It is also
possible for the linker to produce a linkfile as output when
run with the -r option.
This is the main program. There is one program in every
process.
This is a dynamic-link library. It is an object file that is not a
program but can also be part of a process. A process can
contain any number of DLLs. DLLs are also used by the
linker when building other programs or DLLs.
This is a file that contains just part of a DLL that is needed
at link time to build other DLLs or programs.
eld Manual—527255-009
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Native Object Files