%option c++ is not compatible with %option noyywrap - linker error: multiple definition

[ghost]

There seems to be a bug in flex (master) for C++ scanner generation at in src/main.c at line 1679:

 		if (!do_yywrap) {
			outn("\nint yyFlexLexer::yywrap() { return 1; }");
		}

The definition of yyFlexLexer::yywrap() appears in both the header and implementation file. Prefixing with inline solves the problem, but maybe a better solution would be to only output to the implementation file?

[ghost]

@lexxmark maybe you would be interested in applying the same fix to win_flex?

[ghost]

Just to clarify the issue is with the header generated by flex, as shown in this example program:

lexer_bug.l:

%option c++ noyywrap outfile="ScannerX.cpp" header="ScannerX.hpp"

%%

.	return 0;

main.cpp:

#include "ScannerX.hpp"

int main() {
    FlexLexer *lex = new yyFlexLexer;
    lex->yylex();
}

$ flex lexer_bug.l
$ g++ ScannerX.cpp main.cpp
/usr/bin/ld: /tmp/cc2Aqsft.o: in function `yyFlexLexer::yywrap()':
main.cpp:(.text+0x0): multiple definition of `yyFlexLexer::yywrap()'; /tmp/ccmi47fP.o:ScannerX.cpp:(.text+0x0): first defined here
collect2: error: ld returned 1 exit status

Two solutions are to #include <FlexLexer.h> instead or the fix to src/main.c above. I still believe the code is broken however, as it generates a header which cannot safely be referenced.