The dimension system in GNAT now allows to compare a dimensioned
expression with a literal, but it issues a warning in this case if the
literal is not zero.
The following code compiles with warnings:
$ gcc -c use_dims.adb
1. with System.Dim.Mks; use System.Dim.Mks;
2.
3. procedure Use_Dims with SPARK_Mode is
4. X : Speed := 0.0;
5. Y : Speed := 1.0;
|
>>> warning: assumed to be "1.0 m.s**(-1)"
6. begin
7. if X = 0.0 then
8. null;
9. elsif 0.0 = X then
10. null;
11. elsif X = 1.0 then
|
>>> warning: assumed to be "1.0 m.s**(-1)"
12. null;
13. end if;
14. end Use_Dims;
Tested on x86_64-pc-linux-gnu, committed on trunk
2017-10-20 Yannick Moy <m...@adacore.com>
* sem_dim.adb (Analyze_Dimension_Binary_Op): Accept with a warning to
compare a dimensioned expression with a literal.
(Dim_Warning_For_Numeric_Literal): Do not issue a warning for the
special value zero.
* doc/gnat_ugn/gnat_and_program_execution.rst: Update description of
dimensionality system in GNAT.
* gnat_ugn.texi: Regenerate.
Index: doc/gnat_ugn/gnat_and_program_execution.rst
===================================================================
--- doc/gnat_ugn/gnat_and_program_execution.rst (revision 253938)
+++ doc/gnat_ugn/gnat_and_program_execution.rst (working copy)
@@ -3611,21 +3611,27 @@
``Acceleration``.
The dimensionality checks for relationals use the same rules as
-for "+" and "-"; thus
+for "+" and "-", except when comparing to a literal; thus
.. code-block:: ada
- acc > 10.0
+ acc > len
is equivalent to
.. code-block:: ada
- acc-10.0 > 0.0
+ acc-len > 0.0
-and is thus illegal. Analogously a conditional expression
-requires the same dimension vector for each branch.
+and is thus illegal, but
+ .. code-block:: ada
+
+ acc > 10.0
+
+is accepted with a warning. Analogously a conditional expression requires the
+same dimension vector for each branch (with no exception for literals).
+
The dimension vector of a type conversion :samp:`T({expr})` is defined
as follows, based on the nature of ``T``:
Index: sem_dim.adb
===================================================================
--- sem_dim.adb (revision 253941)
+++ sem_dim.adb (working copy)
@@ -1577,6 +1577,20 @@
then
null;
+ -- Numeric literal case. Issue a warning to indicate the
+ -- literal is treated as if its dimension matches the type
+ -- dimension.
+
+ elsif Nkind_In (Original_Node (L), N_Real_Literal,
+ N_Integer_Literal)
+ then
+ Dim_Warning_For_Numeric_Literal (L, Etype (R));
+
+ elsif Nkind_In (Original_Node (R), N_Real_Literal,
+ N_Integer_Literal)
+ then
+ Dim_Warning_For_Numeric_Literal (R, Etype (L));
+
else
Error_Dim_Msg_For_Binary_Op (N, L, R);
end if;
@@ -2724,6 +2738,24 @@
procedure Dim_Warning_For_Numeric_Literal (N : Node_Id; Typ : Entity_Id) is
begin
+ -- Consider the literal zero (integer 0 or real 0.0) to be of any
+ -- dimension.
+
+ case Nkind (Original_Node (N)) is
+ when N_Real_Literal =>
+ if Expr_Value_R (N) = Ureal_0 then
+ return;
+ end if;
+
+ when N_Integer_Literal =>
+ if Expr_Value (N) = Uint_0 then
+ return;
+ end if;
+
+ when others =>
+ null;
+ end case;
+
-- Initialize name buffer
Name_Len := 0;
Index: gnat_ugn.texi
===================================================================
--- gnat_ugn.texi (revision 253938)
+++ gnat_ugn.texi (working copy)
@@ -21,7 +21,7 @@
@copying
@quotation
-GNAT User's Guide for Native Platforms , Oct 14, 2017
+GNAT User's Guide for Native Platforms , Oct 20, 2017
AdaCore
@@ -12474,8 +12474,8 @@
This switch activates warnings for exception usage when pragma Restrictions
(No_Exception_Propagation) is in effect. Warnings are given for implicit or
explicit exception raises which are not covered by a local handler, and for
-exception handlers which do not cover a local raise. The default is that these
-warnings are not given.
+exception handlers which do not cover a local raise. The default is that
+these warnings are given for units that contain exception handlers.
@item @code{-gnatw.X}
@@ -22901,12 +22901,12 @@
@code{Acceleration}.
The dimensionality checks for relationals use the same rules as
-for "+" and "-"; thus
+for "+" and "-", except when comparing to a literal; thus
@quotation
@example
-acc > 10.0
+acc > len
@end example
@end quotation
@@ -22915,13 +22915,22 @@
@quotation
@example
-acc-10.0 > 0.0
+acc-len > 0.0
@end example
@end quotation
-and is thus illegal. Analogously a conditional expression
-requires the same dimension vector for each branch.
+and is thus illegal, but
+@quotation
+
+@example
+acc > 10.0
+@end example
+@end quotation
+
+is accepted with a warning. Analogously a conditional expression requires the
+same dimension vector for each branch (with no exception for literals).
+
The dimension vector of a type conversion @code{T(@emph{expr})} is defined
as follows, based on the nature of @code{T}:
