https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125255
Bug ID: 125255
Summary: Inaccurate printing of floating point values even when
numbers are exactly representable
Product: gcc
Version: 16.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: algol68
Assignee: algol68 at gcc dot gnu.org
Reporter: jpl.algol68 at gmail dot com
Target Milestone: ---
Created attachment 64420
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=64420&action=edit
Additional information received from N.H.F. Beebe
Two issues regarding IEEE754 with respect to inf and nan.
The first example below shows that divide by zero does not produce the expected
IEEE754 of inf.
begin
real x, y, z;
x := 1.0;
y := 0.0;
z := x / y;
puts("If Algol 68 arithmetic follows IEEE 754, this should be Infinity: " +
float(z, 30, 20, 0) + "'n");
skip
end
Instead, this program enters and infinite loop.
The second example shows 0.0/0.0 does not produced expected IEEE754 nan:
begin
real x, y, z;
x := 0.0;
y := 0.0;
z := x / y;
puts("If Algol 68 arithmetic follows IEEE 754, this should be NaN: " +
float(z, 30, 20, 0) + "'n");
skip
end
Instead, this test file core dumps at run-time:
standard.a68:429: runtime error: bound -2147483647 out of range [1:16]
This dump is believed to happen in:
proc dig_char = (int x) char: "0123456789abcdef"[x+1];
The procedure dig_char is called by `subfixed' and others.
These examples were brought to our attention and contributed by Nelson H. F.
Beebe and are thankfully acknowledged.
Attachment contains additional related information received from N.H.F. Beebe.
