Retrieve test for %l of mrb_vformat(); ref #4613

[shuujii]

The following compilation error occurs on Visual Studio 2017 in AppVeyor if
commented out part in previous mrbgems/mruby-test/vformat.c is enabled.

CC    mrbgems/mruby-test/vformat.c -> build/cxx_abi/mrbgems/mruby-test/vformat.obj
  C:\projects\mruby\mrbgems\mruby-test\vformat.c(176): fatal error C1060: compiler is out of heap space
  INTERNAL COMPILER ERROR in 'C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.16.27023\bin\HostX64\x64\cl.exe'
      Please choose the Technical Support command on the Visual C++
      Help menu, or open the Technical Support help file for more information

This error seems to occur only C++, and not occur Visual Studio 2013/2015.

The cause seems to be deep nested conditional operator (? :). So I decided
to generate mrbgems/mruby-test/vformat.c with ERB to avoid it.

[matz]

Introducing more dependency (erb) is not preferable. Is there any other workaround?

[shuujii]

I didn't use erb command but ERB library which is a Ruby standard library, so I thought it was acceptable.

If it is not acceptable, what about the following actions?

• Commit the generated file like lex.def as well.

• Incorporates a small template engine implementation such as Mote, Ate and Erubi. If we only support % and <%= ... %> (newlines are not allowed), the following one-liner can also be used :)

  # one-liner-erb.rb
  eval$<.map{|l|l=~/^%/?$':%|$><<"#{l.gsub(/<%=(.*?)%>/,'#{\1}')}"|}*$/

  %# example.erb
  % native_types = {
  %   c: {type: "char", code: "RSTRING_PTR(obj)[0]"},
  %   d: {type: "int" , code: "(int)mrb_fixnum(obj)"},
  % }
  typedef struct {
  % native_types.each do |spec, attrs|
    <%=attrs[:type]%> <%=spec%>;
  % end
  } VFNative;

  $ ruby one-liner-erb.rb example.erb
  typedef struct {
    char c;
    int d;
  } VFNative;
  
  $ diff -s =(ruby one-liner-erb.rb example.erb) =(erb example.erb)
  Files /tmp/zshq5HoG1 and /tmp/zshuoc8X6 are identical

[matz]

I addressed this issue in a different way.