[Bug libstdc++/80196] fenv_t not declared

[Bug libstdc++/80196] fenv_t not declared

[gr.audio at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80196

Guillaume <gr.audio at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |gr.audio at gmail dot com

--- Comment #7 from Guillaume <gr.audio at gmail dot com> ---
Same problem while trying to build gcc 11.1.0 on Arch Linux (host and target =
Windows).

Configuration:

configure --host=x86_64-w64-mingw32 --target=x86_64-w64-mingw32
--prefix="$PREFIX" --disable-nls --enable-languages=c,c++,ada
--with-pkgversion=GR20210618 --enable-threads=win32 --disable-win32-registry
--disable-multilib --enable-shared --enable-static --disable-sjlj-exceptions
--with-dwarf2

Adding the '--disable-libstdcxx-pch' option doesn't help in my case, same
errors.

The cross-compiler installed on my Arch Linux for building Windows executables
is x86_64-w64-mingw32-gcc.

'x86_64-w64-mingw32-gcc -v' yields:

Utilisation des specs internes.
COLLECT_GCC=x86_64-w64-mingw32-gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-w64-mingw32/11.1.0/lto-wrapper
Cible : x86_64-w64-mingw32
Configuré? avec: /build/mingw-w64-gcc/src/gcc/configure --prefix=/usr
--libexecdir=/usr/lib --target=x86_64-w64-mingw32
--with-bugurl=https://bugs.archlinux.org/
--enable-languages=c,lto,c++,ada,objc,obj-c++,fortran --enable-shared
--enable-static --enable-threads=posix --enable-fully-dynamic-string
--enable-libstdcxx-time=yes --enable-libstdcxx-filesystem-ts=yes
--with-system-zlib --enable-cloog-backend=isl --enable-lto --enable-libgomp
--disable-multilib --enable-checking=release --disable-sjlj-exceptions
--with-dwarf2
Modè?le de thread: posix
Algorithmes de compression LTO supporté?s: zlib zstd
gcc version 11.1.0 (GCC)

[Bug libstdc++/80196] fenv_t not declared

[dilfridge at gentoo dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80196

Andreas K. Huettel <dilfridge at gentoo dot org> changed:

           What    |Removed                     |Added
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                 CC|                            |dilfridge at gentoo dot org

--- Comment #8 from Andreas K. Huettel <dilfridge at gentoo dot org> ---
Created attachment 51076
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51076&action=edit
full build log, xz-compressed

[Bug libstdc++/80196] fenv_t not declared

[dilfridge at gentoo dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80196

--- Comment #9 from Andreas K. Huettel <dilfridge at gentoo dot org> ---
(In reply to Andreas K. Huettel from comment #8)
> Created attachment 51076 [details]
> full build log, xz-compressed

^ Build log for a failure with
 *      --host=riscv32-unknown-linux-gnu 
 *      --target=riscv32-unknown-linux-gnu 
 *      --build=x86_64-pc-linux-gnu 

(Gentoo crossdev build of a native riscv32 compiler)

[Bug libstdc++/80196] fenv_t not declared

[isuruf at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80196

Isuru Fernando <isuruf at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |isuruf at gmail dot com

--- Comment #10 from Isuru Fernando <isuruf at gmail dot com> ---
Failure in gcc 11.1.0 is new and was introduced in
2251b4a5423efa8ee0d7e67537b63e404a1f6afa.

If we are building a canadian cross compiler, then
libstdc++-v3/src/c++17/floating_from_chars.cc will be compiled
with -I<build-dir>/libstdc++-v3/include where fenv.h is.
fenv.h here is the C++ include file which tries to include
the C include file with the same name by using include_next,
but finds the C++ include file from the cross compiler used for
building gcc which becomes empty because of the same include guard
used.

[Bug libstdc++/80196] fenv_t not declared

[gr.audio at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80196

--- Comment #11 from Guillaume <gr.audio at gmail dot com> ---
Thanks! Wasn't happening with previous versions. Is there a workaround?

[Bug libstdc++/80196] fenv_t not declared

[isuruf at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80196

--- Comment #12 from Isuru Fernando <isuruf at gmail dot com> ---
I patched libstdc++-v3/acinclude.m4 to add -nostdinc++ in GLIBCXX_INCLUDES and
it worked for me.

(My previous analysis was wrong. This issue is in canadian cross compilers
where GXX_FOR_TARGET includes its own C++ headers, but with native compilers
GXX_FOR_TARGET is xgcc which doesn't include C++ headers by default)

[Bug libstdc++/80196] fenv_t not declared

[bneumeier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80196

Brett Neumeier <bneumeier at gmail dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |bneumeier at gmail dot com

--- Comment #13 from Brett Neumeier <bneumeier at gmail dot com> ---
I ran into this issue with:

--build=aarch64-unknown-linux-gnu
--host=x86_64-unknown-linux-gnu
--target=x86_64-unknown-linux-gnu


I applied this patch from Yujie Yang, on comment 20 of PR 100017, and it fixed
the issue for me.

diff --git a/configure b/configure
index 6157a8c87fb..2a4a05b4edf 100755
--- a/configure
+++ b/configure
@@ -16653,7 +16653,7 @@ else
 fi


-RAW_CXX_FOR_TARGET="$CXX_FOR_TARGET"
+RAW_CXX_FOR_TARGET="$CXX_FOR_TARGET -nostdinc++"

 { $as_echo "$as_me:${as_lineno-$LINENO}: checking where to find the target ar"
>&5
 $as_echo_n "checking where to find the target ar... " >&6; }
diff --git a/configure.ac b/configure.ac
index 2ff48941754..01ecc8c42d9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3515,7 +3515,7 @@ ACX_CHECK_INSTALLED_TARGET_TOOL(STRIP_FOR_TARGET, strip)
 ACX_CHECK_INSTALLED_TARGET_TOOL(WINDRES_FOR_TARGET, windres)
 ACX_CHECK_INSTALLED_TARGET_TOOL(WINDMC_FOR_TARGET, windmc)

-RAW_CXX_FOR_TARGET="$CXX_FOR_TARGET"
+RAW_CXX_FOR_TARGET="$CXX_FOR_TARGET -nostdinc++"

 GCC_TARGET_TOOL(ar, AR_FOR_TARGET, AR, [binutils/ar])
 GCC_TARGET_TOOL(as, AS_FOR_TARGET, AS, [gas/as-new])

[Bug libstdc++/80196] fenv_t not declared

[gr.audio at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80196

--- Comment #14 from Guillaume <gr.audio at gmail dot com> ---
OK, this patch fixes it for me as well.

[Bug libstdc++/80196] fenv_t not declared

[eddy at klopper dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80196

Eddy L O Jansson <eddy at klopper dot net> changed:

           What    |Removed                     |Added
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                 CC|                            |eddy at klopper dot net

--- Comment #15 from Eddy L O Jansson <eddy at klopper dot net> ---
(In reply to Jonathan Wakely from comment #6)
> Reopening. We still need to know why building the PCH fails to find fenv_t
> for some people.
I ran into this issue doing a very bog-standard build of the newly released GCC
12.1 on linux X86-64, using a configuration that previously successfully built
GCC '12.0.1 20220424 (experimental)' a week or so ago.

I did not save the output from the failed build, but it would eventually fail
with 'error: 'fenv_t' has not been declared in '::' ... '

For reasons that I'll skip, between the successful build of 12.0.1 and now I
had added:

export
CPLUS_INCLUDE_PATH=/opt/local/include/c++/12.0.1:/opt/local/include/c++/12.0.1/x86_64-linux-gnu/

to my .bashrc

Removing the 'CPLUS_INCLUDE_PATH' environment variable made the problem go
away.

[Bug libstdc++/80196] fenv_t not declared

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80196

--- Comment #16 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Eddy L O Jansson from comment #15)
> For reasons that I'll skip, between the successful build of 12.0.1 and now I
> had added:
> 
> export
> CPLUS_INCLUDE_PATH=/opt/local/include/c++/12.0.1:/opt/local/include/c++/12.0.
> 1/x86_64-linux-gnu/
> 
> to my .bashrc

Don't do that. This causes GCC 12.1 to find the headers for GCC 12.0.1 instead
of the libc headers. That breaks the build, but is user error.

[Bug libstdc++/80196] fenv_t not declared

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80196

--- Comment #17 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The problem for canadian crosses (comment 10 onwards) was PR 100017 and is
fixed now.