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From: "jvdelisle at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libfortran/113897] New: Consecutive tab edits in format are not
 processed correctly.
Date: Tue, 13 Feb 2024 03:31:35 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113897

            Bug ID: 113897
           Summary: Consecutive tab edits in format are not processed
                    correctly.
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libfortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jvdelisle at gcc dot gnu.org
  Target Milestone: ---

This issue found while working on pr109358.

program tabs
  implicit none
  integer :: fd
  open(newunit=3Dfd, file=3D"test.txt", form=3D"formatted")
  write(fd, "(a)") "12345678901234567890123456789"
  write(fd, "(i4, t25, t2, i4.4)") 1234, 0123
  close(fd)
end program tabs

With gfortran gcc 10.4.1 20230121 (GCC)

$ gfc10 -static -o tabs.x tabs.f90
$ ./tabs.x=20
$ cat test.txt=20
12345678901234567890123456789
1234                0123

It seems to me this should be:

10123

Even though it is nonsensical to do this, it probably is valid. I will check
the standards.=