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stop recommending -fexternal-templates

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From-SVN: r55713
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Jason Merrill 2002-07-24 12:23:14 -04:00
parent 7e51e626ab
commit 979b1d1834
1 changed files with 0 additions and 35 deletions
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gcc/doc/extend.texi
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@ -7164,41 +7164,6 @@ each translation unit will contain instances of each of the templates it
uses. In a large program, this can lead to an unacceptable amount of code
duplication.
@item
@opindex fexternal-templates
Add @samp{#pragma interface} to all files containing template
definitions. For each of these files, add @samp{#pragma implementation
"@var{filename}"} to the top of some @samp{.C} file which
@samp{#include}s it. Then compile everything with
@option{-fexternal-templates}. The templates will then only be expanded
in the translation unit which implements them (i.e.@: has a @samp{#pragma
implementation} line for the file where they live); all other files will
use external references. If you're lucky, everything should work
properly. If you get undefined symbol errors, you need to make sure
that each template instance which is used in the program is used in the
file which implements that template. If you don't have any use for a
particular instance in that file, you can just instantiate it
explicitly, using the syntax from the latest C++ working paper:
@example
template class A<int>;
template ostream& operator << (ostream&, const A<int>&);
@end example
This strategy will work with code written for either model. If you are
using code written for the Cfront model, the file containing a class
template and the file containing its member templates should be
implemented in the same translation unit.
@item
@opindex falt-external-templates
A slight variation on this approach is to use the flag
@option{-falt-external-templates} instead. This flag causes template
instances to be emitted in the translation unit that implements the
header where they are first instantiated, rather than the one which
implements the file where the templates are defined. This header must
be the same in all translation units, or things are likely to break.
@xref{C++ Interface,,Declarations and Definitions in One Header}, for
more discussion of these pragmas.
@end enumerate