https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102145
Bug ID: 102145
Summary: TKR mismatches with -pedantic:
-fallow-argument-mismatch does not degrade errors to
warnings
Product: gcc
Version: 11.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: ripero84 at gmail dot com
Target Milestone: ---
In the presence of -pedantic, -fallow-argument-mismatch fails to degrade the
mismatch errors to warnings:
$ cat pedt.f90
MODULE M
IMPLICIT NONE
EXTERNAL :: X
CONTAINS
SUBROUTINE S(A)
COMPLEX :: A(*)
CALL X(A)
END
SUBROUTINE T(A)
REAL :: A(*)
CALL X(A)
END
END
$ gfortran pedt.f90 -c -o pedt.o -fallow-argument-mismatch # Expected warning
pedt.f90:8:11:
8 | CALL X(A)
| 1
......
13 | CALL X(A)
| 2
Warning: Type mismatch between actual argument at (1) and actual argument at
(2) (COMPLEX(4)/REAL(4)).
$ gfortran pedt.f90 -c -o pedt.o -fallow-argument-mismatch -pedantic #
Unexpected error
pedt.f90:8:11:
8 | CALL X(A)
| 1
......
13 | CALL X(A)
| 2
Error: Type mismatch between actual argument at (1) and actual argument at (2)
(COMPLEX(4)/REAL(4)).
This is:
- undocumented; and
- unexpected, since it effectively means that by adding -pedantic to a
compilation line that already contains -fallow-argument-mismatch, mismatch
warnings are upgraded to errors, despite -pedantic is only supposed to issue
warnings.
It seems that GCC developers have known for years that -pedantic may change
warnings to errors in the absence of error-raising flags
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=30929#c9), but it is still
unclear to me whether this is undocumented or wrong behaviour.
Note that there is evidence that -fallow-argument-mismatch is actually being
processed: if the compiler finds multiple mismatches involving a given
argument, it succeeds in only reporting one of them (as an error, not as the
expected warning).
I am seeking clarification about whether this is a bug (the combination of
-pedantic -fallow-argument-mismatch flags should work differently / be
forbidden), a documentation bug (in which case I would appreciate an
explanation of the logic behind this, and an update to the documentation), or
both, and I would be grateful for the fix(/es).
I am aware that -fallow-argument-mismatch is a hack that should be avoided, but
since users still need it, its behaviour and documentation should be at least
consistent. Note that this issue has already been reported by some Fortran
codes: https://github.com/cp2k/cp2k/issues/1019,
https://gitlab.com/siesta-project/siesta/-/issues/130 .
This seems to affect all versions of gfortran since GCC 10. It would be nice
if any updates related to this were ported to the 10.x branch.
Thank you for your help.
