[geezerjay]

> It is ridiculous that header-only is considered an advantage.

Why do you believe it's ridiculous? Being able to integrate a third-party library by just adding a few source files to your source tree is as simple as it gets.

> The state of C++ build tools is very poor, and it is harming the language as a whole.

This assertion makes no sense, particularly in the light of this discussion. Installing a headers-only library is a solved problem, and even template-heavy libraries such as Eigen are already distributed and installed quite easily with standard linux package managers.

[rienbdj]

I should clarify. Being able to add headers to a project in C++ is easy but adding translation units is not (usually). This encourages header-only libraries even when they are not really appropriate, increasing compilation times etc.

[comex]

Other things that become a huge albatross and are thus avoided:

- Adding compile-time build steps, e.g. for code generation.

- Adding dependencies of your own, even on, say, a tiny library of helper functions – unless you want to copy and paste it into your header.

With a package manager, those things 'just work'. Package managers also make it much easier to update to newer versions of the library as they're released.

[geezerjay]

I don't see your point. Adding custom build steps is a basic feature that's supported by pretty much every single popular build system for decades now, just like adding your own dependencies. Heck, cmake even allows users to configure a project to download packages from the web and integrate them in a build and with custom build steps if needed. Even if we ignore this fact, there are also package management tools such as Conan which handle this case quite nicely and also support cross-platform deployments.

And let's not pretend that in some platforms such as pretty much each and every single popular linux distro already package and distribute C++ libraries and offer packaging tools and also package repository services to distribute any dependency.

I'm starting to suspet that those who complain about these sort of issues have little to no experience with C++.

[comex]

> [cmake stuff]

If that were sufficient, we wouldn't see so many header-only libraries.

> Even if we ignore this fact, there are also package management tools such as Conan which handle thjs case quite nicely and also supporting cross-platform deployments.

Conan would be a decent solution if everyone used it. I tried it briefly last year; I ended up not using it for that project because it didn't support certain features I wanted (namely, compiler toolchain management), plus Bintray was having issues at the time. But my overall impression was that it was... fine. I may end up using it in the future.

For now, though, as a library author, most of your users won't have Conan set up; as a library consumer, most of the libraries you use won't be on Conan; and in either position, most people building your software won't know how to use Conan. Until that changes, it doesn't really solve the library friction problem.

> And let's not pretend that in some platforms such as pretty much each and every single popular linux distro already package and distribute C++ libraries and offer packaging tools and also package repository services to distribute any dependency.

If you have a library which is popular or a dependency for something that's popular, then yes, the N different Linux distributions and package managers for other operating systems will all handle packaging your library themselves. If you just want to be able to upload some code and have it be immediately reusable by the wider world, well, it's not particularly feasible to make packages for N different distributions yourself, and even if you do, the Linux distros most people use are months to years behind the bleeding edge of software releases, so you'll have a while to wait before those packages actually reach people.

[_pmf_]

Sometimes I wonder why projects are either "single header only" or tens to hundreds of separate modules. One header and one source module would be a nice compromise regarding compile time vs. ease of use.

Yes, I realize that some header only libraries support using the header as either header or implementation, but this still blows up compile time.

[BubRoss]

Does it really blow up compile time? Translation units and optimization are usually where compile time is spent. Having fewer but fatter translation units helps compile times tremendously while most of the time per translation unit is spent in stages beyond the source compiling in LLVM.

Boost is really the only example I can think of where small utility comes at the expense of huge compile time increases.

[mehrdadn]

Header-only libraries aren't generally single-header-only. That's a bit of an extreme.

[geezerjay]

> I should clarify. Being able to add headers to a project in C++ is easy but adding translation units is not (usually).

Where do you see a difference?

>This encourages header-only libraries even when they are not really appropriate, increasing compilation times etc.

Thus assertion makes no sense. Headers only declare interfaces, and you only require headers-only libraries if you're deep in template and template metaprogramming land. Evenso it's quite trivial to package and distribute those libraries just like any other library