Error: Failed to build dvisvgm: command execution failed

[dbl001 (dbl)]

:info:build AttributeExtractor.cpp:116:24: error: constexpr variable 'names' must be initialized by a constant expression

I'm getting the following error building: dvisvgm

$ sudo port upgrade outdated
Password:
--->  Computing dependencies for dvisvgm
--->  Building dvisvgm
Error: Failed to build dvisvgm: command execution failed
Error: See /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_graphics_dvisvgm/dvisvgm/main.log for details.
Error: Follow https://guide.macports.org/#project.tickets to report a bug.

[michaelld (Michael Dickens)]

Hmm ... looks like although it's checking for c++11, it really requires c++14. Let me see about patching it & restricting compilers to one that's c++14 compliant ...

[Ionic (Mihai Moldovan)]

Forcing macports-clang-6.0 worked for me.

Note that make_array is an experimental feature - not part of either C++11, 14, or even 17. It's scheduled for maybe-inclusion in C++20, but no guarantees.

It was ​implemented in clang in Oct 2017, past the release of clang-5.0 (~Sep 2017). The first version to have proper support for it is thus 6.0.

Since the C++11 1.1 PG already forces mp-clang-5.0 via compiler.whitelist (which is really a compiler.force operation...), using compiler.whitelist macports-clang-6.0 in dvisvgm should be enough to get this fixed across the board.

[Ionic (Mihai Moldovan)]

Err, actually, that only holds for systems using libc++ and are not too old.

We'd really have to reimplement the cxx11-1.1 PG in dvisvgm, because we naturally want to keep ppc machines on gcc-6 of course.

So rather something like

if {${configure.cxx_stdlib} eq "libstdc++"} {
  if {(${os.platform} ne "darwin" || ${os.major} >= 10) && ${build_arch} ne "ppc" && ${build_arch} ne "ppc64"} {
    compiler.whitelist macports-clang-6.0
  }
} else {
  compiler.fallback-append macports-clang-6.0
  compiler.blacklist-append {clang < 600} macports-clang-3.* macports-clang-4.0 macports-clang-5.0
}

[mgieseki (Martin Gieseking)]

Replying to Ionic:

Note that make_array is an experimental feature - not part of either C++11, 14, or even 17. It's scheduled for maybe-inclusion in C++20, but no guarantees.

I stumbled over this ticket about the build issue. Just for clarification: dvisvgm does not use std::make_array but provides its own implementation util::make_array defined in utils.hpp. The sources build fine for me on Linux even with GCC 4.8.

[Ionic (Mihai Moldovan)]

Okay, so my analysis was wrong, but it must still be using a feature (no idea which one) only available in clang-6.0+ and not older versions.

[Ionic (Mihai Moldovan)]

Turns out michaelld was probably right - std::forward is constexpr since C++14, which is needed here. Not sure why that code would compile in C++11 mode even with newer clang versions (or, for that matter, g++), since it should be non-constexpr in C++11 mode.

Edit: probably because marking something constexpr has no negative side-effects, so it doesn't have to done conditionally. That's just a guess, though.

[mgieseki (Martin Gieseking)]

std::forward is indeed a problem. I'll drop the make_array stuff in the next release of dvisvgm. If you like, you can already apply attachment:make_array.patch​ to fix the build issue.

[michaelld (Michael Dickens)]

Thanks; will do shortly.

[michaelld (Michael Dickens)]

In 385eb361f7436ed9685832c59ed140e28c56e264/macports-ports (master):

dvisvgm: add patch from upstream to fix changed liquid-dsp API usage

rev-bump just in case

Closes: #58347

[michaelld (Michael Dickens)]

Done! Thank you @mgieseki for the quick fixing of this issue!