fortran/89100: Default widths with -fdec-format-defaults

gcc/fortran ChangeLog:

2019-05-22  Jeff Law  <law@redhat.com>
            Mark Eggleston  <mark.eggleston@codethink.com>

        PR fortran/89100
        * gfortran.texi: Add Default widths for F, G and I format
        descriptors to Extensions section.
        * invoke.texi: Add -fdec-format-defaults
        * io.c (check_format): Use default widths for i, f and g when
        flag_dec_format_defaults is enabled.
        * lang.opt: Add new option.
        * options.c (set_dec_flags): Add SET_BITFLAG for
        flag_dec_format_defaults.


gcc/testsuite ChangeLog:

2019-05-22  Mark Eggleston  <mark.eggleston@codethink.com>

        PR fortran/89100
        * gfortran.dg/fmt_f_default_field_width_1.f90: New test.
        * gfortran.dg/fmt_f_default_field_width_2.f90: New test.
        * gfortran.dg/fmt_f_default_field_width_3.f90: New test.
        * gfortran.dg/fmt_g_default_field_width_1.f90: New test.
        * gfortran.dg/fmt_g_default_field_width_2.f90: New test.
        * gfortran.dg/fmt_g_default_field_width_3.f90: New test.
        * gfortran.dg/fmt_i_default_field_width_1.f90: New test.
        * gfortran.dg/fmt_i_default_field_width_2.f90: New test.
        * gfortran.dg/fmt_i_default_field_width_3.f90: New test.


libgfortran ChangeLog:

2019-05-22  Jeff Law  <law@redhat.com>

        PR fortran/89100
        * io/format.c (parse_format_list): set default width when the
        IOPARM_DT_DEC_EXT flag is set for i, f and g.
        * io/io.h: add default_width_for_integer, default_width_for_float
        and default_precision_for_float.
        * io/write.c (write_boz): extra parameter giving length of data
        corresponding to the type's kind.
        (write_b): pass data length as extra parameter in calls to
        write_boz.
        (write_o): pass data length as extra parameter in calls to
        write_boz.
        (write_z): pass data length as extra parameter in calls to
        write_boz.
        (size_from_kind): also set size is default width is set.
        * io/write_float.def (build_float_string): new paramter inserted
        before result parameter. If default width use values passed
        instead of the values in fnode.
        (FORMAT_FLOAT): macro modified to check for default width and
        calls to build_float_string to pass in default width.
        (get_float_string): set width and precision to defaults when
        needed.

From-SVN: r271511

6 files changed, 77 insertions, 14 deletions

diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index e6ae6bc..f119e74 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,3 +1,16 @@
+2019-05-22  Jeff Law  <law@redhat.com>
+	    Mark Eggleston  <mark.eggleston@codethink.com>
+
+	PR fortran/89100
+	* gfortran.texi: Add Default widths for F, G and I format
+	descriptors to Extensions section.
+	* invoke.texi: Add -fdec-format-defaults
+	* io.c (check_format): Use default widths for i, f and g when
+	flag_dec_format_defaults is enabled.
+	* lang.opt: Add new option.
+	* options.c (set_dec_flags): Add SET_BITFLAG for
+	flag_dec_format_defaults.
+
 2019-05-21  Janne Blomqvist  <jb@gcc.gnu.org>
 
 	PR libfortran/90038
diff --git a/gcc/fortran/gfortran.texi b/gcc/fortran/gfortran.texi
index 6c746e3..57461e0 100644
--- a/gcc/fortran/gfortran.texi
+++ b/gcc/fortran/gfortran.texi
@@ -1576,6 +1576,7 @@ additional compatibility extensions along with those enabled by
 * X format descriptor without count field::
 * Commas in FORMAT specifications::
 * Missing period in FORMAT specifications::
+* Default widths for F@comma{} G and I format descriptors::
 * I/O item lists::
 * @code{Q} exponent-letter::
 * BOZ literal constants::
@@ -1782,6 +1783,22 @@ discouraged.
 10     FORMAT ('F4')
 @end smallexample
 
+@node Default widths for F@comma{} G and I format descriptors
+@subsection Default widths for @code{F}, @code{G} and @code{I} format descriptors
+
+To support legacy codes, GNU Fortran allows width to be omitted from format
+specifications if and only if @option{-fdec-format-defaults} is given on the
+command line.  Default widths will be used. This is considered non-conforming
+code and is discouraged.
+
+@smallexample
+       REAL :: value1
+       INTEGER :: value2
+       WRITE(*,10) value1, value1, value2
+10     FORMAT ('F, G, I')
+@end smallexample
+
+
 @node I/O item lists
 @subsection I/O item lists
 @cindex I/O item lists
diff --git a/gcc/fortran/invoke.texi b/gcc/fortran/invoke.texi
index ec3b040..73b836e 100644
--- a/gcc/fortran/invoke.texi
+++ b/gcc/fortran/invoke.texi
@@ -117,16 +117,16 @@ by type.  Explanations are in the following sections.
 @item Fortran Language Options
 @xref{Fortran Dialect Options,,Options controlling Fortran dialect}.
 @gccoptlist{-fall-intrinsics -fbackslash -fcray-pointer -fd-lines-as-code @gol
--fd-lines-as-comments @gol
--fdec -fdec-structure -fdec-intrinsic-ints -fdec-static -fdec-math @gol
--fdec-include -fdefault-double-8 -fdefault-integer-8 -fdefault-real-8 @gol
--fdefault-real-10 -fdefault-real-16 -fdollar-ok -ffixed-line-length-@var{n} @gol
--ffixed-line-length-none -fpad-source -ffree-form -ffree-line-length-@var{n} @gol
--ffree-line-length-none -fimplicit-none -finteger-4-integer-8 @gol
--fmax-identifier-length -fmodule-private -ffixed-form -fno-range-check @gol
--fopenacc -fopenmp -freal-4-real-10 -freal-4-real-16 -freal-4-real-8 @gol
--freal-8-real-10 -freal-8-real-16 -freal-8-real-4 -std=@var{std}
--ftest-forall-temp
+-fd-lines-as-comments -fdec -fdec-structure -fdec-intrinsic-ints @gol
+-fdec-static -fdec-math -fdec-include -fdec-format-defaults @gol
+-fdefault-double-8 -fdefault-integer-8 -fdefault-real-8 -fdefault-real-10 @gol
+-fdefault-real-16 -fdollar-ok -ffixed-line-length-@var{n} @gol
+-ffixed-line-length-none -fpad-source -ffree-form @gol
+-ffree-line-length-@var{n} -ffree-line-length-none @gol
+-fimplicit-none -finteger-4-integer-8 -fmax-identifier-length @gol
+-fmodule-private -ffixed-form -fno-range-check -fopenacc -fopenmp @gol
+-freal-4-real-10 -freal-4-real-16 -freal-4-real-8 -freal-8-real-10 @gol
+-freal-8-real-16 -freal-8-real-4 -std=@var{std} -ftest-forall-temp
 }
 
 @item Preprocessing Options
@@ -283,6 +283,11 @@ Enable parsing of INCLUDE as a statement in addition to parsing it as
 INCLUDE line.  When parsed as INCLUDE statement, INCLUDE does not have to
 be on a single line and can use line continuations.
 
+@item -fdec-format-defaults
+@opindex @code{fdec-format-defaults}
+Enable format specifiers F, G and I to be used without width specifiers,
+default widths will be used instead.
+
 @item -fdollar-ok
 @opindex @code{fdollar-ok}
 @cindex @code{$}
diff --git a/gcc/fortran/io.c b/gcc/fortran/io.c
index 9828897..5711757 100644
--- a/gcc/fortran/io.c
+++ b/gcc/fortran/io.c
@@ -903,6 +903,13 @@ data_desc:
 
       if (u != FMT_POSINT)
 	{
+	  if (flag_dec_format_defaults)
+	    {
+	      /* Assume a default width based on the variable size.  */
+	      saved_token = u;
+	      break;
+	    }
+
 	  format_locus.nextc += format_string_pos;
 	  gfc_error ("Positive width required in format "
 			 "specifier %s at %L", token_to_string (t),
@@ -1027,6 +1034,13 @@ data_desc:
 	goto fail;
       if (t != FMT_ZERO && t != FMT_POSINT)
 	{
+	  if (flag_dec_format_defaults)
+	    {
+	      /* Assume the default width is expected here and continue lexing.  */
+	      value = 0; /* It doesn't matter what we set the value to here.  */
+	      saved_token = t;
+	      break;
+	    }
 	  error = nonneg_required;
 	  goto syntax;
 	}
@@ -1096,8 +1110,17 @@ data_desc:
 	goto fail;
       if (t != FMT_ZERO && t != FMT_POSINT)
 	{
-	  error = nonneg_required;
-	  goto syntax;
+	  if (flag_dec_format_defaults)
+	    {
+	      /* Assume the default width is expected here and continue lexing.  */
+	      value = 0; /* It doesn't matter what we set the value to here.  */
+	      saved_token = t;
+	    }
+	  else
+	    {
+	      error = nonneg_required;
+	      goto syntax;
+	    }
 	}
       else if (is_input && t == FMT_ZERO)
 	{
@@ -4368,8 +4391,8 @@ get_io_list:
     }
 
   /* See if we want to use defaults for missing exponents in real transfers
-     and other DEC runtime extensions.  */
-  if (flag_dec)
+     and other DEC runtime extensions. */
+  if (flag_dec_format_defaults)
     dt->dec_ext = 1;
 
   /* A full IO statement has been matched.  Check the constraints.  spec_end is
diff --git a/gcc/fortran/lang.opt b/gcc/fortran/lang.opt
index 80edc11..4d2340a 100644
--- a/gcc/fortran/lang.opt
+++ b/gcc/fortran/lang.opt
@@ -452,6 +452,10 @@ fdec-include
 Fortran Var(flag_dec_include)
 Enable legacy parsing of INCLUDE as statement.
 
+fdec-format-defaults
+Fortran Var(flag_dec_format_defaults)
+Enable default widths for i, f and g format specifiers.
+
 fdec-intrinsic-ints
 Fortran Var(flag_dec_intrinsic_ints)
 Enable kind-specific variants of integer intrinsic functions.
diff --git a/gcc/fortran/options.c b/gcc/fortran/options.c
index 02970d5..4f91486 100644
--- a/gcc/fortran/options.c
+++ b/gcc/fortran/options.c
@@ -74,6 +74,7 @@ set_dec_flags (int value)
   SET_BITFLAG (flag_dec_static, value, value);
   SET_BITFLAG (flag_dec_math, value, value);
   SET_BITFLAG (flag_dec_include, value, value);
+  SET_BITFLAG (flag_dec_format_defaults, value, value);
 }
 
 /* Finalize DEC flags.  */