Re: Wrong unconditional dependency on nanl

[Christophe Lyon <christophe dot lyon at linaro dot org>]

On Wed, 10 Oct 2018 at 11:41, Corinna Vinschen <vinschen@redhat.com> wrote:
>
> On Oct  8 15:06, Christophe Lyon wrote:
> > Hello,
> >
> > On aarch64 I've notice that a simple hello.c fails to link against
> > current newlib master:
> > .../aarch64-elf/libc/usr/lib/libc.a(lib_a-strtorx.o): In function `ULtox':
> > .../newlib/libc/stdlib/strtorx.c:92: undefined reference to `nanl'
> >
> > It seems to me that an unconditional dependency on nanl() was
> > introduced by commit
> > 6c212a8b7873703c4f98c6b68579b234918be83a
> > Author: Masamichi Hosoda <trueroad@trueroad.jp>
> > Date:   Thu Aug 16 09:18:50 2018 +0900
> >     Fix strtod ("nan") and strtold ("nan") returns wrong negative NaN
> >
> > but I'm not sure how to fix this as I did not follow the discussion
> > around this patch.
> >
> > It seems to me that nanl() is only defined if _LDBL_EQ_DBL
> > (newlib/libm/common/nanl.c), but the patch above introduces a call to
> > nanl() in a code path where !defined (_LDBL_EQ_DBL)
> >
> > This I suspect the problem is present on other targets, too ?
>
> Cygwin has it's own nanl implemented in winsup/cygwin/math/nanl.c.
>
> However, dropping it there and using a patch like this:
>
> diff --git a/newlib/libm/common/nanl.c b/newlib/libm/common/nanl.c
> index 40f898109edd..b8ae63ea7539 100644
> --- a/newlib/libm/common/nanl.c
> +++ b/newlib/libm/common/nanl.c
> @@ -38,5 +38,11 @@ nanl (const char *tagp)
>  {
>    return nan(tagp);
>  }
> +#elif __GNUC_PREREQ (3, 3)
> +long double
> +nanl (const char *tagp)
> +{
> +  return __builtin_nanl("");
> +}
>  #endif
>
> should help along all targets, right?  Is there any target still using
> a pre-3.3 GCC?
>

It does help on aarch64-elf, but a change to rdimon.specs is required
because libc now depends on libm: this can be seen when compiling a
C++ hello.cpp.

In addition, there's still a warning:
newlib/libc/stdlib/strtorx.c:92:24: warning: implicit declaration of
function ‘nanl’

Christophe


>
> Corinna
>
> --
> Corinna Vinschen
> Cygwin Maintainer
> Red Hat