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From: Szabolcs Nagy <nsz@port70.net>
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Subject: Re: Bug report: strtod drops LSB
Date: Wed, 25 Sep 2019 17:06:32 +0200
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* Anastasios <antonbachin@yahoo.com> [2019-09-25 09:32:35 -0500]:
> Hello,
>=20
> Consider this program, strtod.c:
>=20
> =C2=A0 =C2=A0=C2=A0#include <stdlib.h>
> =C2=A0 =C2=A0=C2=A0#include <stdio.h>
>=20
> =C2=A0 =C2=A0=C2=A0int main()
> =C2=A0 =C2=A0=C2=A0{
> =C2=A0 =C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0printf("%lf\n", strtod("28368695230=
6183", NULL));
> =C2=A0 =C2=A0=C2=A0}
>=20
> With current musl master from Git:
>=20
> =C2=A0 =C2=A0=C2=A0$ musl-gcc -static strtod.c -o a.musl
> =C2=A0 =C2=A0 $ ./a.musl
> =C2=A0 =C2=A0 283686952306176.000000
>=20
> By comparison, with glibc:
>=20
> =C2=A0 =C2=A0 $ gcc -static strtod.c -o a.glibc
> =C2=A0 =C2=A0 $ ./a.glibc
> =C2=A0 =C2=A0 283686952306183.000000
>=20

works for me on both i486-linux-musl and aarch64-linux-musl.
i have no idea what can cause such bug.

can you try printf with %a and strtod(...)=3D=3D0x1.020304050607p+48
to see if it's printf %lf that goes wrong?

> The correct binary representation of this float is
>=20
> =C2=A0 =C2=A0 0x42f0203040506070
>=20
> but musl strtod produces
>=20
> =C2=A0 =C2=A0 0x42f0203040506000
>=20
> i.e., it fails to set the LSB. I examined this while ruling out printf as=
 the cause.