* [Ada] Reference in Unbounded_String is almost never null
@ 2021-11-09 9:45 Pierre-Marie de Rodat
0 siblings, 0 replies; 2+ messages in thread
From: Pierre-Marie de Rodat @ 2021-11-09 9:45 UTC (permalink / raw)
To: gcc-patches; +Cc: Piotr Trojanek
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The underlying reference in Unbounded_String is almost never null, so
recently it was changed to a non-excluding type (to avoid runtime checks
that are almost never needed).
The low-level routines that modify that reference had to be adapted, but
only the Deallocate routine was adapted. This patch adapts the
Realloc_For_Chunk routine as well.
Tested on x86_64-pc-linux-gnu, committed on trunk
gcc/ada/
* libgnat/a-strunb.adb (Deallocate): Rename Reference_Copy to
Old, to make the code similar to other routines in this package.
(Realloc_For_Chunk): Use a temporary, deallocate the previous
string using a null-allowing copy of the string reference.
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diff --git a/gcc/ada/libgnat/a-strunb.adb b/gcc/ada/libgnat/a-strunb.adb
--- a/gcc/ada/libgnat/a-strunb.adb
+++ b/gcc/ada/libgnat/a-strunb.adb
@@ -506,11 +506,11 @@ package body Ada.Strings.Unbounded is
if Object.Reference /= Null_String'Access then
declare
- Reference_Copy : String_Access := Object.Reference;
+ Old : String_Access := Object.Reference;
-- The original reference cannot be null, so we must create a
-- copy which will become null when deallocated.
begin
- Deallocate (Reference_Copy);
+ Deallocate (Old);
Object.Reference := Null_Unbounded_String.Reference;
end;
Object.Last := 0;
@@ -833,9 +833,13 @@ package body Ada.Strings.Unbounded is
Tmp : constant String_Access :=
new String (1 .. New_Rounded_Up_Size);
+ Old : String_Access := Source.Reference;
+ -- The original reference cannot be null, so we must create a copy
+ -- which will become null when deallocated.
+
begin
Tmp (1 .. Source.Last) := Source.Reference (1 .. Source.Last);
- Free (Source.Reference);
+ Free (Old);
Source.Reference := Tmp;
end;
end if;
^ permalink raw reply [flat|nested] 2+ messages in thread
* [Ada] Reference in Unbounded_String is almost never null
@ 2021-10-25 15:09 Pierre-Marie de Rodat
0 siblings, 0 replies; 2+ messages in thread
From: Pierre-Marie de Rodat @ 2021-10-25 15:09 UTC (permalink / raw)
To: gcc-patches; +Cc: Piotr Trojanek
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There are two variants of the Ada.Strings.Unbounded_String package, with
and without atomic reference counters. The underlying pointer is never
null in one variant (and had a null-excluding type) and almost never
null in the other variant (and now has a null-excluding type as well).
Cleanup related to sync of contracts for GNATprove between both variants
of the package.
Tested on x86_64-pc-linux-gnu, committed on trunk
gcc/ada/
* libgnat/a-strunb.ads (Unbounded_String): Reference is never
null.
* libgnat/a-strunb.adb (Finalize): Copy reference while it needs
to be deallocated.
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diff --git a/gcc/ada/libgnat/a-strunb.adb b/gcc/ada/libgnat/a-strunb.adb
--- a/gcc/ada/libgnat/a-strunb.adb
+++ b/gcc/ada/libgnat/a-strunb.adb
@@ -505,8 +505,14 @@ package body Ada.Strings.Unbounded is
-- Note: Don't try to free statically allocated null string
if Object.Reference /= Null_String'Access then
- Deallocate (Object.Reference);
- Object.Reference := Null_Unbounded_String.Reference;
+ declare
+ Reference_Copy : String_Access := Object.Reference;
+ -- The original reference cannot be null, so we must create a
+ -- copy which will become null when deallocated.
+ begin
+ Deallocate (Reference_Copy);
+ Object.Reference := Null_Unbounded_String.Reference;
+ end;
Object.Last := 0;
end if;
end Finalize;
diff --git a/gcc/ada/libgnat/a-strunb.ads b/gcc/ada/libgnat/a-strunb.ads
--- a/gcc/ada/libgnat/a-strunb.ads
+++ b/gcc/ada/libgnat/a-strunb.ads
@@ -746,8 +746,8 @@ private
renames To_Unbounded_String;
type Unbounded_String is new AF.Controlled with record
- Reference : String_Access := Null_String'Access;
- Last : Natural := 0;
+ Reference : not null String_Access := Null_String'Access;
+ Last : Natural := 0;
end record with Put_Image => Put_Image;
procedure Put_Image
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