Re: [Flex-help] undefined reference to `yylex' when compiling as C++

[Filipp B. <b_...@zo...>]

Which header is that? I tried to include FlexLexer.h but then the
compiler says that I am trying to redefine class.


On 08.10.2014 15:03, Will Estes wrote:
> Looks like you need to include the flex c++ header so that you have a c++ lexer function, if I'm reading your example right.
> 
> On Wednesday,  8 October 2014,  9:23 am +0400, "Filipp B." <b_...@zo...> wrote:
> 
>> Hello. I am just starting with flex and trying to compile a simple
>> program, no bison yet.
>>
>> /* calc.l */
>>
>> %{
>> #include <iostream>
>> #include <exception>
>> %}
>>
>> %option debug
>> %option nodefault
>> %option noyywrap
>> %option c++
>>
>> %%
>> \+          {
>>                 std::cout << "PLUS" << std::endl;
>>             }
>>
>> \*          {
>>                 std::cout << "MULTIPLY" << std::endl;
>>             }
>>
>> -           {
>>                 std::cout << "MINUS" << std::endl;
>>             }
>>
>> \/          {
>>                 std::cout << "DIVIDE" << std::endl;
>>             }
>>
>> .|\n        {
>>                 std::terminate();
>>             }
>> %%
>>
>> /* calc.l end */
>>
>> The problem is the following:
>>
>> $ flex calc.l && g++ lex.yy.cc -lfl
>> /usr/lib/gcc/x86_64-pc-linux-gnu/4.8.3/../../../../lib64/libfl.a(libmain.o):
>> In function `main':
>> libmain.c:(.text.startup+0xb): undefined reference to `yylex'
>> collect2: error: ld returned 1 exit status
>>
>>
>> Writing pure C code using printf instead, with no %option c++, and
>> compiling it with gcc works fine, but this doesn't. Why?
>>
>> -- 
>> Filipp B.
>>
>>
>> ------------------------------------------------------------------------------
>> Meet PCI DSS 3.0 Compliance Requirements with EventLog Analyzer
>> Achieve PCI DSS 3.0 Compliant Status with Out-of-the-box PCI DSS Reports
>> Are you Audit-Ready for PCI DSS 3.0 Compliance? Download White paper
>> Comply to PCI DSS 3.0 Requirement 10 and 11.5 with EventLog Analyzer
>> http://pubads.g.doubleclick.net/gampad/clk?id=154622311&iu=/4140/ostg.clktrk
>> -- 
>> Flex-help mailing list
>> Fle...@li...
>> https://lists.sourceforge.net/lists/listinfo/flex-help

-- 
Filipp B.