Re: [Bug-apl] Warnings when compiling with -Wall

[Juergen Sauermann]

Hi,

the reason is that gcc does not allow unions with members that have constructors.
It used to be allowed earlier, but not anymore (and I miss it).

/// Jürgen


On 04/10/2014 05:15 AM, Elias Mårtenson wrote:

I'm having some problems with warnings emitted when using -Wstrict-aliasing.

One of the cases where this warning is emitted is when a pointer to some value is cast to another type of pointer and then dereferenced. This happens, for example, in the RANK_LXB structure, as well as the VALUE_P macro in SharedValuePointer.hh.

Can you explain why the _sh_B_low is declared like this:

  char _sh_B_low [ sizeof(Shape) ];      ///< low dimensions of B

instead of simply:

  Shape _sh_B_low;

Regards,

Elias

On 10 April 2014 10:58, Elias Mårtenson <address@hidden> wrote:

I fully agree with you. I also feel that the designers of Java did the right thing in eliminating unsigned int.

The problem in this case is that size_t is declared as unsigned long, so that's where the unsigned comes from.

On 10 April 2014 00:21, Juergen Sauermann <address@hidden> wrote:

Hi Elias,

yes, please. One word of warning, though:

When I was young I tried to be precise in using unsigned for items that could not be negative,
These days I would rather use signed even if I knew they can't be negative.

The reason is that differences of unsigned are signed (or wrong if declared unsigned) and that
can produce wrong results without a warning. In contrast signed arithmetic is always correct
(unless you overflow which is almost never the case).

The only case where unsigned is beneficial is things like ((unsigned)a < b) to have a single comparison instead of
a >= 0 && a < b or so.

/// Jürgen

On 04/09/2014 03:56 PM, Elias Mårtenson wrote:

There are plenty of warnings when compiling with the -Wall flag. One example is the following error (it's included from my code, but the error is in UCS_string.hh):

c++ -Wall -fPIC -g -I/home/elias/src/apl/src   -c -o ResultValue.o ResultValue.cc

In file included from /home/elias/src/apl/src/Error.hh:27:0,

                 from /home/elias/src/apl/src/Token.hh:29,

                 from /home/elias/src/apl/src/Parser.hh:24,

                 from /home/elias/src/apl/src/Cell.hh:26,

                 from ResultValue.hh:24,

                 from ResultValue.cc:21:

/home/elias/src/apl/src/UCS_string.hh: In member function ‘bool UCS_string::all_zeroes()’:

/home/elias/src/apl/src/UCS_string.hh:140:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]

       { for (size_t s = 0; s < size(); ++s)

                                     ^

I want to fix these, but in many cases the solution is not entirely clear. In the above case, for example, you could either do a static_cast<size_t>(size()), or one could change the return value of the size() function to size_t.

There are plenty of others. Would you like me to send patches for the obvious ones?

Regards,

Elias