Re: [PATCH 0/3] yacc: compute the best type for the state number

[Paul Eggert]

On 10/6/19 4:57 AM, Akim Demaille wrote:

> With the appended commits, the CI is green again, and I was able to push my 
> other changes.

Thanks. I reproduced the GCC 4.8 problem and installed a patch that works around 
it without casts (see first attached patch).


>          "\"".c:1102:41: error: implicit conversion loses integer precision: 
> 'long' to 'int' [-Werror,-Wshorten-64-to-32]
>                YYPTRDIFF_T yysize = yyssp - yyss + 1;
>                            ~~~~~~   ~~~~~~~~~~~~~^~~

This is a more serious problem, as it says that YYPTRDIFF_T is 'int' on a 
platform where ptrdiff_t is really 'long', which means Bison-generated parsers 
could mishandle vary large inputs. That is, the clang diagnostic is pointing out 
an (unlikely) bug, and is not a false alarm.

Although I installed the second attached patch which I hope works around the 
immediate problem, a better fix is needed here. With a C++ compiler, the 
definition of YYPTRDIFF_T should not be a guess at 'int' or 'long'; it should be 
the proper C++ type for pointer subtraction results. When you find the time I'd 
be interested to see the proper portable C++ magic to do that.

0001-Work-around-GCC-4.8-false-alarms-without-casts.patch
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0002-Port-better-to-C-platforms.patch
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