[Bug gcov-profile/78792] New: gfortran + gcov confused by #line directive

["patrick.seewald at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78792

            Bug ID: 78792
           Summary: gfortran + gcov confused by #line directive
           Product: gcc
           Version: 6.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: gcov-profile
          Assignee: unassigned at gcc dot gnu.org
          Reporter: patrick.seewald at gmail dot com
  Target Milestone: ---

$ cat example.in
PROGRAM example
PRINT *, "example"
END PROGRAM

$ cat example.f90
#line 1 "example.in"
PROGRAM example
PRINT *, "example"
END PROGRAM

$ gfortran -fprofile-arcs -ftest-coverage -cpp example.f90 -o example.out
$ ./example.out
$ gcov example.in
File 'example.f90'
Lines executed:100.00% of 3
Creating 'example.f90.gcov'

$ cat example.f90.gcov
        -:    0:Source:example.f90
        -:    0:Graph:example.gcno
        -:    0:Data:example.gcda
        -:    0:Runs:1
        -:    0:Programs:1
        1:    1:#line 1 "example.in"
        1:    2:PROGRAM example
        2:    3:PRINT *, "example"
        -:    4:END PROGRAM


The output example.f90.gcov refers to example.f90 instead of example.in. Note
that the line statistics are shifted by one line, I guess they really refer to
the line numbers of example.in.

For some reason, the coverage report is correct if an #include statement is
present:

$ touch inc
$ cat example2.in
#include "inc"
PROGRAM example2
PRINT *, "example2"
END PROGRAM

$ cat example2.f90
#line 1 "example2.in"
#include "inc"
PROGRAM example2
PRINT *, "example2"
END PROGRAM

$ gfortran -fprofile-arcs -ftest-coverage -cpp example2.f90 -o example2.out
$ ./example2.out
$ gcov example2.in
File 'example2.in'
Lines executed:100.00% of 3
Creating 'example2.in.gcov'

$ cat example2.in.gcov
        -:    0:Source:example2.in
        -:    0:Graph:example2.gcno
        -:    0:Data:example2.gcda
        -:    0:Runs:1
        -:    0:Programs:1
        -:    1:#include "inc"
        1:    2:PROGRAM example2
        1:    3:PRINT *, "example2"
        2:    4:END PROGRAM