Обсуждение: AW: Re: RELEASE STOPPER? nonportable int64 constants in pg_crc.c

> > Recent changes in pg_crc.c (64 bit CRC) introduced non
> portable constants of the form:
>
> >  -c -o pg_crc.o pg_crc.c
> >       287 |         0x0000000000000000, 0x42F0E1EBA9EA3693,
> >             ............................a..................
> > a - 1506-207 (W) Integer constant 0x42F0E1EBA9EA3693 out of range.
>
> Please observe that this is a warning, not an error.  Your proposed
> fix is considerably worse than the disease, because it will break on
> compilers that do not recognize "LL" constants, to say nothing of
> machines where L is correct and LL is some yet wider datatype.
>
> I'm aware that some compilers will produce warnings about these
> constants, but there should not be any that fail completely, since
> (a) we won't be compiling this code unless we've proven that the
> compiler supports a 64-bit-int datatype, and

Unfortunately configure does not check the use of 64 bit integer
constants. A little check on AIX shows, that it indeed DOES NOT work !!!!!

$ ./a.out
hex: 0x012345670ABCDEF0LL==12345670abcdef0, 0x012345670ABCDEF0==abcdef02ff22ff8

> (b) the C standard
> forbids a compiler from requiring width suffixes (cf. 6.4.4.1 in C99).

Maybe that standard is somewhat too recent to rely upon 100%.

> I don't think it's a good tradeoff to risk breaking some platforms in
> order to suppress warnings from overly anal-retentive compilers.

I really do expect other compilers to break on this too. Thus I think
a workaround is needed. As it stands the code does not compute
a valid CRC64 on all platforms.

Do you want me to supply an AIX specific patch with #if defined (_AIX) ?

Andreas

Zeugswetter Andreas SB  <ZeugswetterA@wien.spardat.at> writes:
>> I'm aware that some compilers will produce warnings about these
>> constants, but there should not be any that fail completely, since
>> (a) we won't be compiling this code unless we've proven that the
>> compiler supports a 64-bit-int datatype, and 

> Unfortunately configure does not check the use of 64 bit integer 
> constants. A little check on AIX shows, that it indeed DOES NOT work !!!!!

Grumble...

>> (b) the C standard
>> forbids a compiler from requiring width suffixes (cf. 6.4.4.1 in C99).

> Maybe that standard is somewhat too recent to rely upon 100%.

ANSI C says the same thing, although of course it only discusses int and
long.  But the spec has always been clear that the implied type of an
integer constant is whatever it takes to hold it; you do not need an
explicit "L" suffix to make a valid constant.  AIX's compiler is broken.

> Do you want me to supply an AIX specific patch with #if defined (_AIX) ?

I'll do something about it.  Would you check to see whether a macro like
#define SIXTYFOUR(x)  x##LL
works?
        regards, tom lane