[Bug?] Internal compiler error concerning unlimited polymorphic pointer...

[Matthew Neilson]

Dear all,

I am receiving an internal compiler error with what I believe should be a legitimate piece of code. I decided against filing this directly with bugzilla, since the GCC wiki states that it is also acceptable to ask questions here on the gfortran mailing list (especially for those who, like me, are unfamiliar with using bugzilla).

I have attached some annotated sample code ('test.f90') that produces the error in question. I have minimised the code to the best of my ability, whilst retaining my desired code structure. The attached file contains three inline modules:

Module X, which defines types,
Module Y, which defines common pointers, and
Module Z, which contains subroutines.

The compiler seems to have trouble with the subroutine that I've named 'BUG' (lines 37-50); more specifically, the compiler appears to be complaining about line 48 (which I have labelled line "C"). The 'BUG' subroutine calls the subroutine named 'NEXT' to associate the 'e' pointer with a piece of preallocated memory, and then points the unlimited polymorphic 'e%info' variable to the piece of memory associated with the pointer 'p'. Attempting to compile the code as-is produces the following output:

### Beginning of Terminal output ###

matt$ gfortran -v -save-temps -o test test.f90 
Driving: gfortran -mmacosx-version-min=10.10.1 -v -save-temps -o test test.f90 -l gfortran -shared-libgcc
Using built-in specs.
COLLECT_GCC=gfortran
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/x86_64-apple-darwin14.0.0/4.9.2/lto-wrapper
Target: x86_64-apple-darwin14.0.0
Configured with: ../gcc-4.9-20141029/configure --enable-languages=c++,fortran
Thread model: posix
gcc version 4.9.2 20141029 (prerelease) (GCC) 
COLLECT_GCC_OPTIONS='-mmacosx-version-min=10.10.1' '-v' '-save-temps' '-o' 'test' '-shared-libgcc' '-mtune=core2'
 /usr/local/libexec/gcc/x86_64-apple-darwin14.0.0/4.9.2/f951 test.f90 -fPIC -quiet -dumpbase test.f90 -mmacosx-version-min=10.10.1 -mtune=core2 -auxbase test -version -fintrinsic-modules-path /usr/local/lib/gcc/x86_64-apple-darwin14.0.0/4.9.2/finclude -o test.s
GNU Fortran (GCC) version 4.9.2 20141029 (prerelease) (x86_64-apple-darwin14.0.0)
	compiled by GNU C version 4.9.2 20141029 (prerelease), GMP version 6.0.0, MPFR version 3.1.2-p10, MPC version 1.0.2
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
GNU Fortran (GCC) version 4.9.2 20141029 (prerelease) (x86_64-apple-darwin14.0.0)
	compiled by GNU C version 4.9.2 20141029 (prerelease), GMP version 6.0.0, MPFR version 3.1.2-p10, MPC version 1.0.2
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
test.f90: In function ‘bug’:
test.f90:48:0: internal compiler error: in gfc_conv_component_ref, at fortran/trans-expr.c:1660
       e%info => p      ! line "C"
 ^

test.f90:48:0: internal compiler error: Abort trap: 6
gfortran: internal compiler error: Abort trap: 6 (program f951)
Abort trap: 6

### End of Terminal output ###

Oddly enough, the code compiles without error if I comment-out the call to 'NEXT' (line 42, which I've labelled line "A") and uncomment lines 43-45 (which I've labelled lines "B_1", "B_2", and "B_3"), even though the 'NEXT' subroutine contains *exactly* the same content as lines 43-45.

Am I correct in thinking that this is a bug in the compiler that needs to be fixed?

Best wishes,

-Matt

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