Ubuntu 20.04 compatibility

[ppenzin]

• Drive by cleanup: Build all wabt files in the build directory

[ppenzin]

This is not all, there are other errors coming from both palrt and the main sources. I think this is due to newer Clang being more pedantic about C++ type compatibility.

I am not sure why the definitions in pal.h in needed, but I need to get through the entire build to find out.

[rhuanjl]

These defines are wrapped in a #ifndef PAL_STDCPP_COMPAT could we try defining PAL_STDCPP_COMPAT and seeing if that fixes things?

[ppenzin]

We do define that, but not for PAL sources. I tried adding this to PAL, but things did not go well with definitions in palinternal.h. Using C99 standard does not help with this issue either, as it is not getting passed to C++ files.

I was able to get through a number of template parameter errors, but now stuck back in PAL on malloc/free/realloc, which PAL reimplements.

I am also bumping Ubuntu CI version, so that we can see the progress. Also, given the situation, maybe we should test with both 18.04 and 20.04.

[ppenzin]

I tried to be consistent with these - the main goal is to simply give a different name to template parameters, so that they don't collide in situations like this:

template<class T>
class Foo {
  // Can't use the same name (T) here
  template<class T>
  friend class Bar;

  // ... and here
  template<class T>
  void Baz (T arg);
};

[ppenzin]

It was late at night and I changed Ubuntu image on copyright check job instead of builds. Also dropping PAL definitions change for now, will experiment and come up with something better.

[rhuanjl]

Interesting that Pal definitions are clashing with the Ubuntu stdlib. Could we just try deleting all the methods in pal that are in the stdlib?

[ppenzin]

If/when CI finishes it can be reviewed. I have added two more jobs for Ubuntu 18.04, not sure if they are needed, but thought it won't hurt since there are toolchain changes between those two versions.

Edit: never mind, style check failed, as I forgot to update the copyright. Hold on tight.

[ppenzin]

Now as one big commit. There are mostly two things in it - template parameter disambiguation and PAL definition removal. It also adds two CI jobs for 18.04 and cleans up Wabt build set up.

[rhuanjl]

I agree we need the coverage - and let's take this in for now BUT I wonder if we could trim down slightly - maybe do debug on one platform and RelWithDebInfo on the other or something to reduce the CI run time.