Is there a simple way to convert C++ enum to string?

Question

Suppose we have some named enums:

enum MyEnum {
      FOO,
      BAR = 0x50
};

What I googled for is a script (any language) that scans all

Answer 1

The following ruby script attempts to parse the headers and builts the required sources alongside the original headers.

#! /usr/bin/env ruby

# Let's "parse" the headers
# Note that using a regular expression is rather fragile
# and may break on some inputs

GLOBS = [
  "toto/*.h",
  "tutu/*.h",
  "tutu/*.hxx"
]

enums = {}
GLOBS.each { |glob|
  Dir[glob].each { |header|
    enums[header] = File.open(header, 'rb') { |f|
      f.read
    }.scan(/enum\s+(\w+)\s+\{\s*([^}]+?)\s*\}/m).collect { |enum_name, enum_key_and_values|
      [
        enum_name, enum_key_and_values.split(/\s*,\s*/).collect { |enum_key_and_value|
          enum_key_and_value.split(/\s*=\s*/).first
        }
      ]
    }
  }
}


# Now we build a .h and .cpp alongside the parsed headers
# using the template engine provided with ruby
require 'erb'

template_h = ERB.new <<-EOS
#ifndef <%= enum_name %>_to_string_h_
#define <%= enum_name %>_to_string_h_ 1

#include "<%= header %>"
char* enum_to_string(<%= enum_name %> e);

#endif
EOS

template_cpp = ERB.new <<-EOS
#include "<%= enum_name %>_to_string.h"

char* enum_to_string(<%= enum_name %> e)
{
  switch (e)
  {<% enum_keys.each do |enum_key| %>
    case <%= enum_key %>: return "<%= enum_key %>";<% end %>
    default: return "INVALID <%= enum_name %> VALUE";
  }
}
EOS

enums.each { |header, enum_name_and_keys|
  enum_name_and_keys.each { |enum_name, enum_keys|
    File.open("#{File.dirname(header)}/#{enum_name}_to_string.h", 'wb') { |built_h|
      built_h.write(template_h.result(binding))
    }

    File.open("#{File.dirname(header)}/#{enum_name}_to_string.cpp", 'wb') { |built_cpp|
      built_cpp.write(template_cpp.result(binding))
    }
  }
}

Using regular expressions makes this "parser" quite fragile, it may not be able to handle your specific headers gracefully.

Let's say you have a header toto/a.h, containing definitions for enums MyEnum and MyEnum2. The script will build:

toto/MyEnum_to_string.h
toto/MyEnum_to_string.cpp
toto/MyEnum2_to_string.h
toto/MyEnum2_to_string.cpp

More robust solutions would be:

• Build all sources defining enums and their operations from another source. This means you'll define your enums in a XML/YML/whatever file which is much easier to parse than C/C++.
• Use a real compiler such as suggested by Avdi.
• Use preprocessor macros with or without templates.