$ gfortran -g gfortran.dg/class_to_type_1.f03
$ MALLOC_PERTURB_= ./a.out
$ MALLOC_PERTURB_=33 ./a.out
A fatal error occurred! Backtrace for this error:
#6 0x400929 in __copy_MAIN___T2 at class_to_type_1.f03:5
#7 0x4013D1 in MAIN__ at class_to_type_1.f03:17
That's a typical sign for code which requires that "malloc" returns '\0'-set memory, i.e. gfortran generates code which uses an uninitialized variable.
(In reply to comment #0)
> $ gfortran -g gfortran.dg/class_to_type_1.f03
> $ MALLOC_PERTURB_= ./a.out
> $ MALLOC_PERTURB_=33 ./a.out
> A fatal error occurred! Backtrace for this error:
> #6 0x400929 in __copy_MAIN___T2 at class_to_type_1.f03:5
> #7 0x4013D1 in MAIN__ at class_to_type_1.f03:17
> That's a typical sign for code which requires that "malloc" returns '\0'-set
> memory, i.e. gfortran generates code which uses an uninitialized variable.
I cannot reproduce this on x86_64/FC9. Nor can I see anything obvious in the code.... on the other hand, there is a lot of it!
I'll try on my Debian equipped laptop tomorrow.
The problem is the following, for:
allocate(t2 :: x(10))
x._data.data = (void * restrict) __builtin_malloc (640);
I had now expected that one would do:
for (i = 1; i <= 10; i++)
__builtin_memcpy ((void *) x._data,
(void *) &__vtab_MAIN___T2._def_init,
However, the current code does:
struct t2 D.1921;
struct t2 t2.2;
struct t[0:] * restrict D.1918;
D.1918 = (struct t[0:] * restrict) x._data.data;
D.1919 = x._data.offset;
t2.2.t.b.data = 0B;
t2.2.z = __complex__ (3.2999999523162841796875e+0, 4.400000095367431640625e+0);
D.1921 = t2.2;
So far so good. That's the same as __vtab_MAIN___T2._def_init. Disadvantage: Code duplication. Advantage: The information in in the same file (translation unit).
However, instead of just doing a __builtin_memcpy in a loop, one calls:
(struct t *) D.1918
+ (sizetype) ((S.3 + D.1919) * (integer(kind=8))
This has several disadvantages: First, makes the advantage of having all data in the same translation unit void as one calls a function, located in another translation unit. It is also much slower as _copy does many checks which we know shouldn't matter. For MOLD= or a type-spec we know that the destination does not have allocated allocatable components.
However, I do now understand why one needs for SOURCE= to memset the source to NULL - at least as long _copy not only copies the data but also frees it. The latter could be also left to _free. - Actually, I am in favour of separating _copy and _free. As this issue shows, there are cases where one does not want to combine them, leading to work around actions (memset). I think only for polymorphic assignment, one needs _free + _copy, for allocate with SOURCE= a _copy should be enough.
The reason for the crash is:
__copy_MAIN___T2 (struct t2 & restrict src, struct t2 & restrict dst)
if (dst->t.b.data != 0B)
__builtin_free ((void *) dst->t.b.data);
where dst == x._data.data, where the latter and thus also x._data.data->t.b.data is filled with random memory.
> However, I do now understand why one needs for SOURCE= to memset the source to
> NULL - at least as long _copy not only copies the data but also frees it. The
> latter could be also left to _free. - Actually, I am in favour of separating
> _copy and _free. As this issue shows, there are cases where one does not want
> to combine them, leading to work around actions (memset). I think only for
> polymorphic assignment, one needs _free + _copy, for allocate with SOURCE= a
> _copy should be enough.
The memset came about for similar reasons with class objects with
allocatable components. I had missed this wrinkle with the testcase.
My inclination is to restire the memset and keep the PR open.
I am am trying to clear up some issues of functionality, starting with
the failure of a%disp() to scalarize properly in class_array_3.f03.
Then I have mind to understand the failure of vector indexing in
gfc_trans_call and finally to deal with class array components and
class array subreferences. After the tidy up :-)
(In reply to comment #3)
> The memset came about for similar reasons with class objects with
> allocatable components. I had missed this wrinkle with the testcase.
> My inclination is to restire the memset and keep the PR open.
I am fine with it, but state in the comment above the memset that it is needed as _copy tries to free the allocatable components of "dest" - that makes clear why the memset is need for our implementation.
On hppa2.0w-hp-hpux11.11, the test fails but the backtrace also fails:
A fatal error occurred! Backtrace for this error:#0 0xC1B39FE3FAIL: gfortran.dg/class_to_type_1.f03 -O0 execution test
Date: Mon Jan 2 12:46:08 2012
New Revision: 182796
2012-01-02 Paul Thomas <email@example.com>
* trans-array.c (gfc_array_allocate): Null allocated memory of
newly allocted class arrays.
* interface.c(build_compcall_for_operator): Add a type to the
* trans-expr.c (conv_base_obj_fcn_val): New function.
(gfc_conv_procedure_call): Use base_expr to detect non-variable
base objects and, ensuring that there is a temporary variable,
build up the typebound call using conv_base_obj_fcn_val.
(gfc_trans_class_assign): Pick out class procedure pointer
assignments and do the assignment with no further prcessing.
gfc_trans_class_assign): Move to top of file.
* gfortran.h : Add 'base_expr' field to gfc_expr.
* resolve.c (get_declared_from_expr): Add 'types' argument to
switch checking of derived types on or off.
(resolve_typebound_generic_call): Set the new argument.
Set 'types' argument for get_declared_from_expr appropriately.
Identify base expression, if not a variable, in the argument
list of class valued calls. Assign it to the 'base_expr' field
of the final expression. Strip away all references after the
last class reference.
2012-01-02 Paul Thomas <firstname.lastname@example.org>
* gfortran.dg/typebound_operator_7.f03: New.
* gfortran.dg/typebound_operator_8.f03: New.
Fixed on trunk.
Thanks for the reports