Bug 38849 - ICE in fold_convert with C_F_POINTER and C binding
ICE in fold_convert with C_F_POINTER and C binding
Status: RESOLVED FIXED
Product: gcc
Classification: Unclassified
Component: fortran
unknown
: P3 normal
: ---
Assigned To: Not yet assigned to anyone
: ice-on-invalid-code
Depends on:
Blocks: 32630
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Reported: 2009-01-14 20:42 UTC by Daniel Kraft
Modified: 2013-01-15 21:34 UTC (History)
4 users (show)

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Host:
Target:
Build:
Known to work:
Known to fail: 4.3.2, 4.4.0, 4.5.1, 4.6.0
Last reconfirmed: 2009-10-07 14:09:36


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Description Daniel Kraft 2009-01-14 20:42:56 UTC
This program gives an ICE when compiled with gfortran 4.4 trunk:

FUNCTION myfortran_error ()
  USE ISO_C_BINDING
  IMPLICIT NONE
  CHARACTER(LEN=5) :: myfortran_error
  CHARACTER(KIND=C_CHAR, LEN=5), POINTER :: chararr
  TYPE(C_PTR) :: c_str

  c_str = C_NULL_PTR
  CALL C_F_POINTER (c_str, chararr)

  myfortran_error(1:1) = chararr(1)
END FUNCTION myfortran_error

bash-3.2# gfortran-dev reduced.f03 
reduced.f03: In function 'myfortran_error':
reduced.f03:8: internal compiler error: in fold_convert, at fold-const.c:2649
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.

gfortran 4.3 compiles it but fails with an undefined reference to `chararr_'.  Actually I'm not proficient with C binding, so I would not bet the code above is legal or doing "correct" things with the pointers... However, it should not ICE.
Comment 1 Mikael Morin 2009-01-24 20:36:57 UTC
Confirmed.

  myfortran_error(1:1) = chararr(1)

gfc_match_rvalue can't find a proper substring reference for chararr. 
Thus as  chararr's flavor is FL_UNKNOWN, gfc_match_rvalue tries to guess its type
and after some tests defaults to a function call. Then, as chararr is registered as a function it fails in the middle end when trying to convert a pointer type to a function type.

This is not a regression as the link error from 4.3 tells us (I think) that chararr went through the middle-end as a function. 

I think the correct syntax is:
  myfortran_error(1:1) = chararr(1:1)
Comment 2 Daniel Kraft 2009-10-07 14:09:35 UTC
This is still happening with current gfortran trunk, though the ICE is now in

[/tmp]# gfortran-dev test.f90 
test.f90: In function 'myfortran_error':
test.f90:8:0: internal compiler error: in fold_convert_loc, at fold-const.c:2789
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.

I will work on this.
Comment 3 Daniel Kraft 2009-10-07 14:12:35 UTC
As another note, I already did the mistake of indexing a string as str(n) instead of str(n:n) for single characters multiple times; and IIRC there's not much useful a diagnostic in any case, so maybe I can improve there as well.
Comment 4 Daniel Franke 2010-05-19 16:57:26 UTC
$ gfortran-4.5  pr38849.f90 
pr38849.f90: In function 'MAIN__':
pr38849.f90:9:0: internal compiler error: in gimplify_expr, at gimplify.c:7346

$ gfortran-svn  pr38849.f90 
gimplification failed:
chararr <addr_expr 0xb77a43b8
    type <pointer_type 0xb77a3c00
        type <function_type 0xb77a3ba0 type <void_type 0xb7729780 void>
            QI
            size <integer_cst 0xb77190f0 constant 8>
            unit size <integer_cst 0xb7719108 constant 1>
            align 8 symtab 0 alias set -1 canonical type 0xb77a3ba0
            arg-types <tree_list 0xb779ec60 value <reference_type 0xb77a3b40>
                chain <tree_list 0xb779ec78 value <integer_type 0xb77292a0 integer(kind=4)>
                    chain <tree_list 0xb779ec90 value <void_type 0xb7729780 void>>>>
            pointer_to_this <pointer_type 0xb77a3c00>>
        unsigned SI
        size <integer_cst 0xb7719240 constant 32>
        unit size <integer_cst 0xb7719078 constant 4>
        align 32 symtab 0 alias set -1 canonical type 0xb77a3c00>
    constant
    arg 0 <function_decl 0xb77a2c00 chararr type <function_type 0xb77a3ba0>
        public external QI file pr38849.f90 line 5 col 0 align 8
        chain <function_decl 0xb77a2b00 MAIN__ type <function_type 0xb774d060>
            used static QI file pr38849.f90 line 2 col 0 align 8 initial <block 0xb7727104> result <result_decl 0xb7722348 D.1499>
            (mem:QI (symbol_ref:SI ("MAIN__") [flags 0x3] <function_decl 0xb77a2b00 MAIN__>) [0 S1 A8])
            struct-function 0xb772239c chain <function_decl 0xb77a2a80 _gfortran_st_set_nml_var_dim>>>>
pr38849.f90: In function 'MAIN__':
pr38849.f90:9:0: internal compiler error: gimplification failed

$ gfortran-svn -v
gcc version 4.6.0 20100518 (experimental) (GCC)
Comment 5 janus 2012-04-26 11:49:14 UTC
With gfortran 4.6.3 and later I get:


  myfortran_error(1:1) = chararr(1)
                         1
Error: The pointer object 'chararr' at (1) must have an explicit function interface or be declared as array



The error message is not extremely clear about what is wrong, but at least there is no ICE any more. Is it worth to improve the error message, or should we just close this one?
Comment 6 Mikael Morin 2013-01-15 21:34:10 UTC
(In reply to comment #5)
> The error message is not extremely clear about what is wrong, but at least
> there is no ICE any more. Is it worth to improve the error message, or should
> we just close this one?

Let's close.