Re: [Flex-help] Error changing yylex return.

[Fabricio S. P. <fab...@gm...>]

I did some test to discovery what is going on.
I forward declared the new yylex inside my main file and everything went 
OK. For some reason flex is not including the new declaration inside the 
header file.

Here some simple example in gist [1]. The file main2.c is main.c after 
gcc preprocessor "gcc -E"

The generated header file has the new yylex declaration:
 >#ifndef yyHEADER_H
 >#define yyHEADER_H 1
 >#define yyIN_HEADER 1
 >
 >#line 2 "flex.l"
 >#define YY_DECL double yylex(yyscan_t yyscanner)
 >
 >
 >
 >#line 11 "lex.yy.h"

But after passing through compiler preprocessor it's removed, as you can 
see in the main2.c file, and I have to forward declared the new 
function. I don't know if this is the correct behavior or is a bug.

[1] https://gist.github.com/anonymous/ec6d47fe8d7822f0e554


On 02/29/2016 10:37 PM, Chris verBurg wrote:
> Hey Fabricio,
>
> To first order, your code all looks fine to me.  It seems like your
> redeclaration is not making it into main.c -- I'd suggest maybe next
> looking at the generated flex.h and seeing what it's doing with YY_DECL and
> yylex.  Maybe your %{..%} block has to be moved earlier or later in the
> first section?
>
> -Chris
>
>
>
> On Mon, Feb 29, 2016 at 2:06 PM, Fabricio S. Paranhos <
> fab...@gm...> wrote:
>
>> Hello,
>>
>> I'm trying to change the default return value (int) from yylex to a
>> structure. According to FLEX manual it's possible to change how yylex is
>> declared[1]:
>>
>>   >This definition may be changed by defining the YY_DECL macro. For
>>   >example, you could use:
>>   >
>>   >         #define YY_DECL float lexscan( a, b ) float a, b;
>>   >
>>
>> In my flex file I declared this way:
>>
>>   >#define YY_DECL struct token yylex(yyscan_t yyscanner)
>>
>> But after using this macro and compiling the final main program I got
>> the following GCC error:
>>
>>   >main.c: In function ‘main’:
>>   >main.c:14:7: error: incompatible types when assigning to type ‘struct
>>   >token’ from type ‘int’
>>   >   lol = yylex(scanner);
>>
>>
>> Even after changing how yylex is declared the final result didn't
>> change. After some search on the web I found this[2] stack overflow
>> question, but I got the same error from GCC...
>>
>> Anybody can help?
>>
>> Here are some additional info:
>> OS:   Debian 8 64bit
>> GCC:  Debian 4.9.2-10 4.9.2
>> Flex: 2.5.39
>>
>> And here are my source files:
>> https://gist.github.com/anonymous/49beeae0d85b4a7f91d6
>>
>> Thanks in advance.
>>
>> [1]
>> http://flex.sourceforge.net/manual/Generated-Scanner.html#Generated-Scanner
>> [2]
>> https://stackoverflow.com/questions/3796598/returning-non-ints-from-yylex
>> --
>> Fabrício S. Paranhos
>>
>>
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>

-- 
Fabrício S. Paranhos