Question & Answer
Question
The following XL Fortran program does not perform as expected. Why is that?
----- testpg.f ----
[]
program testpg
call abc ($10,1)
write (6,*) ' should not drop thru CALL ABC ($10,1)'
stop 'testpg 1'
end
subroutine abc (*,in)
if (in .eq. 0) then
return
else
return 1
end if
end
[]
---end of testpg.f ----
> xlf testpg.f
** testpg === End of Compilation 1 ===
** abc === End of Compilation 2 ===
1501-510 Compilation successful for file testpg.f.
> ./a.out
should not drop thru CALL ABC ($10,1)
Answer
Some non-XL Fortran compilers interpret dollar ($) syntax as an alternate return specifier. XL Fortran interprets dollar syntax as part of a variable name, so that XL Fortran treats "$123" as a variable name. Both interpretations of dollar syntax are not standards compliant.
In the testcase testpg.f, the CALL statement is interpreted as passing the variable "$10" and the constant "1" to the subroutine "abc". However, the subroutine "abc" is expecting that the dummy arguments are an alternate return specifier and a variable of integer type.
On AIX, the -qextchk option can assist in diagnosing this problem through the "type mismatch" message at link-time.
> xlf -qextchk testpg.f
** testpg === End of Compilation 1 ===
** abc === End of Compilation 2 ===
1501-510 Compilation successful for file testpg.f.
ld: 0711-197 ERROR: Type mismatches for symbol: .abc
ld: 0711-345 Use the -bloadmap or -bnoquiet option to obtain more information.
The -qlanglvl option can also help you identify non-standards compliant variables that begin with a dollar sign. For example:
>xlf -qlanglvl=90std testpg.f
"testpg.f", line 2.17: 1518-095 (L) $ is not permitted in a symbolic name in Fortran 95 or Fortran 90.
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Document Information
Modified date:
24 February 2022
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swg21187892