c++11 ABI on gcc versions > 5.1

[ericmehl]

After updating my Linux build chain to the latest 2.1.1 release (both downloaded from the release page and building it from source) and therefore c++14 in efcc69c, my locally built Cortex and Gaffer no longer run. I'm building from master with gcc 7.5 (presumably anything over 5.1 would fail based on the next paragraphs).

I get unresolved external symbols due to building Boost (and perhaps others, but Boost was the first library loaded that caused the error) in c++14 without the _GLIBCXX_USE_CXX11_ABI=0 macro set. It is set in Cortex and Gaffer so they were looking for symbols without the __cxx11 namespace and not finding them.

Commenting those lines out of Cortex and Gaffer builds sorted it for me Gaffer runs as expected (and tests succeed as well).

Is this something I should do a PR for to remove the _GLIBCXX_USE_CXX11_ABI=0 lines in Cortex and Gaffer Scons? I don't think that would cause problems in pre-5.1 gcc, but not sure if that would run afoul of other solutions IE or others have made.

[andrewkaufman]

It's intentional to have those, its specified in the VFX Platform. I believe boost, etc should all have been built with that set as well. We don't use the dependencies project (releases or build scripts) at IE, but I'm not sure why this that hasn't come up in practice for others...

[ericmehl]

Ah, I see now. So maybe I need to add the _GLIBCXX_USE_CXX11_ABI=0 to Boost and maybe TBB since that was changed in the same commit.

Yes, strange that it hasn't come up elsewhere yet. The CI builds use a pre-5.1 gcc so maybe others haven't hit it yet.

I'll look into it more next week.

[johnhaddon]

We (GafferHQ and IE) both build on Centos 7, where the compilers have been built to default to _GLIBCXX_USE_CXX11_ABI=0. Other distros have chosen otherwise, so I suspect you're on a distro which defaults to 1. I'd be happy to accept a PR to add a CXX11_ABI boolean argument in the SConstruct, but I think it should default to 0 still.

[ericmehl]

Strange, it seems to be building fine for me again now after double checking that I am building from the GafferHQ dependencies. I must have gotten my builds mixed in with the release build which leading to the confusion..

I'm using Ubuntu 18.04 which I'm guessing does what John mentioned and sets _GLIBCXX_USE_CXX11_ABI=1 by default.

Anyhow, nothing to see here now, and I can continue to make sure my Windows dependency builds aren't breaking Linux.