Question

My Lex file main.l:

%{
    #include <stdio.h>
%}
%%
start               printf("Start command received\n");
stop                printf("Stop command received\n");
%%

Create main.c file command:

> flex -Palone -omain.c main.l

Then try to compile it:

> gcc main.c -o main -lfl

and got the following errors:

  "_alonewrap", referenced from:
      _alonelex in ccdqmJjR.o
      _input in ccdqmJjR.o
  "_yylex", referenced from:
      _main in libfl.a(libmain.o)

How to compile the lex program created with the prefix?

Answer 1

If you use prefix, libfl is not for you. You must provide your own main function and your own <prefix>wrap function (or say you don’t want one with %option noyywrap, see flex manual).