yywrap it up

This weekend I decided to download the beta version of the highly anticipated Ubuntu 8.04.

After installing it on a virtual machine I promptly proceeded to building ZeroBUGS on it.

And I ran into a small roadblock: The debugger has a built-in C/C++ interpreter, for evaluating simple expressions and function calls. This code failed to link, because in this new Hardy Heron version of Ubuntu the yyFlexLexer class (see /usr/include/FlexLexer.h) has a virtual method called yywrap(). In older versions of flex yywrap used to be a standalone, extern "C" function.

To work around this issue in a portable manner I defined a new function in my configure.ac file.

It attempts to compile a small C++ program that assigns a pointer to method. If the compilation fails, I assume that yyFlexLexer::yywrap is not defined.

Here's the code:

AC_DEFUN([AC_YYFLEXLEXER_YYWRAP],
  [AC_CACHE_CHECK([for yyFlexLexer::yywrap],
             [ac_cv_yyFlexLexer_yywrap],
             [ac_cv_yyFlexLexer_yywrap=false
cat > tmp.cpp << ---end---

#include <FlexLexer.h>
int main()
{
  int (yyFlexLexer::*method)() = &yyFlexLexer::yywrap;
  return 0;
}
---end---
  if g++ tmp.cpp 2>/dev/null; then
      ac_cv_yyFlexLexer_yywrap=true
      rm a.out
  fi
  rm tmp.cpp])

  if test "$ac_cv_yyFlexLexer_yywrap" = true; then
      AC_DEFINE([HAVE_YYFLEXLEXER_YYWRAP], [1],
              [Define if yyFlexLexer::yywrap is declared])
  fi
])


AC_YYFLEXLEXER_YYWRAP

And you can test drive a pre-release of ZeroBUGS for Ubuntu 8.04 here: http://zero-bugs.com/8001/releases/zero_1.12-heron-032308_i386.deb

The md5sum is: 5b80e9f0f867b858620c740096e432dd