[flang] Runtime failure on list-directed I/O

[DanielCChen]

Consider the following code:

      implicit none

      integer, parameter :: in = 11

      real(4) :: nanq_pos, nanq_neg, nans_pos, nans_neg, inf_pos, inf_neg

      character(3) :: c1, c2

      open(in,  file='modeMixNaNInfIO001.dat', action='read')

      ! reset variables
      nanq_pos = 0.0; nanq_neg = 0.0; nans_pos = 0.0; nans_neg = 0.0
      inf_pos  = 0.0; inf_neg  = 0.0
      c1 = 'xxx'
      c2 = 'xxx'

      open(in, delim='quote', blank='zero', sign='plus')
      read(in, *) nanq_pos, c1, nanq_neg, c2, nans_pos, nans_neg,    &
     &            inf_pos, inf_neg

      close(in)

      end

modeMixNaNInfIO001.dat contains

+nan(q) xlf -nan(q) 'ibm' +nan(s) -nan(s) +inf -Inf
+nan "xlf" -nan() ibm +nan(s) -nan(s) +infinity -Infinity
nan() "xlf" -nan ibm +nan(s) -nan(s) +infinity -Infinity

Flang failed at the execution as

> a.out

fatal Fortran runtime error(t.f:23): invalid character (0x28) after list-directed input value, at column 5 in record 1
IOT/Abort trap(coredump)

It seems it complains about the ( in the record.

If I remove all the "(*)" from the modeMixNaNInfIO001.dat based on Flang's runtime error message, Flang works fine.

Both gfortran and XLF executes the original code successfully.

[llvmbot]

@llvm/issue-subscribers-flang-runtime

Author: Daniel Chen (DanielCChen)

Consider the following code: ``` implicit none

  integer, parameter :: in = 11

  real(4) :: nanq_pos, nanq_neg, nans_pos, nans_neg, inf_pos, inf_neg

  character(3) :: c1, c2

  open(in,  file='modeMixNaNInfIO001.dat', action='read')

  ! reset variables
  nanq_pos = 0.0; nanq_neg = 0.0; nans_pos = 0.0; nans_neg = 0.0
  inf_pos  = 0.0; inf_neg  = 0.0
  c1 = 'xxx'
  c2 = 'xxx'

  open(in, delim='quote', blank='zero', sign='plus')
  read(in, *) nanq_pos, c1, nanq_neg, c2, nans_pos, nans_neg,    &
 &            inf_pos, inf_neg

  close(in)

  end

`modeMixNaNInfIO001.dat` contains

+nan(q) xlf -nan(q) 'ibm' +nan(s) -nan(s) +inf -Inf
+nan "xlf" -nan() ibm +nan(s) -nan(s) +infinity -Infinity
nan() "xlf" -nan ibm +nan(s) -nan(s) +infinity -Infinity

Flang failed at the execution as

> a.out

fatal Fortran runtime error(t.f:23): invalid character (0x28) after list-directed input value, at column 5 in record 1
IOT/Abort trap(coredump)

It seems it complains about the `(` in the record.

If I remove all the "(*)" from the `modeMixNaNInfIO001.dat` based on Flang's runtime error message, Flang works fine.

Both gfortran and XLF executes the original code successfully.
</details>

[DanielCChen]

It seems the standard allows optional things for the input field of IEEE exceptional specification as:

An input field that is an IEEE exceptional specification consists of optional blanks, followed by either
 • an optional sign, followed by the string ’INF’ or the string ’INFINITY’, or
 • an optional sign, followed by the string ’NAN’, optionally followed by zero or more alphanumeric characters
 enclosed in parentheses,
optionally followed by blanks.

XLF has NaN(S) representing IEEE_SIGNALING_NAN and NaN(Q) for IEEE_QUIET_NAN.

Flang doesn't seem support this.

[DanielCChen]

I have added the output part of the test in the following updated test case.
Even though Flang is able to parse the NaN(Q) after PR #149606 , but it doesn't write it back to the output file, which seems a bit inconsistent.

      implicit none

      integer, parameter :: in = 11, out = 12

      real(4) :: nanq_pos, nanq_neg, nans_pos, nans_neg, inf_pos, inf_neg

      character(3) :: c1, c2

      open(in,  file='modeMixNaNInfIO001.dat', action='read')
      open(out, file='modeMixNaNInfIO001.out', action='write')

      ! reset variables
      nanq_pos = 0.0; nanq_neg = 0.0; nans_pos = 0.0; nans_neg = 0.0
      inf_pos  = 0.0; inf_neg  = 0.0
      c1 = 'xxx'
      c2 = 'xxx'

      open(in, delim='quote', blank='zero', sign='plus')
      read(in, *) nanq_pos, c1, nanq_neg, c2, nans_pos, nans_neg,    &
     &            inf_pos, inf_neg

      open(out, delim='quote', blank='zero', sign='plus')
      write(out, *) nanq_pos, c1, nanq_neg, c2, nans_pos,            &
     &              nans_neg, inf_pos, inf_neg

      close(in)
      close(out)

      end

In modeMixNaNInfIO001.out, it has

NaN "xlf" NaN "ibm" NaN NaN +Inf -Inf

instead of

NaN(Q) "xlf" NaN(Q) "ibm" NaN(S) NaN(S) +Inf -Inf

I saw the comment that Flang does not interpret the string, but just want to make sure this "inconsistency" in acceptable.

[klausler]

XLF is the only compiler I know of that emits anything more than "NaN'.

[DanielCChen]

@klausler
There is another variation of this issue that still fails with #149606

use, intrinsic :: ieee_arithmetic
real :: res
open(2,file='test.dat')
read(2,'(f20.2)') res
close(2)
end

When test.dat contains nan, it works fine.
However, if it contains nan(q), Flang failed as

> a.out

fatal Fortran runtime error(t.f:4): Bad real input data at column 5 of record 1
IOT/Abort trap(coredump)

If I change the real edit descriptor to f6.2 to match the exact length of the string, it works fine.

[DanielCChen]

The latest patch of #149606 fixed the variation.