[patch,fortran] PR33268 read ('(f3.3)'), a rejected due to the extra (...)

[Jerry DeLisle]

Hi Folks,

This patch provides for the "format" form of the READ and PRINT statements.  By 
"format" form I mean with no UNIT specified. The patch also rejects the WRITE 
statement with this form.  See section 9.5 of the F2003 Standard.

By example:

print('a'), 'Hello'       ! Invalid, missing parens inside format string
write(*,('(a)')) 'Hello'  ! Valid
write (*,'(f8.3)'), 3.141597  ! Extension, comma after the ')'
write ('(a)'), "invalid"  ! Invalid, "format" form not allowed for WRITE
print ('(a)'), "valid"    ! Valid, "format" form accepted
read ('(f3.3)')), a       ! Valid, "format form accepted

To accomplish this, I added a new expression pointer, extra_comma, to pass the 
io_kind and locus to gfc_resolve_dt.  If this pointer is non-NULL, it indicates 
that an extra comma preceding the I/O list was encountered.  This signals a 
possible alternate form of the I/O statement.

If the alternate form was used, the io_unit expression will come in as a 
character type of expression.  If so, it is assumed to be a format expression 
and not a unit, and the pointers involved are adjusted so that the format 
expression refers to the character expression in io_unit, and the io_unit is 
pointed to the default unit for the io_kind.

The io_kind is passed in extra_comma->value.logical.  I used this since it is an 
int and can hold the enumerator type without problem.  Another option would be 
to add "io_kind k" to the union for value in gfc_expr, giving more readable code.

Regression tested on x86-64.

OK for trunk?

Jerry

2008-04-27  Jerry DeLisle  <jvdelisle@gcc.gnu.org>

	PR fortran/33268
	* gfortran.h: Add extra_comma pointer to gfc_dt structure.
	* io.c (gfc_free_dt): Free extra_comma.
	(gfc_resolve_dt): If an extra comma was encountered and io_unit is type
	BT_CHARACTER, resolve to format_expr and set default unit.  Error if
	io_kind is M_WRITE. (match_io):  Match the extra comma and set new
	pointer, extra_comma.


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