[ragel-users] C++11, new narrowing rules and unsigned char on ARM

[Jan Kundrát]

Hi, I was wondering if anybody read the mail (quoted below) which I sent 
last month. I do see some commits in the git repository, but I haven't 
received an answer to my bugreport yet.

With kind regards,
Jan


On Wednesday, 18 September 2013 16:05:39 CEST, Jan Kundrát wrote:
> Hi Adrian,
> I'm using Ragel for parsing of e-mail headers as per RFC5322. 
> When porting this project to ARM (MeeGo Harmattan, Nokia N9), 
> I've noticed that it fails to build after I enable C++11 
> features using clang 3.3. Here is the error message:
>
> /home/jkt/work/prog/trojita/_build_harmattan/Rfc5322HeaderParser.generated.cpp:164:26: 
> error: constant expression evaluates to -128 which cannot be 
> narrowed to type 'char' [-Wc++11-narrowing]
>         39, 42, 127, 10, 9, 32, -128, -1,                       
>           ^~~~
> /home/jkt/work/prog/trojita/_build_harmattan/Rfc5322HeaderParser.generated.cpp:164:26: 
> note: override this message by inserting an explicit cast
>         39, 42, 127, 10, 9, 32, -128, -1,                       
>           ^~~~
>                                 static_cast<char>( )
>
> So the problem is that the signedness rules for the host 
> (machine running ragel producing the .cpp file with parser) and 
> target (the target platform of the C++ compiler which is 
> producing Ragel's output) do not match. That's a big problem, 
> and it isn't limited just to chars, actually -- because Ragel's 
> code uses platform's native types instead of the portable ones, 
> there's no guarantee that ragel's int can fit the data of the 
> target's size, etc. I've solved this by patching ragel to use 
> C's int<num>_t types, please see the commit at [1]. That patch 
> fixes my problem.
>
> In addition, before I realized that I'm actually looking for 
> the ragel-6 branch, I spent some time playing with master before 
> I finding out that it's some kind of a rewrite. The same bug 
> applies there as well. Before I was able to get the master 
> branch to build on my system, I had to make the following 
> changes:
>
> * Fixing a build failure due to a bug in colm's headers [2]. I 
> see you're upstream for that project, too, perhaps you can fix 
> it in there as well.
>
> * Making sure that version.h is generated [3].
>
> After that, I simply added a rule to always treat chars as 
> signed [4]. That's arguably a wrong change; the code shall 
> probably do the same thing as [1]. I don't have time for this 
> now.
>
> And finally, when I tried the patched master, I found out that 
> my ragel parser won't compile anymore -- please see the file at 
> [5]. The error message I get is that it cannot find the "CRLF" 
> symbol which is defined in the included .rl file [6]. That looks 
> like a regression in the rewrite.
>
> Thanks for a cool software -- I hope these patches are OK and 
> that you'll merge them.
>
> Cheers,
> Jan
>
> [1]  
> http://repo.or.cz/w/ragel-jkt.git/commitdiff/dc238e78cd3024889b6fb2618fe5bbc20179a132
> [2] 
> http://repo.or.cz/w/ragel-jkt.git/commitdiff/faee23876c6b5abde368355e14d786aba2300d4c
> [3] 
> http://repo.or.cz/w/ragel-jkt.git/commitdiff/a980ec473ee66ecb6dd3cc972819c33da8d1a8d7
> [4] 
> http://repo.or.cz/w/ragel-jkt.git/commitdiff/06fab1367f2b3d6df6d51aa2cfeb97737617fa19
> [5] 
> http://quickgit.kde.org/?p=trojita.git&a=blob&h=efb0307c829d1c0c7939a556dd40427779221651&hb=e6dd1668fbebd3f3e676f17a5ac2acde99629ca7&f=src/Imap/Parser/Rfc5322HeaderParser.cpp
> [6] 
> http://quickgit.kde.org/?p=trojita.git&a=blob&h=65e67a87c727714783bd793b43824795d0e94ef6&hb=e6dd1668fbebd3f3e676f17a5ac2acde99629ca7&f=src/Imap/Parser/rfc5322.rl
>

-- 
Trojitá, a fast Qt IMAP e-mail client -- http://trojita.flaska.net/

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