(This question is a bit obscure without a lot of motivation so please bear with me.)
For the sake of discussion let's assume I have two files, a.cpp and b.hpp. Suppose a.cpp has the declaration
template <typename T> void foo(T& t);
and somewhere in the code it has the commands:
foo<int>(1234);
foo<double>(12.34);
while b.hpp holds the actual (templated) definition and nothing else.
Now, a.cpp, compiled without including b.hpp will compile into an object file, a.o, which is expecting to be linked with other files containing the object code for foo<int> and foo<double>. In itself, b.hpp makes no instantiations of foo(), so it's useless to compile it alone.
However, if I were to determine which instantiations are necessary, and generate a.aux.cpp containing minimal code to instantiate exactly those templates needed for a.cpp, I would not have to manually ensure the instantiations are made.
So, how do I go about achieving this? I was thinking along the lines of doing
nm --undefined-only a.cpp | sed 's/^ *//;' | c++filt | grep foo
to get the signatures. Then I need to force their instantiation without actually causing any other side-effects... perhaps define a variable whose type is a pointer to foo<T> for each value of T I find.
Anyway, this all seems very kludgy and I was wondering whether some build-related tools do this for you. Or whether I should have another approach altogether.
