Matthew Knepley <[email protected]> writes:

On Sun, Dec 31, 2017 at 2:35 PM, Jed Brown <[email protected]> wrote:

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Matthew Knepley <[email protected]> writes:

...

On Sun, Dec 31, 2017 at 1:55 PM, Jed Brown <[email protected]> wrote:

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These look like linker errors and that build uses --with-cxxlib-autodetect=0. We either need a rule to *link* C++ using CXX (i.e., mpicxx) or add LIBS=-lstdc++.

I thought we were doing this (linking C++ mains with CXX).

After compiling to the object file (ex3.o) we don't know what language main was written in, and this doesn't solve the actual problem that C++ linking is required if any object (not just main) depends on C++.

My thinking here was the following:

1) No C++ is allowed in PETSc, unless --with-clanguage=cxx, in which case the linker is C++ 2) If C++ is in an external library, then that configure requires the C++ library 3) The executable itself could be C++, in which case I proposed using the C++ linker explicitly

About not knowing which objects come with C++ main: I thought we did. Don't they go into a separate set?

Right, we do have that information for tests. Note that a single test executable can depend on multiple source files, and the one containing main might not be C++ while another is. I don't know if there are any such instances in PETSc. I can change the build rules for tests with C++ sources later today.