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[Bug fortran/33544] Spurious warning in TRANSFER intrinsic in Sept 24 snapshot of gfortran
- From: "sgk at troutmask dot apl dot washington dot edu" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 24 Sep 2007 19:59:37 -0000
- Subject: [Bug fortran/33544] Spurious warning in TRANSFER intrinsic in Sept 24 snapshot of gfortran
- References: <email@example.com/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #5 from sgk at troutmask dot apl dot washington dot edu 2007-09-24 19:59 -------
Subject: Re: Spurious warning in TRANSFER intrinsic in Sept 24 snapshot of
On Mon, Sep 24, 2007 at 07:17:54PM -0000, burnus at gcc dot gnu dot org wrote:
> ------- Comment #4 from burnus at gcc dot gnu dot org 2007-09-24 19:17 -------
> > We may want to hide the warning behind a -Wshort-transfer option
> > (or some other appropriate name).
> Maybe; I think having a warning by default would be more reasonable but it
> should be hideable.
I don't fell strongly either way, but I do agree one should be able to
turn off/on the warning.
> > Afterall, if a programmer wrote 'rft = transfer(' ', 0.0)',
> > then s/he probably meant it.
> I sincerely doubt that the programmer meant that this piece of code produces
> different results depending on the compiler and possibly some random value in
It may not produce random values each time (see below). Michael (a user)
did file a bug report, and knowing him for previous bug reports and posts
elsewhere on the net, I suspect he did intend the short transfer.
> For the given example, many compilers seem to initialize the result
> with zero; example:
> PROGRAM printd
> REAL :: rft
> rft = TRANSFER(' ', 0.0)
> print *, rft
> rft = TRANSFER(' '//achar(0)//achar(0)//achar(0), 0.0)
> print *, rft
> END PROGRAM printd
> The second transfer produces: 4.4841551E-44
> g95, ifort and openf95 seem to produce the same result also for the first
> gfortran, NAG f95 and sunf95 have, however, a different result every time.
> Thus, if one wants to argue that the programmer intended a certain value, I
> would argue that it is the one using a zero-padded SOURCE.
The programmer for whatever reason could be using rft as temporary storage.
Yes, I know it's a hypothetical situation, but the following is legal code
and should not give a warning.
rft = transfer(' ', 0.)
! print *, rft <-- Uncommenting may make this invalid code
c = transfer(rft, c)
if (c .eq. ' ') print *, 'space'
Note, if I uncomment the print statement, on x86_64-*-freebsd, it prints
a NaN every time I execute the program.