Default missing exponents to 0 with -fdec.

	gcc/fortran/
	* gfortran.texi: Document.
	* gfortran.h (gfc_dt): New field default_exp.
	* primary.c (match_real_constant): Default exponent with -fdec.
	* io.c (match_io): Set dt.default_exp with -fdec.
	* ioparm.def (IOPARM_dt_default_exp): New.
	* trans-io.c (build_dt): Set IOPARM_dt_default_exp with -fdec.

	libgfortran/io/
	* io.h (IOPARM_DT_DEFAULT_EXP): New flag bit.
	* list_read.c (parse_real, read_real): Allow omission of exponent with
	IOPARM_DT_DEFAULT_EXP.
	* read.c (read_f): Ditto.

	gcc/testsuite/gfortran.dg/
	* dec_exp_1.f90, dec_exp_2.f90, dec_exp_3.f90: New testcases.

From-SVN: r241828

11 files changed, 110 insertions, 5 deletions

diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index baec7bf..b3cc871 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,3 +1,12 @@
+2016-11-03  Fritz Reese <fritzoreese@gmail.com>
+
+	* gfortran.texi: Document.
+	* gfortran.h (gfc_dt): New field default_exp.
+	* primary.c (match_real_constant): Default exponent with -fdec.
+	* io.c (match_io): Set dt.default_exp with -fdec.
+	* ioparm.def (IOPARM_dt_default_exp): New.
+	* trans-io.c (build_dt): Set IOPARM_dt_default_exp with -fdec.
+
 2016-11-03  Fritz O. Reese <fritzoreese@gmail.com>
 
 	* decl.c (gfc_match_parameter): Allow omitted '()' with -std=legacy.
diff --git a/gcc/fortran/gfortran.h b/gcc/fortran/gfortran.h
index b559e8a..3fb6f41 100644
--- a/gcc/fortran/gfortran.h
+++ b/gcc/fortran/gfortran.h
@@ -2336,6 +2336,7 @@ typedef struct
   gfc_expr *io_unit, *format_expr, *rec, *advance, *iostat, *size, *iomsg,
 	   *id, *pos, *asynchronous, *blank, *decimal, *delim, *pad, *round,
 	   *sign, *extra_comma, *dt_io_kind, *udtio;
+  char default_exp;
 
   gfc_symbol *namelist;
   /* A format_label of `format_asterisk' indicates the "*" format */
diff --git a/gcc/fortran/gfortran.texi b/gcc/fortran/gfortran.texi
index cd2c5a5..6de6c9b 100644
--- a/gcc/fortran/gfortran.texi
+++ b/gcc/fortran/gfortran.texi
@@ -1472,6 +1472,7 @@ compatibility extensions along with those enabled by @option{-std=legacy}.
 * Bitwise logical operators::
 * Extended I/O specifiers::
 * Legacy PARAMETER statements::
+* Default exponents::
 @end menu
 
 @node Old-style kind specifications
@@ -2713,6 +2714,14 @@ real c
 parameter c = 3.0e8
 @end smallexample
 
+@node Default exponents
+@subsection Default exponents
+@cindex exponent
+
+For compatibility, GNU Fortran supports a default exponent of zero in real
+constants with @option{-fdec}.  For example, @code{9e} would be
+interpreted as @code{9e0}, rather than an error.
+
 
 @node Extensions not implemented in GNU Fortran
 @section Extensions not implemented in GNU Fortran
diff --git a/gcc/fortran/io.c b/gcc/fortran/io.c
index 80cf830..04cc1a2 100644
--- a/gcc/fortran/io.c
+++ b/gcc/fortran/io.c
@@ -4167,6 +4167,10 @@ get_io_list:
 	goto syntax;
     }
 
+  /* See if we want to use defaults for missing exponents in real transfers.  */
+  if (flag_dec)
+    dt->default_exp = 1;
+
   /* A full IO statement has been matched.  Check the constraints.  spec_end is
      supplied for cases where no locus is supplied.  */
   m = check_io_constraints (k, dt, io_code, &spec_end);
diff --git a/gcc/fortran/ioparm.def b/gcc/fortran/ioparm.def
index f1bf733..4669187 100644
--- a/gcc/fortran/ioparm.def
+++ b/gcc/fortran/ioparm.def
@@ -118,4 +118,5 @@ IOPARM (dt,      round,		1 << 23, char2)
 IOPARM (dt,      sign,		1 << 24, char1)
 #define IOPARM_dt_f2003		      (1 << 25)
 #define IOPARM_dt_dtio		      (1 << 26)
+#define IOPARM_dt_default_exp	      (1 << 27)
 IOPARM (dt,      u,		0,	 pad)
diff --git a/gcc/fortran/primary.c b/gcc/fortran/primary.c
index 2101644..f26740d 100644
--- a/gcc/fortran/primary.c
+++ b/gcc/fortran/primary.c
@@ -483,7 +483,7 @@ backup:
 static match
 match_real_constant (gfc_expr **result, int signflag)
 {
-  int kind, count, seen_dp, seen_digits, is_iso_c;
+  int kind, count, seen_dp, seen_digits, is_iso_c, default_exponent;
   locus old_loc, temp_loc;
   char *p, *buffer, c, exp_char;
   gfc_expr *e;
@@ -494,6 +494,7 @@ match_real_constant (gfc_expr **result, int signflag)
 
   e = NULL;
 
+  default_exponent = 0;
   count = 0;
   seen_dp = 0;
   seen_digits = 0;
@@ -575,8 +576,14 @@ match_real_constant (gfc_expr **result, int signflag)
 
   if (!ISDIGIT (c))
     {
-      gfc_error ("Missing exponent in real number at %C");
-      return MATCH_ERROR;
+      /* With -fdec, default exponent to 0 instead of complaining.  */
+      if (flag_dec)
+	default_exponent = 1;
+      else
+	{
+	  gfc_error ("Missing exponent in real number at %C");
+	  return MATCH_ERROR;
+	}
     }
 
   while (ISDIGIT (c))
@@ -597,8 +604,8 @@ done:
   gfc_current_locus = old_loc;
   gfc_gobble_whitespace ();
 
-  buffer = (char *) alloca (count + 1);
-  memset (buffer, '\0', count + 1);
+  buffer = (char *) alloca (count + default_exponent + 1);
+  memset (buffer, '\0', count + default_exponent + 1);
 
   p = buffer;
   c = gfc_next_ascii_char ();
@@ -621,6 +628,8 @@ done:
 
       c = gfc_next_ascii_char ();
     }
+  if (default_exponent)
+    *p++ = '0';
 
   kind = get_kind (&is_iso_c);
   if (kind == -1)
diff --git a/gcc/fortran/trans-io.c b/gcc/fortran/trans-io.c
index 285e551..253a5ac 100644
--- a/gcc/fortran/trans-io.c
+++ b/gcc/fortran/trans-io.c
@@ -1911,6 +1911,9 @@ build_dt (tree function, gfc_code * code)
       if (dt->udtio)
 	mask |= IOPARM_dt_dtio;
 
+      if (dt->default_exp)
+	mask |= IOPARM_dt_default_exp;
+
       if (dt->namelist)
 	{
 	  if (dt->format_expr || dt->format_label)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 3b39583..2a7d336 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2016-11-03  Fritz Reese <fritzoreese@gmail.com>
+
+	* gfortran.dg/dec_exp_1.f90: New test.
+	* gfortran.dg/dec_exp_2.f90: Likewise.
+	* gfortran.dg/dec_exp_3.f90: Likewise.
+
 2016-11-03  Fritz O. Reese <fritzoreese@gmail.com>
 
 	* gfortran.dg/dec_parameter_1.f: New test.
diff --git a/gcc/testsuite/gfortran.dg/dec_exp_1.f90 b/gcc/testsuite/gfortran.dg/dec_exp_1.f90
new file mode 100644
index 0000000..c8b395a
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/dec_exp_1.f90
@@ -0,0 +1,35 @@
+! { dg-do run }
+! { dg-options "-fdec" }
+!
+! Test support for providing a default exponent of zero when unspecified in
+! real constants with -fdec.
+!
+
+subroutine asserteq (rexp, ract, msg)
+  real, intent(in) :: rexp, ract
+  character(*), intent(in) :: msg
+  if (rexp .ne. ract) then
+    write (*, '(A,F12.6,F12.6)') msg, rexp, ract
+    call abort()
+  endif
+end subroutine
+
+implicit none
+
+real, parameter :: r1 = 8e0
+real, parameter :: r2 = 8e ! { equivalent to 8e0 }
+real, volatile :: r3, r4
+character(2) :: s
+r3 = 8e ! { equivalent to 8e0 }
+s = '8e'
+
+read (s, *) r4
+
+call asserteq (r1, r2, "[const]")
+call asserteq (r1, r3, "[vol. ]")
+call asserteq (r1, r4, "[read ]")
+
+r4 = 8e + 48e
+call asserteq (56e, r4, "[sum ]")
+
+end
diff --git a/gcc/testsuite/gfortran.dg/dec_exp_2.f90 b/gcc/testsuite/gfortran.dg/dec_exp_2.f90
new file mode 100644
index 0000000..9137aab
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/dec_exp_2.f90
@@ -0,0 +1,13 @@
+! { dg-do compile }
+! { dg-options "" }
+!
+! Make sure we still see an error for missing exponents without -fdec.
+!
+
+implicit none
+
+real, parameter :: r1 = 8e ! { dg-error "Missing exponent" }
+real, volatile :: r2
+r2 = 8e ! { dg-error "Missing exponent" }
+
+end
diff --git a/gcc/testsuite/gfortran.dg/dec_exp_3.f90 b/gcc/testsuite/gfortran.dg/dec_exp_3.f90
new file mode 100644
index 0000000..34835a7
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/dec_exp_3.f90
@@ -0,0 +1,15 @@
+! { dg-do run "xfail *-*-*" }
+! { dg-options "" }
+!
+! Make sure we still see an error for missing exponents without -fdec.
+!
+
+implicit none
+
+real :: r
+character(2) :: s
+s = '8e'
+
+read (s, *) r ! { XFAIL "Bad real number" }
+
+end