You are viewing a plain text version of this content. The canonical link for it is here.
Posted to dev@nuttx.apache.org by Anthony Merlino <an...@vergeaero.com> on 2021/01/08 17:57:13 UTC
libcxx and buildroot toolchain
Hey all,
Would someone be willing to share their experience with libcxx and their
toolchain? I've now caught up to the tip of master, which now downloads
and builds libcxx for me instead of using Alan's modified version. I am
facing an issue I've faced before, and would really love to properly
understand how this is supposed to work.
My issues mostly center around libsupc++.a
Currently, my build fails because it can't find libsupc++. From my
understanding, this should be provided by my toolchain. But I am using a
toolchain built by the NuttX buildroot and it does not build the C++
libraries. I am not using RTTI or exceptions, so I don't need what
libsupc++ provides, however the Kconfig option
`[ ] Have libsupc++ (required)`
says, it's required.
What's the right answer here? What are others doing about this?
Is getting NuttX buildroot to build and provide libsupc++.a the *right*
solution?
Do we need to change how libcxx is built in this case?
https://libcxx.llvm.org/docs/BuildingLibcxx.html#using-alternate-abi-libraries
Thank you!
Anthony
Re: libcxx and buildroot toolchain
Posted by Alan Carvalho de Assis <ac...@gmail.com>.
Hi Anthony,
Since Xiang already added support for NuttX on libcxx mainstream:
https://reviews.llvm.org/D88718?id=303700
I think it is time to phase out my libcxx repository and we will stick
to libcxx mainline.
Do you agree on that?
BR,
Alan
On 1/9/21, Anthony Merlino <an...@vergeaero.com> wrote:
> Thanks for the info Xiang! I was on the right track but it is good to have
> some affirmation that I'm not missing something.
>
> The issue with the Arm maintained toolchain, as Greg has warned many times,
> is its use of newlib. Are you doing anything to ensure the wrong math
> library is not used?
>
> I will work on improving buildroot to also build and include libsupcxx.a.
>
> With Alan's modified version of libcxx, he disabled some exception logic
> and maybe some other logic that was allowing me to build without libsupxx.a
> entirely.
>
> Also, may I ask why we are building libcxx by manually grabbing the source
> files and building it? Are we against just driving the build from their
> existing build system? I ask because there are options in the way libcxx is
> built that might be useful to us and we have to replicate all of that if we
> just grab the source.
>
>
> Best,
> Anthony
>
>
> On Sat, Jan 9, 2021, 7:32 AM Xiang Xiao <xi...@gmail.com> wrote:
>
>> On Fri, Jan 8, 2021 at 9:57 AM Anthony Merlino <an...@vergeaero.com>
>> wrote:
>>
>> > Hey all,
>> >
>> > Would someone be willing to share their experience with libcxx and
>> > their
>> > toolchain?
>>
>>
>> This toolchain should work:
>>
>> https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-rm
>>
>>
>> > I've now caught up to the tip of master, which now downloads
>> > and builds libcxx for me instead of using Alan's modified version. I am
>> > facing an issue I've faced before, and would really love to properly
>> > understand how this is supposed to work.
>> >
>> > My issues mostly center around libsupc++.a
>> >
>> > Currently, my build fails because it can't find libsupc++. From my
>> > understanding, this should be provided by my toolchain. But I am using
>> > a
>> > toolchain built by the NuttX buildroot and it does not build the C++
>> > libraries. I am not using RTTI or exceptions, so I don't need what
>> >
>>
>> libsupc++.a doesn't only provide RTTI and exectpions, but also provide
>> some
>> basic functions called by compiler:
>>
>> https://github.com/gcc-mirror/gcc/tree/master/libstdc%2B%2B-v3/libsupc%2B%2B
>>
>> libsupc++ provides, however the Kconfig option
>> > `[ ] Have libsupc++ (required)`
>> > says, it's required.
>> >
>> > What's the right answer here? What are others doing about this?
>> >
>> >
>> Three methods you can try:
>>
>> 1. Switch to the ARM maintained toolchain
>> 2. Build libsupc++.a for NuttX toolchain
>> 3. Enhance NuttX's libc++ runtime support
>>
>>
>> https://github.com/apache/incubator-nuttx/tree/master/libs/libxx
>>
>>
>> > Is getting NuttX buildroot to build and provide libsupc++.a the *right*
>> > solution?
>> >
>> >
>> Yes, a complete toolchain should provide libsupc++.a. libsupc++.a just
>> like
>> libgcc.a should part of toolchain, not part of c/c++ library
>> implemetnation, because libsupc++.a tightly couple with the implementaion
>> detail of compiler.
>>
>>
>> > Do we need to change how libcxx is built in this case?
>> >
>> >
>> https://libcxx.llvm.org/docs/BuildingLibcxx.html#using-alternate-abi-libraries
>> >
>> >
>> Then you need port the libcxxrt:
>> https://github.com/libcxxrt/libcxxrt
>>
>>
>> > Thank you!
>> >
>> > Anthony
>> >
>>
>
Re: libcxx and buildroot toolchain
Posted by Anthony Merlino <an...@vergeaero.com>.
Thanks for confirming your setup is working. I've checked my linker script
and it does have the ARM.exidx and ARM.extab sections.
I have to assume this is due to some libcxxabi/libgcc issue, but who knows.
I'm open to suggestions.
On Wed, Jan 13, 2021 at 1:59 AM Xiang Xiao <xi...@gmail.com>
wrote:
> On Wed, Jan 13, 2021 at 12:44 AM Anthony Merlino <an...@vergeaero.com>
> wrote:
>
> > >
> > > Since Xiang already added support for NuttX on libcxx mainstream:
> > > https://reviews.llvm.org/D88718?id=303700
> > >
> > > I think it is time to phase out my libcxx repository and we will stick
> > > to libcxx mainline.
> > >
> > > Do you agree on that?
> >
> >
> > In general, yes. However, with your modified version, I was able to build
> > and use libcxx without libsupc++ at all. With the upstream version,
> > libsupc++ is required. I'm still not sure how I was able to get away
> > without this before.
> >
> > It seems building libsupc++.a is not the easiest. The gcc build system
> is a
> > complicated beast.
> >
> > Instead, I have added support for building the libcxxabi library
> alongside
> > libcxx. I have now successfully gotten it to build and run, but exception
> > unwinding does not work.
> >
> > Xiang, are you actually using exceptions? Can you confirm whether
> exception
> > unwinding is actually working for you with gcc and libsupc++.a?
> >
> >
> Yes, the exception can work as expect, I just try cxxtest with
> CONFIG_CXX_EXCEPTION:
> https://github.com/apache/incubator-nuttx-apps/tree/master/testing/cxxtest
> Here is the output from a board with Cortex M33:
> test ofstream=========================== printf: Starting test_ostream
> printf:
> Successfully opened /dev/console cout: Successfully opened /dev/console
> Writing
> this to /dev/console test iostream=========================== Hello, this
> is only a test Print an int: 190 Print a char: d test
> vector============================= v1=1 2 3 Hello World Good Luck test
> map================================ test
> rtti===============================
> extend test exception========================== Catch exception: runtime
> error
> The simulator has the same output too.
> BTW, to make the exception work, the link script need .ARM.extab
> and.ARM.exidx sections:
> .ARM.extab : ALIGN(4) {
> *(.ARM.extab*)
> } > ROM
>
> .ARM.exidx : ALIGN(4) {
> __exidx_start = ABSOLUTE(.);
> *(.ARM.exidx*)
> __exidx_end = ABSOLUTE(.);
> } > ROM
>
>
> > Best,
> > Anthony
> >
> >
> >
> >
> >
> > On Sat, Jan 9, 2021 at 11:57 AM Xiang Xiao <xi...@gmail.com>
> > wrote:
> >
> > > On Sat, Jan 9, 2021 at 8:11 AM Anthony Merlino <an...@vergeaero.com>
> > > wrote:
> > >
> > > > Thanks for the info Xiang! I was on the right track but it is good to
> > > have
> > > > some affirmation that I'm not missing something.
> > > >
> > > > The issue with the Arm maintained toolchain, as Greg has warned many
> > > times,
> > > > is its use of newlib. Are you doing anything to ensure the wrong math
> > > > library is not used?
> > > >
> > > >
> > > Yes, from the theory, the potential conflict may happen since NuttX has
> > its
> > > own libc/libm implementation which is totally different from newlib,
> but
> > at
> > > least the follow combination is good from the practice:
> > >
> > > 1. libc and libm come from NuttX, libsupc++ come from newlib
> > > 2. libc come from NuttX, libm and libsupc++ come from newlib
> > >
> > > We use item 2 for all arm based products and sim develop environment.
> > >
> > > I will work on improving buildroot to also build and include
> libsupcxx.a.
> > > >
> > > > With Alan's modified version of libcxx, he disabled some exception
> > logic
> > > > and maybe some other logic that was allowing me to build without
> > > libsupxx.a
> > > > entirely.
> > > >
> > > >
> > > libcxx will turn on/off exception and rtti automatically, you just need
> > > specify the right compiler flag(e.g. -fno-exceptions and -fno-rtti):
> > >
> > >
> >
> https://github.com/llvm/llvm-project/blob/main/libcxx/include/__config#L433-L435
> > >
> > >
> >
> https://github.com/llvm/llvm-project/blob/main/libcxx/include/__config#L1092-L1098
> > >
> > >
> > > > Also, may I ask why we are building libcxx by manually grabbing the
> > > source
> > > > files and building it? Are we against just driving the build from
> their
> > > > existing build system?
> > >
> > >
> > > libcxx uses CMake, it's hard to integrate their build system. But, it
> > will
> > > be great if we can find a clean solution to reuse their build script.
> > >
> > >
> > > > I ask because there are options in the way libcxx is
> > > > built that might be useful to us and we have to replicate all of that
> > if
> > > we
> > > > just grab the source.
> > > >
> > > >
> > > Except the build system integration, all NuttX specific changes are
> > > upstream to the llvm project. We have to apply the following patches:
> > >
> > >
> >
> https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libc-Fix-a-few-warnings.patch
> > >
> > >
> >
> https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libc-Fix-tests-failing-with-Clang-after-removing-GCC.patch
> > >
> > >
> >
> https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libc-NFC-Fix-several-GCC-warnings-in-the-test-suite.patch
> > >
> > >
> >
> https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libcxx-Check-_LIBCPP_PROVIDES_DEFAULT_RUNE_TABLE-fir.patch
> > >
> > >
> >
> https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libcxx-Port-to-NuttX-https-nuttx.apache.org-RTOS.patch
> > > just because the new libcxx contains our change doesn't release yet.
> Once
> > > the new release is out, I will remove all patches from the NuttX repo.
> > >
> > >
> > > >
> > > > Best,
> > > > Anthony
> > > >
> > > >
> > > > On Sat, Jan 9, 2021, 7:32 AM Xiang Xiao <xi...@gmail.com>
> > > wrote:
> > > >
> > > > > On Fri, Jan 8, 2021 at 9:57 AM Anthony Merlino <
> > anthony@vergeaero.com>
> > > > > wrote:
> > > > >
> > > > > > Hey all,
> > > > > >
> > > > > > Would someone be willing to share their experience with libcxx
> and
> > > > their
> > > > > > toolchain?
> > > > >
> > > > >
> > > > > This toolchain should work:
> > > > >
> > > > >
> > > >
> > >
> >
> https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-rm
> > > > >
> > > > >
> > > > > > I've now caught up to the tip of master, which now downloads
> > > > > > and builds libcxx for me instead of using Alan's modified
> version.
> > I
> > > am
> > > > > > facing an issue I've faced before, and would really love to
> > properly
> > > > > > understand how this is supposed to work.
> > > > > >
> > > > > > My issues mostly center around libsupc++.a
> > > > > >
> > > > > > Currently, my build fails because it can't find libsupc++. From
> my
> > > > > > understanding, this should be provided by my toolchain. But I am
> > > using
> > > > a
> > > > > > toolchain built by the NuttX buildroot and it does not build the
> > C++
> > > > > > libraries. I am not using RTTI or exceptions, so I don't need
> what
> > > > > >
> > > > >
> > > > > libsupc++.a doesn't only provide RTTI and exectpions, but also
> > provide
> > > > some
> > > > > basic functions called by compiler:
> > > > >
> > > > >
> > > >
> > >
> >
> https://github.com/gcc-mirror/gcc/tree/master/libstdc%2B%2B-v3/libsupc%2B%2B
> > > > >
> > > > > libsupc++ provides, however the Kconfig option
> > > > > > `[ ] Have libsupc++ (required)`
> > > > > > says, it's required.
> > > > > >
> > > > > > What's the right answer here? What are others doing about this?
> > > > > >
> > > > > >
> > > > > Three methods you can try:
> > > > >
> > > > > 1. Switch to the ARM maintained toolchain
> > > > > 2. Build libsupc++.a for NuttX toolchain
> > > > > 3. Enhance NuttX's libc++ runtime support
> > > > >
> > > > >
> > > > > https://github.com/apache/incubator-nuttx/tree/master/libs/libxx
> > > > >
> > > > >
> > > > > > Is getting NuttX buildroot to build and provide libsupc++.a the
> > > *right*
> > > > > > solution?
> > > > > >
> > > > > >
> > > > > Yes, a complete toolchain should provide libsupc++.a. libsupc++.a
> > just
> > > > like
> > > > > libgcc.a should part of toolchain, not part of c/c++ library
> > > > > implemetnation, because libsupc++.a tightly couple with the
> > > implementaion
> > > > > detail of compiler.
> > > > >
> > > > >
> > > > > > Do we need to change how libcxx is built in this case?
> > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
> https://libcxx.llvm.org/docs/BuildingLibcxx.html#using-alternate-abi-libraries
> > > > > >
> > > > > >
> > > > > Then you need port the libcxxrt:
> > > > > https://github.com/libcxxrt/libcxxrt
> > > > >
> > > > >
> > > > > > Thank you!
> > > > > >
> > > > > > Anthony
> > > > > >
> > > > >
> > > >
> > >
> >
>
Re: libcxx and buildroot toolchain
Posted by Xiang Xiao <xi...@gmail.com>.
On Wed, Jan 13, 2021 at 12:44 AM Anthony Merlino <an...@vergeaero.com>
wrote:
> >
> > Since Xiang already added support for NuttX on libcxx mainstream:
> > https://reviews.llvm.org/D88718?id=303700
> >
> > I think it is time to phase out my libcxx repository and we will stick
> > to libcxx mainline.
> >
> > Do you agree on that?
>
>
> In general, yes. However, with your modified version, I was able to build
> and use libcxx without libsupc++ at all. With the upstream version,
> libsupc++ is required. I'm still not sure how I was able to get away
> without this before.
>
> It seems building libsupc++.a is not the easiest. The gcc build system is a
> complicated beast.
>
> Instead, I have added support for building the libcxxabi library alongside
> libcxx. I have now successfully gotten it to build and run, but exception
> unwinding does not work.
>
> Xiang, are you actually using exceptions? Can you confirm whether exception
> unwinding is actually working for you with gcc and libsupc++.a?
>
>
Yes, the exception can work as expect, I just try cxxtest with
CONFIG_CXX_EXCEPTION:
https://github.com/apache/incubator-nuttx-apps/tree/master/testing/cxxtest
Here is the output from a board with Cortex M33:
test ofstream=========================== printf: Starting test_ostream printf:
Successfully opened /dev/console cout: Successfully opened /dev/console Writing
this to /dev/console test iostream=========================== Hello, this
is only a test Print an int: 190 Print a char: d test
vector============================= v1=1 2 3 Hello World Good Luck test
map================================ test rtti===============================
extend test exception========================== Catch exception: runtime
error
The simulator has the same output too.
BTW, to make the exception work, the link script need .ARM.extab
and.ARM.exidx sections:
.ARM.extab : ALIGN(4) {
*(.ARM.extab*)
} > ROM
.ARM.exidx : ALIGN(4) {
__exidx_start = ABSOLUTE(.);
*(.ARM.exidx*)
__exidx_end = ABSOLUTE(.);
} > ROM
> Best,
> Anthony
>
>
>
>
>
> On Sat, Jan 9, 2021 at 11:57 AM Xiang Xiao <xi...@gmail.com>
> wrote:
>
> > On Sat, Jan 9, 2021 at 8:11 AM Anthony Merlino <an...@vergeaero.com>
> > wrote:
> >
> > > Thanks for the info Xiang! I was on the right track but it is good to
> > have
> > > some affirmation that I'm not missing something.
> > >
> > > The issue with the Arm maintained toolchain, as Greg has warned many
> > times,
> > > is its use of newlib. Are you doing anything to ensure the wrong math
> > > library is not used?
> > >
> > >
> > Yes, from the theory, the potential conflict may happen since NuttX has
> its
> > own libc/libm implementation which is totally different from newlib, but
> at
> > least the follow combination is good from the practice:
> >
> > 1. libc and libm come from NuttX, libsupc++ come from newlib
> > 2. libc come from NuttX, libm and libsupc++ come from newlib
> >
> > We use item 2 for all arm based products and sim develop environment.
> >
> > I will work on improving buildroot to also build and include libsupcxx.a.
> > >
> > > With Alan's modified version of libcxx, he disabled some exception
> logic
> > > and maybe some other logic that was allowing me to build without
> > libsupxx.a
> > > entirely.
> > >
> > >
> > libcxx will turn on/off exception and rtti automatically, you just need
> > specify the right compiler flag(e.g. -fno-exceptions and -fno-rtti):
> >
> >
> https://github.com/llvm/llvm-project/blob/main/libcxx/include/__config#L433-L435
> >
> >
> https://github.com/llvm/llvm-project/blob/main/libcxx/include/__config#L1092-L1098
> >
> >
> > > Also, may I ask why we are building libcxx by manually grabbing the
> > source
> > > files and building it? Are we against just driving the build from their
> > > existing build system?
> >
> >
> > libcxx uses CMake, it's hard to integrate their build system. But, it
> will
> > be great if we can find a clean solution to reuse their build script.
> >
> >
> > > I ask because there are options in the way libcxx is
> > > built that might be useful to us and we have to replicate all of that
> if
> > we
> > > just grab the source.
> > >
> > >
> > Except the build system integration, all NuttX specific changes are
> > upstream to the llvm project. We have to apply the following patches:
> >
> >
> https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libc-Fix-a-few-warnings.patch
> >
> >
> https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libc-Fix-tests-failing-with-Clang-after-removing-GCC.patch
> >
> >
> https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libc-NFC-Fix-several-GCC-warnings-in-the-test-suite.patch
> >
> >
> https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libcxx-Check-_LIBCPP_PROVIDES_DEFAULT_RUNE_TABLE-fir.patch
> >
> >
> https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libcxx-Port-to-NuttX-https-nuttx.apache.org-RTOS.patch
> > just because the new libcxx contains our change doesn't release yet. Once
> > the new release is out, I will remove all patches from the NuttX repo.
> >
> >
> > >
> > > Best,
> > > Anthony
> > >
> > >
> > > On Sat, Jan 9, 2021, 7:32 AM Xiang Xiao <xi...@gmail.com>
> > wrote:
> > >
> > > > On Fri, Jan 8, 2021 at 9:57 AM Anthony Merlino <
> anthony@vergeaero.com>
> > > > wrote:
> > > >
> > > > > Hey all,
> > > > >
> > > > > Would someone be willing to share their experience with libcxx and
> > > their
> > > > > toolchain?
> > > >
> > > >
> > > > This toolchain should work:
> > > >
> > > >
> > >
> >
> https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-rm
> > > >
> > > >
> > > > > I've now caught up to the tip of master, which now downloads
> > > > > and builds libcxx for me instead of using Alan's modified version.
> I
> > am
> > > > > facing an issue I've faced before, and would really love to
> properly
> > > > > understand how this is supposed to work.
> > > > >
> > > > > My issues mostly center around libsupc++.a
> > > > >
> > > > > Currently, my build fails because it can't find libsupc++. From my
> > > > > understanding, this should be provided by my toolchain. But I am
> > using
> > > a
> > > > > toolchain built by the NuttX buildroot and it does not build the
> C++
> > > > > libraries. I am not using RTTI or exceptions, so I don't need what
> > > > >
> > > >
> > > > libsupc++.a doesn't only provide RTTI and exectpions, but also
> provide
> > > some
> > > > basic functions called by compiler:
> > > >
> > > >
> > >
> >
> https://github.com/gcc-mirror/gcc/tree/master/libstdc%2B%2B-v3/libsupc%2B%2B
> > > >
> > > > libsupc++ provides, however the Kconfig option
> > > > > `[ ] Have libsupc++ (required)`
> > > > > says, it's required.
> > > > >
> > > > > What's the right answer here? What are others doing about this?
> > > > >
> > > > >
> > > > Three methods you can try:
> > > >
> > > > 1. Switch to the ARM maintained toolchain
> > > > 2. Build libsupc++.a for NuttX toolchain
> > > > 3. Enhance NuttX's libc++ runtime support
> > > >
> > > >
> > > > https://github.com/apache/incubator-nuttx/tree/master/libs/libxx
> > > >
> > > >
> > > > > Is getting NuttX buildroot to build and provide libsupc++.a the
> > *right*
> > > > > solution?
> > > > >
> > > > >
> > > > Yes, a complete toolchain should provide libsupc++.a. libsupc++.a
> just
> > > like
> > > > libgcc.a should part of toolchain, not part of c/c++ library
> > > > implemetnation, because libsupc++.a tightly couple with the
> > implementaion
> > > > detail of compiler.
> > > >
> > > >
> > > > > Do we need to change how libcxx is built in this case?
> > > > >
> > > > >
> > > >
> > >
> >
> https://libcxx.llvm.org/docs/BuildingLibcxx.html#using-alternate-abi-libraries
> > > > >
> > > > >
> > > > Then you need port the libcxxrt:
> > > > https://github.com/libcxxrt/libcxxrt
> > > >
> > > >
> > > > > Thank you!
> > > > >
> > > > > Anthony
> > > > >
> > > >
> > >
> >
>
Re: libcxx and buildroot toolchain
Posted by Alan Carvalho de Assis <ac...@gmail.com>.
Hi Anthony,
On 1/12/21, Anthony Merlino <an...@vergeaero.com> wrote:
>>
>> Since Xiang already added support for NuttX on libcxx mainstream:
>> https://reviews.llvm.org/D88718?id=303700
>>
>> I think it is time to phase out my libcxx repository and we will stick
>> to libcxx mainline.
>>
>> Do you agree on that?
>
>
> In general, yes. However, with your modified version, I was able to build
> and use libcxx without libsupc++ at all. With the upstream version,
> libsupc++ is required. I'm still not sure how I was able to get away
> without this before.
>
> It seems building libsupc++.a is not the easiest. The gcc build system is a
> complicated beast.
>
> Instead, I have added support for building the libcxxabi library alongside
> libcxx. I have now successfully gotten it to build and run, but exception
> unwinding does not work.
>
Ok, let's to keep it for a while until we have everything working with
LLVM libcxx from mainline.
BR,
Alan
Re: libcxx and buildroot toolchain
Posted by Anthony Merlino <an...@vergeaero.com>.
>
> Since Xiang already added support for NuttX on libcxx mainstream:
> https://reviews.llvm.org/D88718?id=303700
>
> I think it is time to phase out my libcxx repository and we will stick
> to libcxx mainline.
>
> Do you agree on that?
In general, yes. However, with your modified version, I was able to build
and use libcxx without libsupc++ at all. With the upstream version,
libsupc++ is required. I'm still not sure how I was able to get away
without this before.
It seems building libsupc++.a is not the easiest. The gcc build system is a
complicated beast.
Instead, I have added support for building the libcxxabi library alongside
libcxx. I have now successfully gotten it to build and run, but exception
unwinding does not work.
Xiang, are you actually using exceptions? Can you confirm whether exception
unwinding is actually working for you with gcc and libsupc++.a?
Best,
Anthony
On Sat, Jan 9, 2021 at 11:57 AM Xiang Xiao <xi...@gmail.com>
wrote:
> On Sat, Jan 9, 2021 at 8:11 AM Anthony Merlino <an...@vergeaero.com>
> wrote:
>
> > Thanks for the info Xiang! I was on the right track but it is good to
> have
> > some affirmation that I'm not missing something.
> >
> > The issue with the Arm maintained toolchain, as Greg has warned many
> times,
> > is its use of newlib. Are you doing anything to ensure the wrong math
> > library is not used?
> >
> >
> Yes, from the theory, the potential conflict may happen since NuttX has its
> own libc/libm implementation which is totally different from newlib, but at
> least the follow combination is good from the practice:
>
> 1. libc and libm come from NuttX, libsupc++ come from newlib
> 2. libc come from NuttX, libm and libsupc++ come from newlib
>
> We use item 2 for all arm based products and sim develop environment.
>
> I will work on improving buildroot to also build and include libsupcxx.a.
> >
> > With Alan's modified version of libcxx, he disabled some exception logic
> > and maybe some other logic that was allowing me to build without
> libsupxx.a
> > entirely.
> >
> >
> libcxx will turn on/off exception and rtti automatically, you just need
> specify the right compiler flag(e.g. -fno-exceptions and -fno-rtti):
>
> https://github.com/llvm/llvm-project/blob/main/libcxx/include/__config#L433-L435
>
> https://github.com/llvm/llvm-project/blob/main/libcxx/include/__config#L1092-L1098
>
>
> > Also, may I ask why we are building libcxx by manually grabbing the
> source
> > files and building it? Are we against just driving the build from their
> > existing build system?
>
>
> libcxx uses CMake, it's hard to integrate their build system. But, it will
> be great if we can find a clean solution to reuse their build script.
>
>
> > I ask because there are options in the way libcxx is
> > built that might be useful to us and we have to replicate all of that if
> we
> > just grab the source.
> >
> >
> Except the build system integration, all NuttX specific changes are
> upstream to the llvm project. We have to apply the following patches:
>
> https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libc-Fix-a-few-warnings.patch
>
> https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libc-Fix-tests-failing-with-Clang-after-removing-GCC.patch
>
> https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libc-NFC-Fix-several-GCC-warnings-in-the-test-suite.patch
>
> https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libcxx-Check-_LIBCPP_PROVIDES_DEFAULT_RUNE_TABLE-fir.patch
>
> https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libcxx-Port-to-NuttX-https-nuttx.apache.org-RTOS.patch
> just because the new libcxx contains our change doesn't release yet. Once
> the new release is out, I will remove all patches from the NuttX repo.
>
>
> >
> > Best,
> > Anthony
> >
> >
> > On Sat, Jan 9, 2021, 7:32 AM Xiang Xiao <xi...@gmail.com>
> wrote:
> >
> > > On Fri, Jan 8, 2021 at 9:57 AM Anthony Merlino <an...@vergeaero.com>
> > > wrote:
> > >
> > > > Hey all,
> > > >
> > > > Would someone be willing to share their experience with libcxx and
> > their
> > > > toolchain?
> > >
> > >
> > > This toolchain should work:
> > >
> > >
> >
> https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-rm
> > >
> > >
> > > > I've now caught up to the tip of master, which now downloads
> > > > and builds libcxx for me instead of using Alan's modified version. I
> am
> > > > facing an issue I've faced before, and would really love to properly
> > > > understand how this is supposed to work.
> > > >
> > > > My issues mostly center around libsupc++.a
> > > >
> > > > Currently, my build fails because it can't find libsupc++. From my
> > > > understanding, this should be provided by my toolchain. But I am
> using
> > a
> > > > toolchain built by the NuttX buildroot and it does not build the C++
> > > > libraries. I am not using RTTI or exceptions, so I don't need what
> > > >
> > >
> > > libsupc++.a doesn't only provide RTTI and exectpions, but also provide
> > some
> > > basic functions called by compiler:
> > >
> > >
> >
> https://github.com/gcc-mirror/gcc/tree/master/libstdc%2B%2B-v3/libsupc%2B%2B
> > >
> > > libsupc++ provides, however the Kconfig option
> > > > `[ ] Have libsupc++ (required)`
> > > > says, it's required.
> > > >
> > > > What's the right answer here? What are others doing about this?
> > > >
> > > >
> > > Three methods you can try:
> > >
> > > 1. Switch to the ARM maintained toolchain
> > > 2. Build libsupc++.a for NuttX toolchain
> > > 3. Enhance NuttX's libc++ runtime support
> > >
> > >
> > > https://github.com/apache/incubator-nuttx/tree/master/libs/libxx
> > >
> > >
> > > > Is getting NuttX buildroot to build and provide libsupc++.a the
> *right*
> > > > solution?
> > > >
> > > >
> > > Yes, a complete toolchain should provide libsupc++.a. libsupc++.a just
> > like
> > > libgcc.a should part of toolchain, not part of c/c++ library
> > > implemetnation, because libsupc++.a tightly couple with the
> implementaion
> > > detail of compiler.
> > >
> > >
> > > > Do we need to change how libcxx is built in this case?
> > > >
> > > >
> > >
> >
> https://libcxx.llvm.org/docs/BuildingLibcxx.html#using-alternate-abi-libraries
> > > >
> > > >
> > > Then you need port the libcxxrt:
> > > https://github.com/libcxxrt/libcxxrt
> > >
> > >
> > > > Thank you!
> > > >
> > > > Anthony
> > > >
> > >
> >
>
Re: libcxx and buildroot toolchain
Posted by Gregory Nutt <sp...@gmail.com>.
> Is NuttX’ buildroot been adopted into Apache along with NuttX? I looked for it, but couldn’t find it. I have a few updates to push (gcc 8.4, 9, 10). I’d really like to share these…
No. It can't come into the Apache repository because it is GPL (at
least not without some special consideration). It is still in the same
location in the Bitbucket repository:
https://bitbucket.org/nuttx/buildroot/src/master/
Re: libcxx and buildroot toolchain
Posted by "David S. Alessio" <da...@gmail.com>.
Slightly off topic, but related:
Is NuttX’ buildroot been adopted into Apache along with NuttX? I looked for it, but couldn’t find it. I have a few updates to push (gcc 8.4, 9, 10). I’d really like to share these…
Regards,
-david
> On Jan 9, 2021, at 8:57 AM, Xiang Xiao <xi...@gmail.com> wrote:
>
> On Sat, Jan 9, 2021 at 8:11 AM Anthony Merlino <an...@vergeaero.com>
> wrote:
>
>> Thanks for the info Xiang! I was on the right track but it is good to have
>> some affirmation that I'm not missing something.
>>
>> The issue with the Arm maintained toolchain, as Greg has warned many times,
>> is its use of newlib. Are you doing anything to ensure the wrong math
>> library is not used?
>>
>>
> Yes, from the theory, the potential conflict may happen since NuttX has its
> own libc/libm implementation which is totally different from newlib, but at
> least the follow combination is good from the practice:
>
> 1. libc and libm come from NuttX, libsupc++ come from newlib
> 2. libc come from NuttX, libm and libsupc++ come from newlib
>
> We use item 2 for all arm based products and sim develop environment.
>
> I will work on improving buildroot to also build and include libsupcxx.a.
>>
>> With Alan's modified version of libcxx, he disabled some exception logic
>> and maybe some other logic that was allowing me to build without libsupxx.a
>> entirely.
>>
>>
> libcxx will turn on/off exception and rtti automatically, you just need
> specify the right compiler flag(e.g. -fno-exceptions and -fno-rtti):
> https://github.com/llvm/llvm-project/blob/main/libcxx/include/__config#L433-L435
> https://github.com/llvm/llvm-project/blob/main/libcxx/include/__config#L1092-L1098
>
>
>> Also, may I ask why we are building libcxx by manually grabbing the source
>> files and building it? Are we against just driving the build from their
>> existing build system?
>
>
> libcxx uses CMake, it's hard to integrate their build system. But, it will
> be great if we can find a clean solution to reuse their build script.
>
>
>> I ask because there are options in the way libcxx is
>> built that might be useful to us and we have to replicate all of that if we
>> just grab the source.
>>
>>
> Except the build system integration, all NuttX specific changes are
> upstream to the llvm project. We have to apply the following patches:
> https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libc-Fix-a-few-warnings.patch
> https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libc-Fix-tests-failing-with-Clang-after-removing-GCC.patch
> https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libc-NFC-Fix-several-GCC-warnings-in-the-test-suite.patch
> https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libcxx-Check-_LIBCPP_PROVIDES_DEFAULT_RUNE_TABLE-fir.patch
> https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libcxx-Port-to-NuttX-https-nuttx.apache.org-RTOS.patch
> just because the new libcxx contains our change doesn't release yet. Once
> the new release is out, I will remove all patches from the NuttX repo.
>
>
>>
>> Best,
>> Anthony
>>
>>
>> On Sat, Jan 9, 2021, 7:32 AM Xiang Xiao <xi...@gmail.com> wrote:
>>
>>> On Fri, Jan 8, 2021 at 9:57 AM Anthony Merlino <an...@vergeaero.com>
>>> wrote:
>>>
>>>> Hey all,
>>>>
>>>> Would someone be willing to share their experience with libcxx and
>> their
>>>> toolchain?
>>>
>>>
>>> This toolchain should work:
>>>
>>>
>> https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-rm
>>>
>>>
>>>> I've now caught up to the tip of master, which now downloads
>>>> and builds libcxx for me instead of using Alan's modified version. I am
>>>> facing an issue I've faced before, and would really love to properly
>>>> understand how this is supposed to work.
>>>>
>>>> My issues mostly center around libsupc++.a
>>>>
>>>> Currently, my build fails because it can't find libsupc++. From my
>>>> understanding, this should be provided by my toolchain. But I am using
>> a
>>>> toolchain built by the NuttX buildroot and it does not build the C++
>>>> libraries. I am not using RTTI or exceptions, so I don't need what
>>>>
>>>
>>> libsupc++.a doesn't only provide RTTI and exectpions, but also provide
>> some
>>> basic functions called by compiler:
>>>
>>>
>> https://github.com/gcc-mirror/gcc/tree/master/libstdc%2B%2B-v3/libsupc%2B%2B
>>>
>>> libsupc++ provides, however the Kconfig option
>>>> `[ ] Have libsupc++ (required)`
>>>> says, it's required.
>>>>
>>>> What's the right answer here? What are others doing about this?
>>>>
>>>>
>>> Three methods you can try:
>>>
>>> 1. Switch to the ARM maintained toolchain
>>> 2. Build libsupc++.a for NuttX toolchain
>>> 3. Enhance NuttX's libc++ runtime support
>>>
>>>
>>> https://github.com/apache/incubator-nuttx/tree/master/libs/libxx
>>>
>>>
>>>> Is getting NuttX buildroot to build and provide libsupc++.a the *right*
>>>> solution?
>>>>
>>>>
>>> Yes, a complete toolchain should provide libsupc++.a. libsupc++.a just
>> like
>>> libgcc.a should part of toolchain, not part of c/c++ library
>>> implemetnation, because libsupc++.a tightly couple with the implementaion
>>> detail of compiler.
>>>
>>>
>>>> Do we need to change how libcxx is built in this case?
>>>>
>>>>
>>>
>> https://libcxx.llvm.org/docs/BuildingLibcxx.html#using-alternate-abi-libraries
>>>>
>>>>
>>> Then you need port the libcxxrt:
>>> https://github.com/libcxxrt/libcxxrt
>>>
>>>
>>>> Thank you!
>>>>
>>>> Anthony
>>>>
>>>
>>
Re: libcxx and buildroot toolchain
Posted by Xiang Xiao <xi...@gmail.com>.
On Sat, Jan 9, 2021 at 8:11 AM Anthony Merlino <an...@vergeaero.com>
wrote:
> Thanks for the info Xiang! I was on the right track but it is good to have
> some affirmation that I'm not missing something.
>
> The issue with the Arm maintained toolchain, as Greg has warned many times,
> is its use of newlib. Are you doing anything to ensure the wrong math
> library is not used?
>
>
Yes, from the theory, the potential conflict may happen since NuttX has its
own libc/libm implementation which is totally different from newlib, but at
least the follow combination is good from the practice:
1. libc and libm come from NuttX, libsupc++ come from newlib
2. libc come from NuttX, libm and libsupc++ come from newlib
We use item 2 for all arm based products and sim develop environment.
I will work on improving buildroot to also build and include libsupcxx.a.
>
> With Alan's modified version of libcxx, he disabled some exception logic
> and maybe some other logic that was allowing me to build without libsupxx.a
> entirely.
>
>
libcxx will turn on/off exception and rtti automatically, you just need
specify the right compiler flag(e.g. -fno-exceptions and -fno-rtti):
https://github.com/llvm/llvm-project/blob/main/libcxx/include/__config#L433-L435
https://github.com/llvm/llvm-project/blob/main/libcxx/include/__config#L1092-L1098
> Also, may I ask why we are building libcxx by manually grabbing the source
> files and building it? Are we against just driving the build from their
> existing build system?
libcxx uses CMake, it's hard to integrate their build system. But, it will
be great if we can find a clean solution to reuse their build script.
> I ask because there are options in the way libcxx is
> built that might be useful to us and we have to replicate all of that if we
> just grab the source.
>
>
Except the build system integration, all NuttX specific changes are
upstream to the llvm project. We have to apply the following patches:
https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libc-Fix-a-few-warnings.patch
https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libc-Fix-tests-failing-with-Clang-after-removing-GCC.patch
https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libc-NFC-Fix-several-GCC-warnings-in-the-test-suite.patch
https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libcxx-Check-_LIBCPP_PROVIDES_DEFAULT_RUNE_TABLE-fir.patch
https://github.com/apache/incubator-nuttx/blob/master/libs/libxx/0001-libcxx-Port-to-NuttX-https-nuttx.apache.org-RTOS.patch
just because the new libcxx contains our change doesn't release yet. Once
the new release is out, I will remove all patches from the NuttX repo.
>
> Best,
> Anthony
>
>
> On Sat, Jan 9, 2021, 7:32 AM Xiang Xiao <xi...@gmail.com> wrote:
>
> > On Fri, Jan 8, 2021 at 9:57 AM Anthony Merlino <an...@vergeaero.com>
> > wrote:
> >
> > > Hey all,
> > >
> > > Would someone be willing to share their experience with libcxx and
> their
> > > toolchain?
> >
> >
> > This toolchain should work:
> >
> >
> https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-rm
> >
> >
> > > I've now caught up to the tip of master, which now downloads
> > > and builds libcxx for me instead of using Alan's modified version. I am
> > > facing an issue I've faced before, and would really love to properly
> > > understand how this is supposed to work.
> > >
> > > My issues mostly center around libsupc++.a
> > >
> > > Currently, my build fails because it can't find libsupc++. From my
> > > understanding, this should be provided by my toolchain. But I am using
> a
> > > toolchain built by the NuttX buildroot and it does not build the C++
> > > libraries. I am not using RTTI or exceptions, so I don't need what
> > >
> >
> > libsupc++.a doesn't only provide RTTI and exectpions, but also provide
> some
> > basic functions called by compiler:
> >
> >
> https://github.com/gcc-mirror/gcc/tree/master/libstdc%2B%2B-v3/libsupc%2B%2B
> >
> > libsupc++ provides, however the Kconfig option
> > > `[ ] Have libsupc++ (required)`
> > > says, it's required.
> > >
> > > What's the right answer here? What are others doing about this?
> > >
> > >
> > Three methods you can try:
> >
> > 1. Switch to the ARM maintained toolchain
> > 2. Build libsupc++.a for NuttX toolchain
> > 3. Enhance NuttX's libc++ runtime support
> >
> >
> > https://github.com/apache/incubator-nuttx/tree/master/libs/libxx
> >
> >
> > > Is getting NuttX buildroot to build and provide libsupc++.a the *right*
> > > solution?
> > >
> > >
> > Yes, a complete toolchain should provide libsupc++.a. libsupc++.a just
> like
> > libgcc.a should part of toolchain, not part of c/c++ library
> > implemetnation, because libsupc++.a tightly couple with the implementaion
> > detail of compiler.
> >
> >
> > > Do we need to change how libcxx is built in this case?
> > >
> > >
> >
> https://libcxx.llvm.org/docs/BuildingLibcxx.html#using-alternate-abi-libraries
> > >
> > >
> > Then you need port the libcxxrt:
> > https://github.com/libcxxrt/libcxxrt
> >
> >
> > > Thank you!
> > >
> > > Anthony
> > >
> >
>
Re: libcxx and buildroot toolchain
Posted by Anthony Merlino <an...@vergeaero.com>.
Thanks for the info Xiang! I was on the right track but it is good to have
some affirmation that I'm not missing something.
The issue with the Arm maintained toolchain, as Greg has warned many times,
is its use of newlib. Are you doing anything to ensure the wrong math
library is not used?
I will work on improving buildroot to also build and include libsupcxx.a.
With Alan's modified version of libcxx, he disabled some exception logic
and maybe some other logic that was allowing me to build without libsupxx.a
entirely.
Also, may I ask why we are building libcxx by manually grabbing the source
files and building it? Are we against just driving the build from their
existing build system? I ask because there are options in the way libcxx is
built that might be useful to us and we have to replicate all of that if we
just grab the source.
Best,
Anthony
On Sat, Jan 9, 2021, 7:32 AM Xiang Xiao <xi...@gmail.com> wrote:
> On Fri, Jan 8, 2021 at 9:57 AM Anthony Merlino <an...@vergeaero.com>
> wrote:
>
> > Hey all,
> >
> > Would someone be willing to share their experience with libcxx and their
> > toolchain?
>
>
> This toolchain should work:
>
> https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-rm
>
>
> > I've now caught up to the tip of master, which now downloads
> > and builds libcxx for me instead of using Alan's modified version. I am
> > facing an issue I've faced before, and would really love to properly
> > understand how this is supposed to work.
> >
> > My issues mostly center around libsupc++.a
> >
> > Currently, my build fails because it can't find libsupc++. From my
> > understanding, this should be provided by my toolchain. But I am using a
> > toolchain built by the NuttX buildroot and it does not build the C++
> > libraries. I am not using RTTI or exceptions, so I don't need what
> >
>
> libsupc++.a doesn't only provide RTTI and exectpions, but also provide some
> basic functions called by compiler:
>
> https://github.com/gcc-mirror/gcc/tree/master/libstdc%2B%2B-v3/libsupc%2B%2B
>
> libsupc++ provides, however the Kconfig option
> > `[ ] Have libsupc++ (required)`
> > says, it's required.
> >
> > What's the right answer here? What are others doing about this?
> >
> >
> Three methods you can try:
>
> 1. Switch to the ARM maintained toolchain
> 2. Build libsupc++.a for NuttX toolchain
> 3. Enhance NuttX's libc++ runtime support
>
>
> https://github.com/apache/incubator-nuttx/tree/master/libs/libxx
>
>
> > Is getting NuttX buildroot to build and provide libsupc++.a the *right*
> > solution?
> >
> >
> Yes, a complete toolchain should provide libsupc++.a. libsupc++.a just like
> libgcc.a should part of toolchain, not part of c/c++ library
> implemetnation, because libsupc++.a tightly couple with the implementaion
> detail of compiler.
>
>
> > Do we need to change how libcxx is built in this case?
> >
> >
> https://libcxx.llvm.org/docs/BuildingLibcxx.html#using-alternate-abi-libraries
> >
> >
> Then you need port the libcxxrt:
> https://github.com/libcxxrt/libcxxrt
>
>
> > Thank you!
> >
> > Anthony
> >
>
Re: libcxx and buildroot toolchain
Posted by Xiang Xiao <xi...@gmail.com>.
On Fri, Jan 8, 2021 at 9:57 AM Anthony Merlino <an...@vergeaero.com>
wrote:
> Hey all,
>
> Would someone be willing to share their experience with libcxx and their
> toolchain?
This toolchain should work:
https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-rm
> I've now caught up to the tip of master, which now downloads
> and builds libcxx for me instead of using Alan's modified version. I am
> facing an issue I've faced before, and would really love to properly
> understand how this is supposed to work.
>
> My issues mostly center around libsupc++.a
>
> Currently, my build fails because it can't find libsupc++. From my
> understanding, this should be provided by my toolchain. But I am using a
> toolchain built by the NuttX buildroot and it does not build the C++
> libraries. I am not using RTTI or exceptions, so I don't need what
>
libsupc++.a doesn't only provide RTTI and exectpions, but also provide some
basic functions called by compiler:
https://github.com/gcc-mirror/gcc/tree/master/libstdc%2B%2B-v3/libsupc%2B%2B
libsupc++ provides, however the Kconfig option
> `[ ] Have libsupc++ (required)`
> says, it's required.
>
> What's the right answer here? What are others doing about this?
>
>
Three methods you can try:
1. Switch to the ARM maintained toolchain
2. Build libsupc++.a for NuttX toolchain
3. Enhance NuttX's libc++ runtime support
https://github.com/apache/incubator-nuttx/tree/master/libs/libxx
> Is getting NuttX buildroot to build and provide libsupc++.a the *right*
> solution?
>
>
Yes, a complete toolchain should provide libsupc++.a. libsupc++.a just like
libgcc.a should part of toolchain, not part of c/c++ library
implemetnation, because libsupc++.a tightly couple with the implementaion
detail of compiler.
> Do we need to change how libcxx is built in this case?
>
> https://libcxx.llvm.org/docs/BuildingLibcxx.html#using-alternate-abi-libraries
>
>
Then you need port the libcxxrt:
https://github.com/libcxxrt/libcxxrt
> Thank you!
>
> Anthony
>