Description of Problem:

Output of the C++ version of Flex is not compatible with G++ 3.

Version-Release number of selected component (if applicable):

flex-2.5.4a-15

How Reproducible:

Create a C++ lexer. The output will contain:

  #ifdef __cplusplus

  #include <stdlib.h>
  class istream;

this causes barfage for g++-3

In file included from /usr/include/FlexLexer.h:47,
                 from out/lexer.cc:240:
/usr/include/g++-v3/backward/iostream.h:36: using directive `istream' 
   introduced ambiguous type `istream'
lexer.ll: In member function `virtual int My_lily_lexer::yylex()':
lexer.ll:497: cannot convert `std::istream*' to `istream*' in assignment
lexer.ll: In member function `void yyFlexLexer::yy_load_buffer_state()':
lexer.ll:1020: cannot convert `istream*' to `std::istream*' in assignment
lexer.ll: In member function `void 
   yyFlexLexer::yy_init_buffer(yy_buffer_state*, std::istream*)':
lexer.ll:1070: cannot convert `std::istream*' to `istream*' in assignment


the fix is to replace 

  class istream;

with

  #include <iostream.h>