Clean up some DFP interfaces

This cleans up a number of interfaces in dfp.c / dfp.h.  Specifically:

- The decimal_from_string / decimal_to_string routines are C++-ified
  to operate on std::string instead of character buffers.  In the
  decimal_from_string, the boolean return value now actually is bool
  instead of an int.

- The decimal_from_integral and decimal_from_doublest routines take
  an struct value as input.  This is not really appropriate at the low
  level the DFP routines sit, so this replaced them with new routines
  decimal_from_longest / decimal_from_ulongest / decimal_from_doublest
  that operate on contents instead.

- To mirror the decimal_from_[u]longest, a new decimal_to_longest
  routine is added as well, which can be used in unpack_long to
  avoid an unnecessary conversion via DOUBLEST.

Note that the decimal_from_longest / decimal_from_ulongest routines
are actually more powerful than decimal_from_integral: the old routine
would only accept integer *types* of at most four bytes size, while
the new routines accept all integer *values* that fit in an [u]int32_t,
no matter which type they came from.  The DFP tests are updated to
allow for this larger range of integers that can be converted.

gdb/ChangeLog:
2017-10-05  Ulrich Weigand  <uweigand@de.ibm.com>

	* dfp.h (MAX_DECIMAL_STRING): Move to dfp.c.
	(decimal_to_string): Return std::string object.
	(decimal_from_string): Accept std::string object.  Return bool.
	(decimal_from_integral, decimal_from_doublest): Remove.
	(decimal_from_longest): Add prototype.
	(decimal_from_ulongest): Likewise.
	(decimal_to_longest): Likewise.
	(decimal_from_doublest): Likewise.
	* dfp.c: Do not include "gdbtypes.h" or "value.h".
	(MAX_DECIMAL_STRING): Move here.
	(decimal_to_string): Return std::string object.
	(decimal_from_string): Accept std::string object.  Return bool.
	(decimal_from_integral): Remove, replace by ...
	(decimal_from_longest, decimal_from_ulongest): ... these new functions.
	(decimal_to_longest): New function.
	(decimal_from_floating): Remove, replace by ...
	(decimal_from_doublest): ... this new function.
	(decimal_to_doublest): Update to new decimal_to_string interface.

	* value.c (unpack_long): Use decimal_to_longest.
	* valops.c (value_cast): Use decimal_from_doublest instead of
	decimal_from_floating.  Use decimal_from_[u]longest isntead of
	decimal_from_integral.
	* valarith.c (value_args_as_decimal): Likewise.
	* valprint.c (print_decimal_floating): Update to new
	decimal_to_string interface.
	* printcmd.c (printf_decfloat): Likewise.
	* c-exp.y (parse_number): Update to new decimal_from_string interface.

gdb/testsuite/ChangeLog:
2017-10-05  Ulrich Weigand  <uweigand@de.ibm.com>

	* gdb.base/dfp-exprs.exp: Update tests to larger range of supported
	integer-to-dfp conversion.
	* gdb.base/dfp-test.exp: Likewise.

1 files changed, 8 insertions, 3 deletions

diff --git a/gdb/valops.c b/gdb/valops.c
index defc7d5..de4544c 100644
--- a/gdb/valops.c
+++ b/gdb/valops.c
@@ -471,13 +471,18 @@ value_cast (struct type *type, struct value *arg2)
       gdb_byte dec[16];
 
       if (code2 == TYPE_CODE_FLT)
-	decimal_from_floating (arg2, dec, dec_len, byte_order);
+	decimal_from_doublest (value_as_double (arg2),
+			       dec, dec_len, byte_order);
       else if (code2 == TYPE_CODE_DECFLOAT)
 	decimal_convert (value_contents (arg2), TYPE_LENGTH (type2),
 			 byte_order, dec, dec_len, byte_order);
+      /* The only option left is an integral type.  */
+      else if (TYPE_UNSIGNED (type2))
+	decimal_from_ulongest (value_as_long (arg2),
+			       dec, dec_len, byte_order);
       else
-	/* The only option left is an integral type.  */
-	decimal_from_integral (arg2, dec, dec_len, byte_order);
+	decimal_from_longest (value_as_long (arg2),
+			      dec, dec_len, byte_order);
 
       return value_from_decfloat (to_type, dec);
     }