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C and C++ Implementation Details
Note
In C, this code is legal but has a different meaning. A tentative declaration of f is
followed by its definition.
5.2.5 Template instantiation
The ARM compiler does all template instantiations automatically, and makes sure there
is only one definition of each template entity left after linking. The compiler does this
by emitting template entities in named common sections. Therefore, all duplicate
common sections, that is, common sections with the same name, are eliminated by the
linker.
Note
You can limit the number of concurrent instantiations of a given template with the
--pending_instantiations compiler option.
See also --pending_instantiations=n on page 2-103 for more information.
Implicit inclusion
When implicit inclusion is enabled, the compiler assumes that if it requires a definition
to instantiate a template entity declared in a .h file it can implicitly include the
corresponding .cc file to get the source code for the definition. For example, if a
template entity ABC::f is declared in file xyz.h, and an instantiation of ABC::f is required
in a compilation but no definition of ABC::f appears in the source code processed by the
compilation, then the compiler checks to see if a file xyz.cc exists. If this file exists, the
compiler processes the file as if it were included at the end of the main source file.
To find the template definition file for a given template entity the compiler has to know
the full path name of the file where the template is declared and whether the file is
included using the system include syntax, for example, #include . This
information is not available for preprocessed source containing #line directives.
Consequently, the compiler does not attempt implicit inclusion for source code
containing #line directives.
The compiler looks for the definition-file suffixes .cc and .CC.
You can turn implicit inclusion mode on or off with the command-line options
--implicit_include and --no_implicit_include.
Implicit inclusions are only performed during the normal compilation of a file, that is,
when not using the -E command-line option.
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