nsc 0.5.3 compilation error with flex

[Luca Barbierato]

Dear all,

I'm trying to compile NSC to add it in my ns-3-dev build. Once I clone the repository through:

hg clone https://secure.wand.net.nz/mercurial/nsc

And I run the python code:

python scons.py

I'm experiencing this error:

scons: Reading SConscript files ...

Checking target architecure...(cached) amd64, checking userland ...amd64

Checking for C library fl... yes

scons: done reading SConscript files.

scons: Building targets ...

flex -t globaliser/lexer.l > globaliser/lexer.lex.cc

bison --defines=globaliser//parser.tab.hh globaliser/parser.yc -o globaliser/parser.tab.cc

globaliser/parser.yc: warning: 1 shift/reduce conflict [-Wconflicts-sr]

g++ -o globaliser/lexer.lex.o -c -Wall -g -O globaliser/lexer.lex.cc

g++ -o globaliser/parser.tab.o -c -Wall -g -O globaliser/parser.tab.cc

g++ -o globaliser/ilex.o -c -Wall -g -O globaliser/ilex.cc

g++ -o globaliser/handle_global.o -c -Wall -g -O globaliser/handle_global.cc

g++ -o globaliser/node.o -c -Wall -g -O globaliser/node.cc

globaliser/node.cc: In member function 'bool node_t::handle_global(std::__cxx11::string, std::__cxx11::list<std::__cxx11::basic_string<char> >*, std::__cxx11::list<std::__cxx11::basic_string<char> >*)':

globaliser/node.cc:906:36: warning: variable 'str_start' set but not used [-Wunused-but-set-variable]

               string::size_type i, str_start, str_end;

                                    ^

globaliser/node.cc:772:40: warning: variable 'declarator' set but not used [-Wunused-but-set-variable]

             *initialiser_node = NULL, *declarator = NULL;

                                        ^

globaliser/node.cc:483:9: warning: variable 'orig_newlines' set but not used [-Wunused-but-set-variable]

     int orig_newlines;

         ^

g++ -o globaliser/globaliser globaliser/lexer.lex.o globaliser/parser.tab.o globaliser/ilex.o globaliser/handle_global.o globaliser/node.o -lfl

/usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/libfl.so: undefined reference to `yylex'

collect2: error: ld returned 1 exit status

scons: *** [globaliser/globaliser] Error 1

scons: building terminated because of errors.

Here my environment details:

Ubuntu Version: 18.04.1 LTS

Python Version: 2.7.15rc1
NSC Version:    0.5.3

flex Version:   2.6.4
bison Version:  3.0.4
g++ Version:    5.5.0 20171010 (Ubuntu 5.5.0-12ubuntu1) (downgraded from g++-7 because NSC requires use of gcc-4.9 or gcc-5 series)

Could somebody help me to solve the problem?