Re: socklen_t data type

Keith Marshall <[email protected]> Mon, 6 Jul 2020 16:11:23 +0100
Newsgroups	gmane.comp.gnu.mingw.user
Organization	MinGW.org Project
Message-ID	<[email protected]>
On 30/06/2020 15:23, Eli Zaretskii wrote:
>> From: Keith Marshall, Tue, 30 Jun 2020 07:54:18 +0100
>>
>>> GDB is a C++ program these days, and is compiled with -fpermissive, so
>>> this causes errors.
>>
>> Surely -fpermissive relaxes the error checking for type conflicts,
>> (possibly among other conditions -- I don't know what its scope is), so
>> such errors would be downgraded to warnings.  Do you, perhaps, mean that
>> GDB is compiled _without_ -fpermissive?
> 
> You are probably right.  All I know is that g++ emitted this:
> 
>     CXX    remote-utils.o
>   remote-utils.cc: In function 'void handle_accept_event(int, gdb_client_data)':
>   remote-utils.cc:146:69: error: invalid conversion from 'socklen_t*' {aka 'unsigned int*'} to 'int*' [-fpermissive]
>     146 |   remote_desc = accept (listen_desc, (struct sockaddr *) &sockaddr, &len);
> 	|                                                                     ^~~~
> 	|                                                                     |
> 	|                                                                     socklen_t* {aka unsigned int*}
> 
> I guess I mis-interpreted what that confusing message means to say.

Indeed, it does appear that the error arises because -fpermissive is
enabled, but when I compiled my own test program _without_ -fpermissive,
I got a similar message; when I compiled _with_ -fpermissive, I got the
same message, but downgraded from error to warning.

>> There's more to it.  As I reported in:
>>
>>    https://savannah.gnu.org/bugs/?57725
>>
>> a primary motivator for the change to unsigned socklen_t was to avoid a
>> proliferation of casts in <wspiapi.h>, (of which, at the time, I seemed
>> to be writing quite a number).  Reviewing it again, I seem to have ended
>> up with only one such cast which remains necessary, at line 917:
>>
>>    if( (sa == NULL) || (len < sizeof( struct sockaddr )) )
>>
>> With reversion to signed socklen_t, this should become:
>>
>>    if( (sa == NULL) || (len < (socklen_t)(sizeof( struct sockaddr ))) )
> 
> You are a better judge of this, but to my mind a single cast is a
> small price to pay for avoiding the kind of mess I faced yesterday,
> with socklen_t popping up in compilation errors left and right.
> 
> Gnulib already removed the unnecessary conflicting typedef, and I will
> shortly report the problem in the GDB sources to its developers.  But
> I think the problems with code which assumes the last argument of
> 'accept' and its ilk could be a 'socklen_t *' are a much harder nut,
> and so going back to a signed int will be a good compromise.

I've made that change, (both change of typedef, and the corresponding
cast), in wsl-5.3.4, which I've uploaded to FRS this morning.

-- 
Regards,
Keith.

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