HP aC++/HP C A.06.28 Programmer's Guide Integrity servers (769150-001, March 2014)

Why Use Compile-Time Instantiation
Compile-time instantiation is the default. It is easy to use. Your code may compile faster when using
compile-time instantiation.
If your development environment uses a version control system that is sensitive to file modifications,
you may want to use the current default, compile-time instantiation, to avoid major code rebuilds.
NOTE: If you have used automatic instantiation with earlier versions of HP aC++ there may be
some migration issues. See “Migrating from Automatic Instantiation to Compile-time Instantiation”
(page 135) for more information.
Scope
If your source code contains templates and you do not specify any template command-line options
nor explicit instantiations, compile-time instantiation takes place for any use of a template. If you
specify a template command-line option, the option takes precedence for all translation units on
the command line. Any explicit instantiation takes precedence over either a command-line option
or compile-time instantiation.
Usage
Compared with developer-directed instantiation, compile-time instantiation involves less coding
time for the developer. However, the design of your application may require the use of some form
of directed instantiation.
Migrating from Automatic Instantiation to Compile-time Instantiation
If you have used automatic instantiation with earlier versions of HP aC++ there will be some known
migration problems. The following migration problems may occur:
• Creating object files
• Creating an executable
• Closing a set of object files prior to creating a library (.a or .so)
• Creating a shared library (.so)
The following sections describe specific migration scenarios and illustrate possible migration
problems and solutions:
Possible Duplicate Symbols in Shared Libraries
An existing compiler defect may be more apparent, if in HP aC++ A.02.00 or A.01.04 and prior
versions you built a shared library using automatic instantiation (the prior default using the assigner)
and now build that library using the current default (compile-time) instantiation. The defect relates
to template objects with constructors or other runtime initializers that have been globally defined
in more than one shared library on the link line. If such an object is defined in n shared libraries,
it will be initialized and destructed n times at runtime.
When building the same application with the current default, the libraries are not closed prior to
the final link, and the likelihood of a template symbol being defined in more than one shared
library will increase.
Possible Duplicate Symbols in Archive Libraries
If you have built an archive library using automatic instantiation in HP aC++ A.02.00 or A.01.04
and prior versions, and you rebuild that library using the current (compile-time) instantiation, it is
possible that duplicate symbol problems not apparent in the prior release will generate errors in
the current release.
This is because the current default uses the linker, rather than the assigner, to determine which
object file to pick to satisfy instantiation requests.
Invoking Compile-Time Instantiation 135