https://gcc.gnu.org/g:3a0eabf75a7bad46807e34a7142abc15af3e20c8
commit r16-1879-g3a0eabf75a7bad46807e34a7142abc15af3e20c8
Author: Eric Botcazou <ebotca...@adacore.com>
Date: Wed May 21 15:15:48 2025 +0200
ada: Fix couple of issues in System.Value_D.Integer_To_Decimal function
The first issue is that the function would wrongly raise Constraint_Error
on the edge case where Val = 2**(Int'Size - 1) and Minus is not set.
The second issue is that the function takes a long time to deal with huge
negative exponents.
The change also contains minor consistency fixes for its counterpart that
is present in System.Value_F, namely Integer_To_Fixed.
gcc/ada/ChangeLog:
* libgnat/s-valued.adb (Integer_To_Decimal): Deal specifically with
Val = 2**(Int'Size - 1) if Minus is not set. Exit the loops when V
saturates to 0 in the case of (huge) negative exponents. Use Base
instead of B consistently in unsigned computations.
* libgnat/s-valuef.adb (Integer_To_Fixed): Use Base instead of B
consistently in unsigned computations.
Diff:
---
gcc/ada/libgnat/s-valued.adb | 42 +++++++++++++++++++++++++++---------------
gcc/ada/libgnat/s-valuef.adb | 12 ++++++------
2 files changed, 33 insertions(+), 21 deletions(-)
diff --git a/gcc/ada/libgnat/s-valued.adb b/gcc/ada/libgnat/s-valued.adb
index 57d5c04ab105..4f2e10204668 100644
--- a/gcc/ada/libgnat/s-valued.adb
+++ b/gcc/ada/libgnat/s-valued.adb
@@ -131,27 +131,39 @@ package body System.Value_D is
-- Local variables
- E : Uns := Uns (Extra2 / Base);
+ V : Uns := Val;
+ S : Integer := ScaleB;
+ E : Unsigned := Extra2 / Base;
begin
+ -- The implementation of Value_R uses fully symmetric arithmetics
+ -- but here we cannot handle 2**(Int'Size - 1) if Minus is not set.
+
+ if V = 2**(Int'Size - 1) and then not Minus then
+ E := Unsigned (V rem Uns (Base));
+ V := V / Uns (Base);
+ S := S + 1;
+ end if;
+
-- If the base of the value is 10 or its scaling factor is zero, then
-- add the scales (they are defined in the opposite sense) and apply
-- the result to the value, checking for overflow in the process.
- if Base = 10 or else ScaleB = 0 then
- declare
- S : Integer := ScaleB + Scale;
- V : Uns := Val;
-
+ if Base = 10 or else S = 0 then
begin
+ S := S + Scale;
+
while S < 0 loop
+ if V = 0 then
+ exit;
+ end if;
V := V / 10;
S := S + 1;
end loop;
while S > 0 loop
- if V <= (Uns'Last - E) / 10 then
- V := V * 10 + E;
+ if V <= (Uns'Last - Uns (E)) / 10 then
+ V := V * 10 + Uns (E);
S := S - 1;
E := 0;
else
@@ -167,10 +179,7 @@ package body System.Value_D is
else
declare
- B : constant Int := Int (Base);
- S : constant Integer := ScaleB;
-
- V : Uns := Val;
+ B : constant Int := Int (Base);
Y, Z, Q, R : Int;
@@ -186,7 +195,10 @@ package body System.Value_D is
Z := Safe_Expont (B, LS, 10 ** Integer'Max (0, -Scale));
for J in 1 .. LS loop
- V := V / Uns (B);
+ if V = 0 then
+ exit;
+ end if;
+ V := V / Uns (Base);
end loop;
end;
@@ -201,8 +213,8 @@ package body System.Value_D is
Z := 10 ** Integer'Max (0, -Scale);
for J in 1 .. LS loop
- if V <= (Uns'Last - E) / Uns (B) then
- V := V * Uns (B) + E;
+ if V <= (Uns'Last - Uns (E)) / Uns (Base) then
+ V := V * Uns (Base) + Uns (E);
E := 0;
else
Bad_Value (Str);
diff --git a/gcc/ada/libgnat/s-valuef.adb b/gcc/ada/libgnat/s-valuef.adb
index 03821aa4c1f5..6ea22117432d 100644
--- a/gcc/ada/libgnat/s-valuef.adb
+++ b/gcc/ada/libgnat/s-valuef.adb
@@ -236,8 +236,8 @@ package body System.Value_F is
-- but here we cannot handle 2**(Int'Size - 1) if Minus is not set.
if V = 2**(Int'Size - 1) and then not Minus then
- E := Unsigned (V rem Uns (B)) * Base + E / Base;
- V := V / Uns (B);
+ E := Unsigned (V rem Uns (Base)) * Base + E / Base;
+ V := V / Uns (Base);
S := S + 1;
end if;
@@ -261,8 +261,8 @@ package body System.Value_F is
E := 0;
exit;
end if;
- E := Unsigned (V rem Uns (B)) * Base + E / Base;
- V := V / Uns (B);
+ E := Unsigned (V rem Uns (Base)) * Base + E / Base;
+ V := V / Uns (Base);
end loop;
end;
@@ -277,8 +277,8 @@ package body System.Value_F is
Z := Num;
for J in 1 .. LS loop
- if V <= (Uns'Last - Uns (E / Base)) / Uns (B) then
- V := V * Uns (B) + Uns (E / Base);
+ if V <= (Uns'Last - Uns (E / Base)) / Uns (Base) then
+ V := V * Uns (Base) + Uns (E / Base);
E := (E rem Base) * Base;
else
Bad_Value (Str);
