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A problem of template implicit instantiation
- From: Yu Sheng Oh <humbleoh at gmail dot com>
- To: gcc-bugs <gcc-bugs at gcc dot gnu dot org>
- Date: Fri, 5 Dec 2014 10:20:15 +0800
- Subject: A problem of template implicit instantiation
- Authentication-results: sourceware.org; auth=none
HI,
I have a piece of code at "http://goo.gl/r2ySE6";
Refer to the code, with option of "-O2 -std=c++1y", when we comment
out the statement "id<int>;" clang-3.4.1 compiles the code
successfully, but g++-4.9.0 compiles failed, where g++ complains that
"unresolved overloaded function type", which in turn implies that at
the point of calling compose function, id<int> is not instantiated.
"3. Unless a function template specialization has been explicitly
instantiated or explicitly specialized, *the function template
specialization is implicitly instantiated when the specialization is
referenced in a context that requires a function definition to exist.*
"[temp.inst]
At the point of calling the compose function, the function definition
for id<int> is required, and so, id<int> should be implicitly
instantiated.
Based on my argument, it is a bug in g++-4.9.0, but I am not 100% sure
of it. Please advice.
PS: Yongwei Wu is credited for discovering the problem.