Re: openCOLLADA: Help with GCC6 narrowing conversion

[Ralf Corsepius]

On 02/19/2016 12:05 AM, David Woodhouse wrote:

On Mon, 2016-02-15 at 17:09 +0100, Ralf Corsepius wrote:

Exactly. Because of this, I -fsigned-char should only be applied as a
last resort/work-around to mere program/application packages and not to
library packages, IMHO.

Or to programs which *use* libraries? :)


Sure.

What I was referring to is -fsigned-char should not be applied to 
library/header packages,
because this would propagate this -fsigned-char into users/consumers of 
these library

packages.

Ralf
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Re: openCOLLADA: Help with GCC6 narrowing conversion

[Kevin Kofler]

Dan Horák wrote:
> you are welcome, there will be more packages suffering from the same
> problem (I own at least one :-)), sometimes appending "-fsigned-char"
> to CFLAGS will be easier.

It is also possible to just get rid of the narrowing error with:
-Wno-error=narrowing
but that will only restore the previous GCC behavior. It will NOT make the 
program magically work if it later checks for -1 with something like
"if (HEX2DEC[i] < 0)" (which never worked on ARM without -fsigned-char or 
explicitly writing "signed char").

There are other cases where -Wno-error=narrowing is the most effective fix, 
but char x[]={-1} is a case where the narrowing error is really only 
uncovering a deeper issue.

Kevin Kofler
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Re: openCOLLADA: Help with GCC6 narrowing conversion

[David Woodhouse]

On Mon, 2016-02-15 at 17:09 +0100, Ralf Corsepius wrote:
> 
> Exactly. Because of this, I -fsigned-char should only be applied as a 
> last resort/work-around to mere program/application packages and not to 
> library packages, IMHO.

Or to programs which *use* libraries? :)

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Re: openCOLLADA: Help with GCC6 narrowing conversion

[Jonathan Wakely]

On 16/02/16 10:51 +, Jonathan Wakely wrote:

Given that there are dozens of those initializers it might be more
readable to do:

static const char none = -1;
const char HEX2DEC[256] = { none, none, none, . }


For the avoidance of doubt, this is not an error in C++11.

Narrowing conversions are only erorrs when they appear inside a
braced-init-list. So 'none' is initialized to (char)-1 without error,
then the elements of the HEX2DEC array are initialized from char
values that need no conversion, so also without error.

The original code required -1 to be converted to char inside the
braqced-init-list for HEX2DEC.
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Re: openCOLLADA: Help with GCC6 narrowing conversion

[Jonathan Wakely]

On 15/02/16 23:46 +0900, Mamoru TASAKA wrote:

Richard Shaw wrote on 02/15/2016 11:34 PM:

Can someone point me in the right direction? My package openCOLLADA is
FTBFS in rawhide with the following (repeating) error:

/builddir/build/BUILD/OpenCOLLADA-3335ac164e68b2512a40914b14c74db260e6ff7d/COLLADABaseUtils/src/COLLADABUURI.cpp:57:2:
error: narrowing conversion of '-1' from 'int' to 'char' inside { }
[-Wnarrowing]
  };

I tried using the gcc6 porting guide but I'm not qutie enough of a
programmer to understand how to apply it in this case. The offending code
is:

const char HEX2DEC[256] = ^M
{^M
/*   0  1  2  3   4  5  6  7   8  9  A  B   C  D  E  F
*/^M
/* 0 */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-1,-1,-1,-1,^M
/* 1 */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,




On _ARM_ (actually build failure seems to be on ARM) char is _unsigned_
by default, so converting (int)-1 to char on ARM is narrowing conversion
and C++11 forbids this on list-initialization.

You can do this when you explicitly cast, like
const char HEX2DEC[256] = { (char)-1, . }


Given that there are dozens of those initializers it might be more
readable to do:

static const char none = -1;
const char HEX2DEC[256] = { none, none, none, . }
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Re: openCOLLADA: Help with GCC6 narrowing conversion

[Jonathan Wakely]

On 16/02/16 01:34 +0100, Michael Schwendt wrote:

On Mon, 15 Feb 2016 16:46:32 +0100, Dan Horák wrote:


you are welcome, there will be more packages suffering from the same
problem (I own at least one :-)), sometimes appending "-fsigned-char"
to CFLAGS will be easier.


A couple of narrowing-conversion problems had turned up in Oct 2015
already, so this is nothing new to GCC 6.


Right, the problem is C++11 or later, not GCC 6.

It's likely the Oct 2015 problems were in packages that switched to
-std=gnu++11 (or a similar flag) with GCC 5.
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Re: openCOLLADA: Help with GCC6 narrowing conversion

[Michael Schwendt]

On Mon, 15 Feb 2016 16:46:32 +0100, Dan Horák wrote:

> you are welcome, there will be more packages suffering from the same
> problem (I own at least one :-)), sometimes appending "-fsigned-char"
> to CFLAGS will be easier.

A couple of narrowing-conversion problems had turned up in Oct 2015
already, so this is nothing new to GCC 6.
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Re: openCOLLADA: Help with GCC6 narrowing conversion

[Ralf Corsepius]

On 02/15/2016 04:54 PM, Jakub Jelinek wrote:

On Mon, Feb 15, 2016 at 04:46:32PM +0100, Dan Horák wrote:

On Mon, 15 Feb 2016 09:35:03 -0600
Richard Shaw  wrote:


On Mon, Feb 15, 2016 at 8:50 AM, Dan Horák  wrote:


On Mon, 15 Feb 2016 08:34:31 -0600
Richard Shaw  wrote:


Can someone point me in the right direction? My package
openCOLLADA is FTBFS in rawhide with the following (repeating)
error:



/builddir/build/BUILD/OpenCOLLADA-3335ac164e68b2512a40914b14c74db260e6ff7d/COLLADABaseUtils/src/COLLADABUURI.cpp:57:2:

error: narrowing conversion of '-1' from 'int' to 'char' inside
{ } [-Wnarrowing]
   };


isn't it on ARM? Then you should use explicit "signed char" as char
is unsigned by default on ARM (and other arches), see eg.
http://blog.cdleary.com/2012/11/arm-chars-are-unsigned-by-default/



Thanks Dan, that got it, adding an explicit signed fixed the build.


you are welcome, there will be more packages suffering from the same
problem (I own at least one :-)), sometimes appending "-fsigned-char"
to CFLAGS will be easier.


Note that -fsigned-char changes the ABI, so it might have various
undesirable effects too.


Exactly. Because of this, I -fsigned-char should only be applied as a 
last resort/work-around to mere program/application packages and not to 
library packages, IMHO.


Ralf
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Re: openCOLLADA: Help with GCC6 narrowing conversion

[Jakub Jelinek]

On Mon, Feb 15, 2016 at 04:46:32PM +0100, Dan Horák wrote:
> On Mon, 15 Feb 2016 09:35:03 -0600
> Richard Shaw  wrote:
> 
> > On Mon, Feb 15, 2016 at 8:50 AM, Dan Horák  wrote:
> > 
> > > On Mon, 15 Feb 2016 08:34:31 -0600
> > > Richard Shaw  wrote:
> > >
> > > > Can someone point me in the right direction? My package
> > > > openCOLLADA is FTBFS in rawhide with the following (repeating)
> > > > error:
> > > >
> > > >
> > > /builddir/build/BUILD/OpenCOLLADA-3335ac164e68b2512a40914b14c74db260e6ff7d/COLLADABaseUtils/src/COLLADABUURI.cpp:57:2:
> > > > error: narrowing conversion of '-1' from 'int' to 'char' inside
> > > > { } [-Wnarrowing]
> > > >   };
> > >
> > > isn't it on ARM? Then you should use explicit "signed char" as char
> > > is unsigned by default on ARM (and other arches), see eg.
> > > http://blog.cdleary.com/2012/11/arm-chars-are-unsigned-by-default/
> > 
> > 
> > Thanks Dan, that got it, adding an explicit signed fixed the build.
> 
> you are welcome, there will be more packages suffering from the same
> problem (I own at least one :-)), sometimes appending "-fsigned-char"
> to CFLAGS will be easier.

Note that -fsigned-char changes the ABI, so it might have various
undesirable effects too.

Jakub
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Re: openCOLLADA: Help with GCC6 narrowing conversion

[Dan Horák]

On Mon, 15 Feb 2016 09:35:03 -0600
Richard Shaw  wrote:

> On Mon, Feb 15, 2016 at 8:50 AM, Dan Horák  wrote:
> 
> > On Mon, 15 Feb 2016 08:34:31 -0600
> > Richard Shaw  wrote:
> >
> > > Can someone point me in the right direction? My package
> > > openCOLLADA is FTBFS in rawhide with the following (repeating)
> > > error:
> > >
> > >
> > /builddir/build/BUILD/OpenCOLLADA-3335ac164e68b2512a40914b14c74db260e6ff7d/COLLADABaseUtils/src/COLLADABUURI.cpp:57:2:
> > > error: narrowing conversion of '-1' from 'int' to 'char' inside
> > > { } [-Wnarrowing]
> > >   };
> >
> > isn't it on ARM? Then you should use explicit "signed char" as char
> > is unsigned by default on ARM (and other arches), see eg.
> > http://blog.cdleary.com/2012/11/arm-chars-are-unsigned-by-default/
> 
> 
> Thanks Dan, that got it, adding an explicit signed fixed the build.

you are welcome, there will be more packages suffering from the same
problem (I own at least one :-)), sometimes appending "-fsigned-char"
to CFLAGS will be easier.


Dan
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Re: openCOLLADA: Help with GCC6 narrowing conversion

[Richard Shaw]

On Mon, Feb 15, 2016 at 8:50 AM, Dan Horák  wrote:

> On Mon, 15 Feb 2016 08:34:31 -0600
> Richard Shaw  wrote:
>
> > Can someone point me in the right direction? My package openCOLLADA is
> > FTBFS in rawhide with the following (repeating) error:
> >
> >
> /builddir/build/BUILD/OpenCOLLADA-3335ac164e68b2512a40914b14c74db260e6ff7d/COLLADABaseUtils/src/COLLADABUURI.cpp:57:2:
> > error: narrowing conversion of '-1' from 'int' to 'char' inside { }
> > [-Wnarrowing]
> >   };
>
> isn't it on ARM? Then you should use explicit "signed char" as char is
> unsigned by default on ARM (and other arches), see eg.
> http://blog.cdleary.com/2012/11/arm-chars-are-unsigned-by-default/


Thanks Dan, that got it, adding an explicit signed fixed the build.

Thanks,
Richard
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Re: openCOLLADA: Help with GCC6 narrowing conversion

[Dan Horák]

On Mon, 15 Feb 2016 08:34:31 -0600
Richard Shaw  wrote:

> Can someone point me in the right direction? My package openCOLLADA is
> FTBFS in rawhide with the following (repeating) error:
> 
> /builddir/build/BUILD/OpenCOLLADA-3335ac164e68b2512a40914b14c74db260e6ff7d/COLLADABaseUtils/src/COLLADABUURI.cpp:57:2:
> error: narrowing conversion of '-1' from 'int' to 'char' inside { }
> [-Wnarrowing]
>   };

isn't it on ARM? Then you should use explicit "signed char" as char is
unsigned by default on ARM (and other arches), see eg.
http://blog.cdleary.com/2012/11/arm-chars-are-unsigned-by-default/


Dan
 
> I tried using the gcc6 porting guide but I'm not qutie enough of a
> programmer to understand how to apply it in this case. The offending
> code is:
> 
> const char HEX2DEC[256] = ^M
> {^M
> /*   0  1  2  3   4  5  6  7   8  9  A  B   C  D
> E  F */^M
> /* 0 */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
> -1,-1,-1,-1,^M
> /* 1 */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
> -1,-1,-1,-1,^M
> /* 2 */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
> -1,-1,-1,-1,^M
> /* 3 */  0, 1, 2, 3,  4, 5, 6, 7,  8, 9,-1,-1,
> -1,-1,-1,-1,^M
> ^M
> /* 4 */ -1,10,11,12, 13,14,15,-1, -1,-1,-1,-1,
> -1,-1,-1,-1,^M
> /* 5 */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
> -1,-1,-1,-1,^M
> /* 6 */ -1,10,11,12, 13,14,15,-1, -1,-1,-1,-1,
> -1,-1,-1,-1,^M
> /* 7 */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
> -1,-1,-1,-1,^M
> ^M
> /* 8 */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
> -1,-1,-1,-1,^M
> /* 9 */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
> -1,-1,-1,-1,^M
> /* A */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
> -1,-1,-1,-1,^M
> /* B */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
> -1,-1,-1,-1,^M
> ^M
> /* C */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
> -1,-1,-1,-1,^M
> /* D */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
> -1,-1,-1,-1,^M
> /* E */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
> -1,-1,-1,-1,^M
> /* F */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
> -1,-1,-1,-1^M };^M
> 
> Thanks,
> Richard
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Re: openCOLLADA: Help with GCC6 narrowing conversion

[Richard Shaw]

On Mon, Feb 15, 2016 at 8:46 AM, Mamoru TASAKA 
wrote:

> Richard Shaw wrote on 02/15/2016 11:34 PM:
>
>> Can someone point me in the right direction? My package openCOLLADA is
>> FTBFS in rawhide with the following (repeating) error:
>>
>>
>> /builddir/build/BUILD/OpenCOLLADA-3335ac164e68b2512a40914b14c74db260e6ff7d/COLLADABaseUtils/src/COLLADABUURI.cpp:57:2:
>> error: narrowing conversion of '-1' from 'int' to 'char' inside { }
>> [-Wnarrowing]
>>};
>>
>> I tried using the gcc6 porting guide but I'm not qutie enough of a
>> programmer to understand how to apply it in this case. The offending code
>> is:
>>
>>  const char HEX2DEC[256] = ^M
>>  {^M
>>  /*   0  1  2  3   4  5  6  7   8  9  A  B   C  D  E
>> F
>> */^M
>>  /* 0 */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
>> -1,-1,-1,-1,^M
>>  /* 1 */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
>>
>
> 
>
> On _ARM_ (actually build failure seems to be on ARM) char is _unsigned_
> by default, so converting (int)-1 to char on ARM is narrowing conversion
> and C++11 forbids this on list-initialization.
>

Yes, I forgot to mention this was an ARM failure, i686 and x86_64 builds
will complete.


> You can do this when you explicitly cast, like
>  const char HEX2DEC[256] = { (char)-1, . }


I almost tried that but thought there might be a better way, I guess not...

Thanks,
Richard
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Re: openCOLLADA: Help with GCC6 narrowing conversion

[Mamoru TASAKA]

Richard Shaw wrote on 02/15/2016 11:34 PM:

Can someone point me in the right direction? My package openCOLLADA is
FTBFS in rawhide with the following (repeating) error:

/builddir/build/BUILD/OpenCOLLADA-3335ac164e68b2512a40914b14c74db260e6ff7d/COLLADABaseUtils/src/COLLADABUURI.cpp:57:2:
error: narrowing conversion of '-1' from 'int' to 'char' inside { }
[-Wnarrowing]
   };

I tried using the gcc6 porting guide but I'm not qutie enough of a
programmer to understand how to apply it in this case. The offending code
is:

 const char HEX2DEC[256] = ^M
 {^M
 /*   0  1  2  3   4  5  6  7   8  9  A  B   C  D  E  F
*/^M
 /* 0 */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-1,-1,-1,-1,^M
 /* 1 */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,




On _ARM_ (actually build failure seems to be on ARM) char is _unsigned_
by default, so converting (int)-1 to char on ARM is narrowing conversion
and C++11 forbids this on list-initialization.

You can do this when you explicitly cast, like
 const char HEX2DEC[256] = { (char)-1, . }

Regards,
Mamoru

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openCOLLADA: Help with GCC6 narrowing conversion

[Richard Shaw]

Can someone point me in the right direction? My package openCOLLADA is
FTBFS in rawhide with the following (repeating) error:

/builddir/build/BUILD/OpenCOLLADA-3335ac164e68b2512a40914b14c74db260e6ff7d/COLLADABaseUtils/src/COLLADABUURI.cpp:57:2:
error: narrowing conversion of '-1' from 'int' to 'char' inside { }
[-Wnarrowing]
  };

I tried using the gcc6 porting guide but I'm not qutie enough of a
programmer to understand how to apply it in this case. The offending code
is:

const char HEX2DEC[256] = ^M
{^M
/*   0  1  2  3   4  5  6  7   8  9  A  B   C  D  E  F
*/^M
/* 0 */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-1,-1,-1,-1,^M
/* 1 */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-1,-1,-1,-1,^M
/* 2 */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-1,-1,-1,-1,^M
/* 3 */  0, 1, 2, 3,  4, 5, 6, 7,  8, 9,-1,-1,
-1,-1,-1,-1,^M
^M
/* 4 */ -1,10,11,12, 13,14,15,-1, -1,-1,-1,-1,
-1,-1,-1,-1,^M
/* 5 */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-1,-1,-1,-1,^M
/* 6 */ -1,10,11,12, 13,14,15,-1, -1,-1,-1,-1,
-1,-1,-1,-1,^M
/* 7 */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-1,-1,-1,-1,^M
^M
/* 8 */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-1,-1,-1,-1,^M
/* 9 */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-1,-1,-1,-1,^M
/* A */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-1,-1,-1,-1,^M
/* B */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-1,-1,-1,-1,^M
^M
/* C */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-1,-1,-1,-1,^M
/* D */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-1,-1,-1,-1,^M
/* E */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-1,-1,-1,-1,^M
/* F */ -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1^M
};^M

Thanks,
Richard
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