Issues with building on linux

[Elefant-Freeciv]

When building on Linux, i ran into a few problems.

1. error: explicit qualification in declaration of
   This error popped up several times throughout the build.
   Affected files: CommonShared.cpp, CvGameCoreUtils.cpp, CvString.cpp, AppUIUtil.cpp, CivIni.cpp, CommandLine.cpp,
   Common.cpp, CvVFS.cpp, DXT.cpp, IniReader.cpp
   To fix, remove all instances of " ::" with " " and "(::" with "(".

2. collect2: fatal error: cannot find 'ld'
   This can be solved by installing the mold linker. lld and others don't work.

3. mold: fatal: cannot open HeckTUIInputTest: Is a directory
   collect2: error: ld returned 1 exit status
   I don't know how to fix this. I'll update this when I figure it out.

[Elefant-Freeciv]

Issue 1, more affected files: MainInterfaceControls.cpp, MainInterfaceWorldView.cpp, Minimap.cpp, MainInterfaceEventHandling.cpp, CvPythonExtensions.cpp, TuiFileBrowser.cpp, TuiTextCode.cpp, VersionInfo.cpp. I think that's all.

[Elefant-Freeciv]

Just realized that there is a cmake_linker_type option in the cmake config command, and it is set to mold. So if that were to be changed, other linkers would probably work.

[fortsnek9348]

Just noticed this issue.

error: explicit qualification in declaration of

I do use explicit qualification in definitions. This should be valid C++, but I noticed that some compilers complain about it, which is why -Wno-extra-qualification is in the cmake script.

What's the full error? What compiler version are you using? Is it the latest version available?

Just realized that there is a cmake_linker_type option in the cmake config command, and it is set to mold. So if that were to be changed, other linkers would probably work.

Yes, that's in the build instructions, which also tells you to install mold. But that's only for faster linking compared to default LD.

mold: fatal: cannot open HeckTUIInputTest: Is a directory

I have no idea what could cause that.

I'll get back to this after christmas.

[Elefant-Freeciv]

mold: fatal: cannot open HeckTUIInputTest: Is a directory
This was caused by repeated rebuilds, if I remember correctly. Cleaning the build files fixed it.

[fortsnek9348]

If I won't get it from a clean rebuild, then I would probably need a list of steps to reproduce.

[Elefant-Freeciv]

I don't think there is any value in trying to debug it. With issues 2 and 3, I was largely trying to document them so others with the same issues can refer to this to solve them. As for issue 1, is there a specific reason to use explicit qualification?

[fortsnek9348]

Yeah, it seems gcc still doesn't accept explicit qualification on such code:

void f();
void ::f() {}

There was a DR a long time ago: https://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#482

And here's the GCC bug report: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64267

So as far as it seems, it's valid C++ and GCC is the odd one out. But they seem to be ignoring the bug.

Although, if you take the example at https://eel.is/c++draft/dcl.meaning#general-3.4, GCC compiles as it should. So maybe it's only a problem with global scope.

Explicit qualification is useful to prevent accidentally defining a new function at namespace scope. So I have instead moved some engine things to a new namespace in order to keep explicit qualification and satisfy GCC.

[fortsnek9348]

Changes pushed. See if you can build using g++15 or later and the latest code.