https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94446
Bug ID: 94446 Summary: Bogus "type mismatch" with TYPE(c_ptr) and sizeof() Product: gcc Version: 10.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: fortran Assignee: unassigned at gcc dot gnu.org Reporter: abensonca at gcc dot gnu.org Target Milestone: --- The following causes a bogus "type mismatch" error with the current trunk (e899d4b71255b9ae096a7ecd31a61fc76f200019): $ cat file1.F90 module nrn use, intrinsic :: ISO_C_Binding type :: rgc private contains procedure :: st => rgcST end type rgc type, extends(rgc) :: rgcG private contains procedure :: st => rgcGST end type rgcG interface module subroutine rgcGST(s,gsf) class(rgcG), intent(inout) :: s type(c_ptr), intent(in ) :: gsf end subroutine rgcGST end interface contains subroutine rgcST(s,gsf) implicit none class(rgc), intent(inout) :: s type(c_ptr), intent(in ) :: gsf end subroutine rgcST end module nrn $ cat file2.F90 module gn use :: nrn type, public :: mt class (rgc), pointer :: rgc_ end type mt type, public :: tn type (mt), pointer :: ht contains end type tn contains subroutine tnc() type(tn) :: a write (0,*) sizeof(a) end subroutine tnc end module gn module eh use :: gn end module eh $ gfortran -v Using built-in specs. COLLECT_GCC=gfortran COLLECT_LTO_WRAPPER=/home/abenson/Galacticus/Tools/libexec/gcc/x86_64-pc-linux-gnu/10.0.1/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: ../gcc-git/configure --prefix=/home/abenson/Galacticus/Tools --enable-languages=c,c++,fortran --disable-multilib : (reconfigured) ../gcc-git/configure --prefix=/home/abenson/Galacticus/Tools --disable-multilib --enable-languages=c,c++,fortran,lto --no-create --no-recursion Thread model: posix Supported LTO compression algorithms: zlib gcc version 10.0.1 20200401 (experimental) (GCC) $ gfortran -c file1.F90 -o file1.o $ gfortran -c file2.F90 -o file2.o file2.F90:24:8: 24 | use :: gn | 1 Error: Argument mismatch for the overriding procedure 'st' at (1): Type mismatch in argument 'gsf' (TYPE(c_ptr)/INTEGER(8)) The error only occurs if the module in file1.F90 is compiled separately - if I combine file1.F90 and file2.F90 into a single file, that single file compiles without error. I haven't been able to reduce the testcase further, and figuring out the cause of the error has so far been beyond my ability. What I have found though is that in the nrn.mod module file created by compiling file.F90 all instances of symbol "gsf" are correctly given DERIVED type. But, in gn.mod created by compiling file2.F90 there are two instances of symbol "gsf", the first has DERIVED type, while the second has INTEGER type. So, it seems that the problem occurs at (or before) the creation of the gn.mod module file. Also, the use of the "sizeof()" intrinsic is necessary to trigger the bug.