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[Ada] Vectors: spurious error in -gnatwE mode

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This patch fixes a bug in which if Ada.Containers.Vectors is instantiated with
an Index_Type such that Index_Type'Base'Last is less than Count_Type'Last, and
the -gnatwE switch is used, the compiler gives spurious error messages.

The following test should compile quietly with -gnatwE:

gnatmake short_vectors.ads -gnatwa -gnatwE -gnatf

with Ada.Containers.Vectors;
package Short_Vectors is

   type Index_Type is range 1 .. 256;

   package Map_Pkg is new Ada.Containers.Vectors
     (Index_Type => Index_Type,
      Element_Type => Integer);

end Short_Vectors;

2018-05-23  Bob Duff  <duff@adacore.com>

gcc/ada/

	* libgnat/a-convec.adb: (Insert, Insert_Space): Suppress warnings. The
	code in question is not reachable in the case where Count_Type'Last is
	out of range.

From-SVN: r260590
This commit is contained in:
Bob Duff 2018-05-23 10:23:19 +00:00 • committed by Pierre-Marie de Rodat
parent 5e1c231ec7
commit aeaa0347e9
2 changed files with 14 additions and 2 deletions
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6
gcc/ada/ChangeLog
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@ -1,3 +1,9 @@
2018-05-23 Bob Duff <duff@adacore.com>
* libgnat/a-convec.adb: (Insert, Insert_Space): Suppress warnings. The
code in question is not reachable in the case where Count_Type'Last is
out of range.
2018-05-23 Yannick Moy <moy@adacore.com>
* doc/gnat_rm/implementation_defined_pragmas.rst: Clarify meaning of

10
gcc/ada/libgnat/a-convec.adb
View file

@ -999,9 +999,12 @@ package body Ada.Containers.Vectors is
-- We know that No_Index (the same as Index_Type'First - 1) is
-- less than 0, so it is safe to compute the following sum without
-- fear of overflow.
-- fear of overflow. We need to suppress warnings, because
-- otherwise we get an error in -gnatwE mode.
pragma Warnings (Off);
Index := No_Index + Index_Type'Base (Count_Type'Last);
pragma Warnings (On);
if Index <= Index_Type'Last then
@ -1657,9 +1660,12 @@ package body Ada.Containers.Vectors is
-- We know that No_Index (the same as Index_Type'First - 1) is
-- less than 0, so it is safe to compute the following sum without
-- fear of overflow.
-- fear of overflow. We need to suppress warnings, because
-- otherwise we get an error in -gnatwE mode.
pragma Warnings (Off);
Index := No_Index + Index_Type'Base (Count_Type'Last);
pragma Warnings (On);
if Index <= Index_Type'Last then