macports-gcc-7 is not selected on libstdc++ systems with compiler.cxx_standard 2017

[evanmiller (Evan Miller)]

 --->  Configuring webkit2-gtk
Failed to configure webkit2-gtk: Invalid value for configure.compiler:

It appears that the GCC7 installed on my system is not recognized as supporting C++17 (contrary to CompilerSelection). Manually setting the compiler

sudo port configure webkit2-gtk configure.compiler=macports-gcc-7

allows configuration to proceed.

[evanmiller (Evan Miller)]

Build log

[kencu (Ken)]

This error comes from MacPorts, and it seems to think you have set configure.compiler to ""

270     :error:configure Failed to configure webkit2-gtk: Invalid value for configure.compiler:
271	:debug:configure Error code: NONE

Can you clean and try again, in case you might have accidentally left a space around the "=" sign or something?

[kencu (Ken)]

oh, is this log coming from your first attempt, before you forced configure.compiler on the command line?

If so, that is weird. But not impossible. This pathway is not well travelled, and there could be hiccups in it.

configure.compiler, as chosen by base, should never be empty....but ....

[kencu (Ken)]

I was able to get webkit2-gtk working as far back as 10.6 with several days worth of efforts.

I can't recall just now if I ever got it working on 10.5 Intel.

It would be a very pleasant and unexpected surprise if it build on anything before that!

[evanmiller (Evan Miller)]

Yes, the error appears before forcing configure.compiler on the command line. FWIW I don't see this error with any other packages. But any command involving webkit2-gtk produces the warning:

Warning: All compilers are either blacklisted or unavailable; defaulting to first fallback option

[jmroot (Joshua Root)]

In 087ce29788c7ada01324163c2248ff05e49dd8f4/macports-base (master):

Fix values returned by portconfigure::get_min_gcc

These need to match the final segment of a configure.compiler value.
For example, macports-gcc-4.8 yields a version of 4.8, and
macports-gcc-7 yields 7. So 8.1 would not match macports-gcc-8 even
though the gcc8 port in fact provides a newer version than that. Also,
vercmp treats n.0 as greater than n, not equal.

Fixes: #63281