Re: [PATCH][RFC] libstdc++ Provide <cerrno> and <errno.h> for freestanding

Tomasz Kaminski <[email protected]> Wed, 5 Aug 2026 08:43:14 +0200
Newsgroups gmane.comp.gcc.patches,gmane.comp.gcc.libstdc++.devel
Message-ID <CAKvuMXAK_O646QDzHZHUH+5SbEw96KcSRjxKpPQgxBhnxeVg5w@mail.gmail.com>
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On Tue, Aug 4, 2026 at 6:01=E2=80=AFPM Jonathan Wakely <[email protected]=
om>
wrote:

>
>
> On Tue, 4 Aug 2026, 12:10 Tomasz Kaminski, <[email protected]> wrote:
>
>>
>>
>> On Mon, Aug 3, 2026 at 6:58=E2=80=AFPM Jonathan Wakely <[email protected]=
om>
>> wrote:
>>
>>> The <cerrno> header is freestanding in C++26. Since we don't have to be
>>> compatible with a C library or a kernel for freestanding, we can just
>>> define the error number macros to arbitrary values.
>>>
>>> We need to provide a consistent set of definitions whether <cerrno> or
>>> <errno.h> is included, and whether a freestanding header is included by
>>> using -ffreestanding with a full hosted installation, or with a
>>> non-hosted (i.e. --disable-hosted-libstdcxx) installation. We do not
>>> want a situation where including <errno.h> uses a system libc header an=
d
>>> defines one set of values, but <cerrno> provides our own freestanding
>>> values.
>>>
>>> The approach taken here is to install our own copy of <errno.h> which
>>> does #include_next <errno.h> for hosted and which defines its own value=
s
>>> for freestanding. Our <cerrno> will then find our own <errno.h> and so
>>> <cerrno> and <errno.h> will be consistent, and the macro values will
>>> always be the same for the freestanding headers.
>>>
>>> libstdc++-v3/ChangeLog:
>>>
>>>         * include/Makefile.am (c_base_freestanding): Move cerrno to
>>>         here from ...
>>>         (c_base_headers): ... here.
>>>         (c_compatibility_headers): Add errno.h.
>>>         * include/Makefile.in: Regenerate.
>>>         * include/c_compatibility/errno.h: Replace include <cerrno> wit=
h
>>>         include_next <errno.h>.
>>>         [!_GLIBCXX_HOSTED] (E2BIG,EACCES,EADDRINUSE,EADDRNOTAVAIL)
>>>         (EAFNOSUPPORT,EAGAIN,EALREADY,EBADF,EBADMSG,EBUSY,ECANCELED)
>>>         (ECHILD,ECONNABORTED,ECONNREFUSED,ECONNRESET,EDEADLK)
>>>         (EDESTADDRREQ,EDOM,EEXIST,EFAULT,EFBIG,EHOSTUNREACH,EIDRM)
>>>         (EILSEQ,EINPROGRESS,EINTR,EINVAL,EIO,EISCONN,EISDIR,ELOOP)
>>>         (EMFILE,EMLINK,EMSGSIZE,ENAMETOOLONG,ENETDOWN,ENETRESET)
>>>         (ENETUNREACH,ENFILE,ENOBUFS,ENODEV,ENOENT,ENOEXEC,ENOLCK)
>>>         (ENOLINK,ENOMEM,ENOMSG,ENOPROTOOPT,ENOSPC,ENOSYS,ENOTCONN)
>>>         (ENOTDIR,ENOTEMPTY,ENOTRECOVERABLE,ENOTSOCK,ENOTSUP,ENOTTY)
>>>         (ENXIO,EOPNOTSUPP,EOVERFLOW,EOWNERDEAD,EPERM,EPIPE,EPROTO)
>>>         (EPROTONOSUPPORT,EPROTOTYPE,ERANGE,EROFS,ESPIPE,ESRCH)
>>>         (ETIMEDOUT,ETXTBSY,EWOULDBLOCK,EXDEV): Define.
>>> ---
>>>
>>> I don't really like this patch, but sending it for comment.
>>>
>>> Every time we add our own <name.h> C header it complicates things, and
>>> we have various bug reports (and patches) related to those files causin=
g
>>> problems during bootstrap of obscure canadian-cross configurations.
>>>
>>> So I'm a bit concerned that adding <errno.h> just for Freestanding woul=
d
>>> end up causing regressions that affect Hosted builds too.
>>>
>> We are already conditionally installing more headers for Hosted builds, =
so
>> could we conditionally install the new header only for environments that
>> are
>> not hosted? This should avoid any potential impact on existing platforms=
.
>>
>
> That won't work, not consistently anyway. For freestanding, you can eithe=
r
> build GCC with --disable-hosted-libstdcxx or you can build a hosted
> implementation but then use -ffreestanding.
>
> If we install different headers for the non-hosted build, you would not b=
e
> able to include errno.h with -ffreestanding, or you would get the libc on=
e
> which would have different error numbers.
>
> Maybe that's ok, and users would need to use a consistent "really
> freestanding" or "hosted but used as freestanding" installation. But I
> think it would be surprising.
>
That where my suggestion for using has_include_next where comming from. If
you build with
--disable-hosted-libstdcxx you will get system errno.h regardless if you
use -ffreestanding or not.
And if you enable --disable-hosted-libstdcxx then you get a errno.h file
installed, that will
use __has_include_next and also pull libc errno.h file on the same target.
So result
will be consistent.

And errno.h does not really have operating system dependencies, so I assume
it could
exist on some freenstanding enviroments, and provide some system specific
constants.

>
>
>>>
>>>  libstdc++-v3/include/Makefile.am             |  3 +-
>>>  libstdc++-v3/include/Makefile.in             |  3 +-
>>>  libstdc++-v3/include/c_compatibility/errno.h | 91 +++++++++++++++++++-
>>>  3 files changed, 94 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/libstdc++-v3/include/Makefile.am
>>> b/libstdc++-v3/include/Makefile.am
>>> index 3c30aa21d6b5..18bb9f224563 100644
>>> --- a/libstdc++-v3/include/Makefile.am
>>> +++ b/libstdc++-v3/include/Makefile.am
>>> @@ -902,6 +902,7 @@ endif
>>>  c_base_srcdir =3D $(C_INCLUDE_DIR)
>>>  c_base_builddir =3D .
>>>  c_base_freestanding =3D \
>>> +       ${c_base_srcdir}/cerrno \
>>>         ${c_base_srcdir}/cfloat \
>>>         ${c_base_srcdir}/climits \
>>>         ${c_base_srcdir}/cstdalign \
>>> @@ -919,7 +920,6 @@ c_base_headers =3D \
>>>         ${c_base_srcdir}/cassert \
>>>         ${c_base_srcdir}/ccomplex \
>>>         ${c_base_srcdir}/cctype \
>>> -       ${c_base_srcdir}/cerrno \
>>>         ${c_base_srcdir}/cfenv \
>>>         ${c_base_srcdir}/cinttypes \
>>>         ${c_base_srcdir}/ciso646 \
>>> @@ -947,6 +947,7 @@ endif
>>>  if GLIBCXX_C_HEADERS_C_GLOBAL
>>>  c_compatibility_headers =3D \
>>>         ${c_compatibility_srcdir}/complex.h \
>>> +       ${c_compatibility_srcdir}/errno.h \
>>>         ${c_compatibility_srcdir}/fenv.h \
>>>         ${c_compatibility_srcdir}/tgmath.h \
>>>         ${c_compatibility_srcdir}/math.h \
>>> diff --git a/libstdc++-v3/include/Makefile.in
>>> b/libstdc++-v3/include/Makefile.in
>>> index d081481293ff..feb6665ca401 100644
>>> --- a/libstdc++-v3/include/Makefile.in
>>> +++ b/libstdc++-v3/include/Makefile.in
>>> @@ -1250,6 +1250,7 @@ experimental_bits_headers =3D \
>>>  c_base_srcdir =3D $(C_INCLUDE_DIR)
>>>  c_base_builddir =3D .
>>>  c_base_freestanding =3D \
>>> +       ${c_base_srcdir}/cerrno \
>>>         ${c_base_srcdir}/cfloat \
>>>         ${c_base_srcdir}/climits \
>>>         ${c_base_srcdir}/cstdalign \
>>> @@ -1265,7 +1266,6 @@ c_base_freestanding =3D \
>>>  @GLIBCXX_HOSTED_TRUE@  ${c_base_srcdir}/cassert \
>>>  @GLIBCXX_HOSTED_TRUE@  ${c_base_srcdir}/ccomplex \
>>>  @GLIBCXX_HOSTED_TRUE@  ${c_base_srcdir}/cctype \
>>> -@GLIBCXX_HOSTED_TRUE@  ${c_base_srcdir}/cerrno \
>>>  @GLIBCXX_HOSTED_TRUE@  ${c_base_srcdir}/cfenv \
>>>  @GLIBCXX_HOSTED_TRUE@  ${c_base_srcdir}/cinttypes \
>>>  @GLIBCXX_HOSTED_TRUE@  ${c_base_srcdir}/ciso646 \
>>> @@ -1287,6 +1287,7 @@ c_compatibility_srcdir =3D
>>> ${glibcxx_srcdir}/include/c_compatibility
>>>  c_compatibility_builddir =3D .
>>>  @GLIBCXX_C_HEADERS_C_GLOBAL_TRUE@c_compatibility_headers =3D \
>>>  @GLIBCXX_C_HEADERS_C_GLOBAL_TRUE@
>>> ${c_compatibility_srcdir}/complex.h \
>>> +@GLIBCXX_C_HEADERS_C_GLOBAL_TRUE@
>>> ${c_compatibility_srcdir}/errno.h \
>>>  @GLIBCXX_C_HEADERS_C_GLOBAL_TRUE@
>>> ${c_compatibility_srcdir}/fenv.h \
>>>  @GLIBCXX_C_HEADERS_C_GLOBAL_TRUE@
>>> ${c_compatibility_srcdir}/tgmath.h \
>>>  @GLIBCXX_C_HEADERS_C_GLOBAL_TRUE@
>>> ${c_compatibility_srcdir}/math.h \
>>> diff --git a/libstdc++-v3/include/c_compatibility/errno.h
>>> b/libstdc++-v3/include/c_compatibility/errno.h
>>> index 07e3c17e9173..3eea20e081bb 100644
>>> --- a/libstdc++-v3/include/c_compatibility/errno.h
>>> +++ b/libstdc++-v3/include/c_compatibility/errno.h
>>> @@ -29,6 +29,95 @@
>>>  #ifndef _GLIBCXX_ERRNO_H
>>>  #define _GLIBCXX_ERRNO_H 1
>>>
>>> -#include <cerrno>
>>> +#include <bits/c++config.h>
>>> +
>>> +#if _GLIBCXX_HOSTED
>>>
>> Should whe use _has_include_next(<errno.h>)? So pull this header
>> if it is provided?
>>
>
> It's required for hosted implementations, and we know it's always present
> because everybody can already include it today.
>
>
> +#include_next <errno.h>
>>> +// Adhere to section 17.4.1.2 clause 5 of ISO 14882:1998
>>> +#ifndef errno
>>> +#define errno errno
>>> +#endif
>>> +
>>> +#else
>>> +__thread inline int __errno_v =3D 0;
>>> +
>>> +#define errno __errno_v
>>> +
>>> +#define E2BIG  10007
>>> +#define EACCES  10013
>>> +#define EADDRINUSE  10098
>>> +#define EADDRNOTAVAIL  10099
>>> +#define EAFNOSUPPORT  10097
>>> +#define EAGAIN  10011
>>> +#define EALREADY  10114
>>> +#define EBADF  10009
>>> +#define EBADMSG  10074
>>> +#define EBUSY  10016
>>> +#define ECANCELED  10125
>>> +#define ECHILD  10010
>>> +#define ECONNABORTED  10103
>>> +#define ECONNREFUSED  10111
>>> +#define ECONNRESET  10104
>>> +#define EDEADLK  10035
>>> +#define EDESTADDRREQ  10089
>>> +#define EDOM  10033
>>> +#define EEXIST  10017
>>> +#define EFAULT  10014
>>> +#define EFBIG  10027
>>> +#define EHOSTUNREACH  10113
>>> +#define EIDRM  10043
>>> +#define EILSEQ  10084
>>> +#define EINPROGRESS  10115
>>> +#define EINTR  10004
>>> +#define EINVAL  10022
>>> +#define EIO  10005
>>> +#define EISCONN  10106
>>> +#define EISDIR  10021
>>> +#define ELOOP  10040
>>> +#define EMFILE  10024
>>> +#define EMLINK  10031
>>> +#define EMSGSIZE  10090
>>> +#define ENAMETOOLONG  10036
>>> +#define ENETDOWN  10100
>>> +#define ENETRESET  10102
>>> +#define ENETUNREACH  10101
>>> +#define ENFILE  10023
>>> +#define ENOBUFS  10105
>>> +#define ENODEV  10019
>>> +#define ENOENT  10002
>>> +#define ENOEXEC  10008
>>> +#define ENOLCK  10037
>>> +#define ENOLINK  10067
>>> +#define ENOMEM  10012
>>> +#define ENOMSG  10042
>>> +#define ENOPROTOOPT  10092
>>> +#define ENOSPC  10028
>>> +#define ENOSYS  10038
>>> +#define ENOTCONN  10107
>>> +#define ENOTDIR  10020
>>> +#define ENOTEMPTY  10039
>>> +#define ENOTRECOVERABLE  10131
>>> +#define ENOTSOCK  10088
>>> +#define ENOTSUP  10095
>>> +#define ENOTTY  10025
>>> +#define ENXIO  10006
>>> +#define EOPNOTSUPP  10095
>>> +#define EOVERFLOW  10075
>>> +#define EOWNERDEAD  10130
>>> +#define EPERM  10001
>>> +#define EPIPE  10032
>>> +#define EPROTO  10071
>>> +#define EPROTONOSUPPORT  10093
>>> +#define EPROTOTYPE  10091
>>> +#define ERANGE  10034
>>> +#define EROFS  10030
>>> +#define ESPIPE  10029
>>> +#define ESRCH  10003
>>> +#define ETIMEDOUT  10110
>>> +#define ETXTBSY  10026
>>> +#define EWOULDBLOCK  10011
>>> +#define EXDEV  10018
>>> +
>>> +#endif // HOSTED
>>>
>>>  #endif
>>> --
>>> 2.55.0
>>>
>>>

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<div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote g=
mail_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">On Tue, Aug 4, =
2026 at 6:01=E2=80=AFPM Jonathan Wakely &lt;<a href=3D"mailto:jwakely.gcc@g=
mail.com">[email protected]</a>&gt; wrote:<br></div><blockquote class=
=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rg=
b(204,204,204);padding-left:1ex"><div dir=3D"auto"><div><br><br><div class=
=3D"gmail_quote"><div dir=3D"ltr" class=3D"gmail_attr">On Tue, 4 Aug 2026, =
12:10 Tomasz Kaminski, &lt;<a href=3D"mailto:[email protected]" target=3D=
"_blank">[email protected]</a>&gt; wrote:<br></div><blockquote class=3D"g=
mail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204=
,204,204);padding-left:1ex"><div dir=3D"ltr"><div dir=3D"ltr"><br></div><br=
><div class=3D"gmail_quote"><div dir=3D"ltr" class=3D"gmail_attr">On Mon, A=
ug 3, 2026 at 6:58=E2=80=AFPM Jonathan Wakely &lt;<a href=3D"mailto:jwakely=
@redhat.com" rel=3D"noreferrer" target=3D"_blank">[email protected]</a>&gt=
; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px=
 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">The &lt=
;cerrno&gt; header is freestanding in C++26. Since we don&#39;t have to be<=
br>
compatible with a C library or a kernel for freestanding, we can just<br>
define the error number macros to arbitrary values.<br>
<br>
We need to provide a consistent set of definitions whether &lt;cerrno&gt; o=
r<br>
&lt;errno.h&gt; is included, and whether a freestanding header is included =
by<br>
using -ffreestanding with a full hosted installation, or with a<br>
non-hosted (i.e. --disable-hosted-libstdcxx) installation. We do not<br>
want a situation where including &lt;errno.h&gt; uses a system libc header =
and<br>
defines one set of values, but &lt;cerrno&gt; provides our own freestanding=
<br>
values.<br>
<br>
The approach taken here is to install our own copy of &lt;errno.h&gt; which=
<br>
does #include_next &lt;errno.h&gt; for hosted and which defines its own val=
ues<br>
for freestanding. Our &lt;cerrno&gt; will then find our own &lt;errno.h&gt;=
 and so<br>
&lt;cerrno&gt; and &lt;errno.h&gt; will be consistent, and the macro values=
 will<br>
always be the same for the freestanding headers.<br>
<br>
libstdc++-v3/ChangeLog:<br>
<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 * include/Makefile.am (c_base_freestanding): Mo=
ve cerrno to<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 here from ...<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 (c_base_headers): ... here.<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 (c_compatibility_headers): Add errno.h.<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 * include/Makefile.in: Regenerate.<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 * include/c_compatibility/errno.h: Replace incl=
ude &lt;cerrno&gt; with<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 include_next &lt;errno.h&gt;.<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 [!_GLIBCXX_HOSTED] (E2BIG,EACCES,EADDRINUSE,EAD=
DRNOTAVAIL)<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 (EAFNOSUPPORT,EAGAIN,EALREADY,EBADF,EBADMSG,EBU=
SY,ECANCELED)<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 (ECHILD,ECONNABORTED,ECONNREFUSED,ECONNRESET,ED=
EADLK)<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 (EDESTADDRREQ,EDOM,EEXIST,EFAULT,EFBIG,EHOSTUNR=
EACH,EIDRM)<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 (EILSEQ,EINPROGRESS,EINTR,EINVAL,EIO,EISCONN,EI=
SDIR,ELOOP)<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 (EMFILE,EMLINK,EMSGSIZE,ENAMETOOLONG,ENETDOWN,E=
NETRESET)<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 (ENETUNREACH,ENFILE,ENOBUFS,ENODEV,ENOENT,ENOEX=
EC,ENOLCK)<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 (ENOLINK,ENOMEM,ENOMSG,ENOPROTOOPT,ENOSPC,ENOSY=
S,ENOTCONN)<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 (ENOTDIR,ENOTEMPTY,ENOTRECOVERABLE,ENOTSOCK,ENO=
TSUP,ENOTTY)<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 (ENXIO,EOPNOTSUPP,EOVERFLOW,EOWNERDEAD,EPERM,EP=
IPE,EPROTO)<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 (EPROTONOSUPPORT,EPROTOTYPE,ERANGE,EROFS,ESPIPE=
,ESRCH)<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 (ETIMEDOUT,ETXTBSY,EWOULDBLOCK,EXDEV): Define.<=
br>
---<br>
<br>
I don&#39;t really like this patch, but sending it for comment.<br>
<br>
Every time we add our own &lt;name.h&gt; C header it complicates things, an=
d<br>
we have various bug reports (and patches) related to those files causing<br=
>
problems during bootstrap of obscure canadian-cross configurations.<br>
<br>
So I&#39;m a bit concerned that adding &lt;errno.h&gt; just for Freestandin=
g would<br>
end up causing regressions that affect Hosted builds too.<br></blockquote><=
div>We are already conditionally installing more headers for Hosted builds,=
 so</div><div>could we conditionally install the new header only for enviro=
nments that are</div><div>not hosted? This should avoid any potential impac=
t on existing platforms.</div></div></div></blockquote></div></div><div dir=
=3D"auto"><br></div><div dir=3D"auto">That won&#39;t work, not consistently=
 anyway. For freestanding, you can either build GCC with --disable-hosted-l=
ibstdcxx or you can build a hosted implementation but then use -ffreestandi=
ng.</div><div dir=3D"auto"><br></div><div dir=3D"auto">If we install differ=
ent headers for the non-hosted build, you would not be able to include errn=
o.h with -ffreestanding, or you would get the libc one which would have dif=
ferent error numbers.</div><div dir=3D"auto"><br></div><div dir=3D"auto">Ma=
ybe that&#39;s ok, and users would need to use a consistent &quot;really fr=
eestanding&quot; or &quot;hosted but used as freestanding&quot; installatio=
n. But I think it would be surprising.=C2=A0</div></div></blockquote><div>T=
hat where my suggestion for using has_include_next where comming from. If y=
ou build with</div><div>--disable-hosted-libstdcxx you will get system errn=
o.h regardless if you use=C2=A0-ffreestanding or not.</div><div>And if you =
enable=C2=A0--disable-hosted-libstdcxx then you get a errno.h file installe=
d, that will</div><div>use __has_include_next and also pull libc errno.h fi=
le on the same target. So result</div><div>will be consistent.</div><div><b=
r></div><div>And errno.h does not really have operating system dependencies=
, so I assume it could</div><div>exist on some freenstanding enviroments, a=
nd provide some system specific constants.</div><blockquote class=3D"gmail_=
quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,=
204);padding-left:1ex"><div dir=3D"auto"><div dir=3D"auto"></div><div dir=
=3D"auto"><br></div><div dir=3D"auto"><div class=3D"gmail_quote"><blockquot=
e class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px s=
olid rgb(204,204,204);padding-left:1ex"><div dir=3D"ltr"><div class=3D"gmai=
l_quote"><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8e=
x;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
<br>
=C2=A0libstdc++-v3/include/Makefile.am=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0|=C2=A0 3 +-<br>
=C2=A0libstdc++-v3/include/Makefile.in=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0|=C2=A0 3 +-<br>
=C2=A0libstdc++-v3/include/c_compatibility/errno.h | 91 +++++++++++++++++++=
-<br>
=C2=A03 files changed, 94 insertions(+), 3 deletions(-)<br>
<br>
diff --git a/libstdc++-v3/include/Makefile.am b/libstdc++-v3/include/Makefi=
le.am<br>
index 3c30aa21d6b5..18bb9f224563 100644<br>
--- a/libstdc++-v3/include/Makefile.am<br>
+++ b/libstdc++-v3/include/Makefile.am<br>
@@ -902,6 +902,7 @@ endif<br>
=C2=A0c_base_srcdir =3D $(C_INCLUDE_DIR)<br>
=C2=A0c_base_builddir =3D .<br>
=C2=A0c_base_freestanding =3D \<br>
+=C2=A0 =C2=A0 =C2=A0 =C2=A0${c_base_srcdir}/cerrno \<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ${c_base_srcdir}/cfloat \<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ${c_base_srcdir}/climits \<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ${c_base_srcdir}/cstdalign \<br>
@@ -919,7 +920,6 @@ c_base_headers =3D \<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ${c_base_srcdir}/cassert \<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ${c_base_srcdir}/ccomplex \<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ${c_base_srcdir}/cctype \<br>
-=C2=A0 =C2=A0 =C2=A0 =C2=A0${c_base_srcdir}/cerrno \<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ${c_base_srcdir}/cfenv \<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ${c_base_srcdir}/cinttypes \<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ${c_base_srcdir}/ciso646 \<br>
@@ -947,6 +947,7 @@ endif<br>
=C2=A0if GLIBCXX_C_HEADERS_C_GLOBAL<br>
=C2=A0c_compatibility_headers =3D \<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ${c_compatibility_srcdir}/complex.h \<br>
+=C2=A0 =C2=A0 =C2=A0 =C2=A0${c_compatibility_srcdir}/errno.h \<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ${c_compatibility_srcdir}/fenv.h \<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ${c_compatibility_srcdir}/tgmath.h \<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ${c_compatibility_srcdir}/math.h \<br>
diff --git a/libstdc++-v3/include/Makefile.in b/libstdc++-v3/include/Makefi=
le.in<br>
index d081481293ff..feb6665ca401 100644<br>
--- a/libstdc++-v3/include/Makefile.in<br>
+++ b/libstdc++-v3/include/Makefile.in<br>
@@ -1250,6 +1250,7 @@ experimental_bits_headers =3D \<br>
=C2=A0c_base_srcdir =3D $(C_INCLUDE_DIR)<br>
=C2=A0c_base_builddir =3D .<br>
=C2=A0c_base_freestanding =3D \<br>
+=C2=A0 =C2=A0 =C2=A0 =C2=A0${c_base_srcdir}/cerrno \<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ${c_base_srcdir}/cfloat \<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ${c_base_srcdir}/climits \<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ${c_base_srcdir}/cstdalign \<br>
@@ -1265,7 +1266,6 @@ c_base_freestanding =3D \<br>
=C2=A0@GLIBCXX_HOSTED_TRUE@=C2=A0 ${c_base_srcdir}/cassert \<br>
=C2=A0@GLIBCXX_HOSTED_TRUE@=C2=A0 ${c_base_srcdir}/ccomplex \<br>
=C2=A0@GLIBCXX_HOSTED_TRUE@=C2=A0 ${c_base_srcdir}/cctype \<br>
-@GLIBCXX_HOSTED_TRUE@=C2=A0 ${c_base_srcdir}/cerrno \<br>
=C2=A0@GLIBCXX_HOSTED_TRUE@=C2=A0 ${c_base_srcdir}/cfenv \<br>
=C2=A0@GLIBCXX_HOSTED_TRUE@=C2=A0 ${c_base_srcdir}/cinttypes \<br>
=C2=A0@GLIBCXX_HOSTED_TRUE@=C2=A0 ${c_base_srcdir}/ciso646 \<br>
@@ -1287,6 +1287,7 @@ c_compatibility_srcdir =3D ${glibcxx_srcdir}/include/=
c_compatibility<br>
=C2=A0c_compatibility_builddir =3D .<br>
=C2=A0@GLIBCXX_C_HEADERS_C_GLOBAL_TRUE@c_compatibility_headers =3D \<br>
=C2=A0@GLIBCXX_C_HEADERS_C_GLOBAL_TRUE@=C2=A0 =C2=A0 =C2=A0 ${c_compatibili=
ty_srcdir}/complex.h \<br>
+@GLIBCXX_C_HEADERS_C_GLOBAL_TRUE@=C2=A0 =C2=A0 =C2=A0 ${c_compatibility_sr=
cdir}/errno.h \<br>
=C2=A0@GLIBCXX_C_HEADERS_C_GLOBAL_TRUE@=C2=A0 =C2=A0 =C2=A0 ${c_compatibili=
ty_srcdir}/fenv.h \<br>
=C2=A0@GLIBCXX_C_HEADERS_C_GLOBAL_TRUE@=C2=A0 =C2=A0 =C2=A0 ${c_compatibili=
ty_srcdir}/tgmath.h \<br>
=C2=A0@GLIBCXX_C_HEADERS_C_GLOBAL_TRUE@=C2=A0 =C2=A0 =C2=A0 ${c_compatibili=
ty_srcdir}/math.h \<br>
diff --git a/libstdc++-v3/include/c_compatibility/errno.h b/libstdc++-v3/in=
clude/c_compatibility/errno.h<br>
index 07e3c17e9173..3eea20e081bb 100644<br>
--- a/libstdc++-v3/include/c_compatibility/errno.h<br>
+++ b/libstdc++-v3/include/c_compatibility/errno.h<br>
@@ -29,6 +29,95 @@<br>
=C2=A0#ifndef _GLIBCXX_ERRNO_H<br>
=C2=A0#define _GLIBCXX_ERRNO_H 1<br>
<br>
-#include &lt;cerrno&gt;<br>
+#include &lt;bits/c++config.h&gt;<br>
+<br>
+#if _GLIBCXX_HOSTED<br></blockquote><div>Should whe use _has_include_next(=
&lt;errno.h&gt;)? So pull this header</div><div>if it is provided?=C2=A0</d=
iv></div></div></blockquote></div></div><div dir=3D"auto"><br></div><div di=
r=3D"auto">It&#39;s required for hosted implementations, and we know it&#39=
;s always present because everybody can already include it today.</div><div=
 dir=3D"auto"><br></div><div dir=3D"auto"><br></div><div dir=3D"auto"><div =
class=3D"gmail_quote"><blockquote class=3D"gmail_quote" style=3D"margin:0px=
 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><di=
v dir=3D"ltr"><div class=3D"gmail_quote"><blockquote class=3D"gmail_quote" =
style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);pa=
dding-left:1ex">
+#include_next &lt;errno.h&gt;<br>
+// Adhere to section 17.4.1.2 clause 5 of ISO 14882:1998<br>
+#ifndef errno<br>
+#define errno errno<br>
+#endif<br>
+<br>
+#else<br>
+__thread inline int __errno_v =3D 0;<br>
+<br>
+#define errno __errno_v<br>
+<br>
+#define E2BIG=C2=A0 10007<br>
+#define EACCES=C2=A0 10013<br>
+#define EADDRINUSE=C2=A0 10098<br>
+#define EADDRNOTAVAIL=C2=A0 10099<br>
+#define EAFNOSUPPORT=C2=A0 10097<br>
+#define EAGAIN=C2=A0 10011<br>
+#define EALREADY=C2=A0 10114<br>
+#define EBADF=C2=A0 10009<br>
+#define EBADMSG=C2=A0 10074<br>
+#define EBUSY=C2=A0 10016<br>
+#define ECANCELED=C2=A0 10125<br>
+#define ECHILD=C2=A0 10010<br>
+#define ECONNABORTED=C2=A0 10103<br>
+#define ECONNREFUSED=C2=A0 10111<br>
+#define ECONNRESET=C2=A0 10104<br>
+#define EDEADLK=C2=A0 10035<br>
+#define EDESTADDRREQ=C2=A0 10089<br>
+#define EDOM=C2=A0 10033<br>
+#define EEXIST=C2=A0 10017<br>
+#define EFAULT=C2=A0 10014<br>
+#define EFBIG=C2=A0 10027<br>
+#define EHOSTUNREACH=C2=A0 10113<br>
+#define EIDRM=C2=A0 10043<br>
+#define EILSEQ=C2=A0 10084<br>
+#define EINPROGRESS=C2=A0 10115<br>
+#define EINTR=C2=A0 10004<br>
+#define EINVAL=C2=A0 10022<br>
+#define EIO=C2=A0 10005<br>
+#define EISCONN=C2=A0 10106<br>
+#define EISDIR=C2=A0 10021<br>
+#define ELOOP=C2=A0 10040<br>
+#define EMFILE=C2=A0 10024<br>
+#define EMLINK=C2=A0 10031<br>
+#define EMSGSIZE=C2=A0 10090<br>
+#define ENAMETOOLONG=C2=A0 10036<br>
+#define ENETDOWN=C2=A0 10100<br>
+#define ENETRESET=C2=A0 10102<br>
+#define ENETUNREACH=C2=A0 10101<br>
+#define ENFILE=C2=A0 10023<br>
+#define ENOBUFS=C2=A0 10105<br>
+#define ENODEV=C2=A0 10019<br>
+#define ENOENT=C2=A0 10002<br>
+#define ENOEXEC=C2=A0 10008<br>
+#define ENOLCK=C2=A0 10037<br>
+#define ENOLINK=C2=A0 10067<br>
+#define ENOMEM=C2=A0 10012<br>
+#define ENOMSG=C2=A0 10042<br>
+#define ENOPROTOOPT=C2=A0 10092<br>
+#define ENOSPC=C2=A0 10028<br>
+#define ENOSYS=C2=A0 10038<br>
+#define ENOTCONN=C2=A0 10107<br>
+#define ENOTDIR=C2=A0 10020<br>
+#define ENOTEMPTY=C2=A0 10039<br>
+#define ENOTRECOVERABLE=C2=A0 10131<br>
+#define ENOTSOCK=C2=A0 10088<br>
+#define ENOTSUP=C2=A0 10095<br>
+#define ENOTTY=C2=A0 10025<br>
+#define ENXIO=C2=A0 10006<br>
+#define EOPNOTSUPP=C2=A0 10095<br>
+#define EOVERFLOW=C2=A0 10075<br>
+#define EOWNERDEAD=C2=A0 10130<br>
+#define EPERM=C2=A0 10001<br>
+#define EPIPE=C2=A0 10032<br>
+#define EPROTO=C2=A0 10071<br>
+#define EPROTONOSUPPORT=C2=A0 10093<br>
+#define EPROTOTYPE=C2=A0 10091<br>
+#define ERANGE=C2=A0 10034<br>
+#define EROFS=C2=A0 10030<br>
+#define ESPIPE=C2=A0 10029<br>
+#define ESRCH=C2=A0 10003<br>
+#define ETIMEDOUT=C2=A0 10110<br>
+#define ETXTBSY=C2=A0 10026<br>
+#define EWOULDBLOCK=C2=A0 10011<br>
+#define EXDEV=C2=A0 10018<br>
+<br>
+#endif // HOSTED<br>
<br>
=C2=A0#endif<br>
-- <br>
2.55.0<br>
<br>
</blockquote></div></div>
</blockquote></div></div></div>
</blockquote></div></div>

--0000000000009354730658471643--