[Patch, fortran] PR31205 - aliased operator assignment produces wrong result

[Paul Richard Thomas]

:ADDPATCH fortran:

This one was 'fun'!  Neither aliased lhs and rhs in operator
assignments, nor INTENT(IN) actual arguments, aliased with an
INTENT(OUT) argument, would produce the correct result, if the
argument was a derived type with a default initializer.

The steps taken to fix this problem were:

(i) Generate a temporary for the rhs/INTENT(IN), using
gfc_get_parentheses.  This required a bit of improvement to this
function; resolving the argument and checking for references with
non-numeric expressions.  I believe that this latter will be
unnecessary when I complete the character patch (next week's task) and
will update accordingly.

(ii) Remove the initialization of derived types with a default
initializer from the caller to the callee.  The reasons for doing this
are discussed in the PR.  It has a gratifying effect on passing
derived types with allocatable components, in that the amount of
generated code goes down (see alloc_comp_basics_1.f90).

Note (i) involved what I believe is a misinterpretation of the
standard - see the comment and the relevant paragraph in the standard
(7.1.7.2).

The testcase is the reporter's.

Bootstrapped and regtested on x86_ia64/FC5 - OK for trunk?

Paul

2007-06-30  Paul Thomas  <pault@gcc.gnu.org>

	PR fortran/31205
	* trans-expr.c (gfc_conv_function_call): Remove the default
	initialization of intent(out) derived types.
	* symbol.c (gfc_lval_expr_from_sym): New function.
	* matchexp.c (gfc_get_parentheses): Rsolve argument expression
	and return argument, if it is not numeric and posseses a ref.
	* gfortran.h : Add prototype for gfc_lval_expr_from_sym.
	* resolve.c (has_default_initializer): Move higher up in file.
	(resolve_code): On detecting an interface assignment, check
	if the rhs and the lhs are the same symbol.  If this is so,
	enclose the rhs in parenetheses to generate a temporary and
	prevent any possible aliasing.
	(apply_default_init): Remove code making the lval and call
	gfc_lval_expr_from_sym instead.
	* trans-decl.c (gfc_trans_deferred_vars): Apply the a default
	initializer, if any, to an intent(out) derived type, using
	gfc_lval_expr_from_sym and gfc_trans_assignment.  Check if
	the dummy is present.


2007-06-30  Paul Thomas  <pault@gcc.gnu.org>

	PR fortran/31205
	* gfortran.dg/alloc_comp_basics_1.f90 : Restore number of
	"deallocates" to 24, since patch has code rid of much spurious
	code.
	* gfortran.dg/interface_assignment_1.f90 : New test.
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