libstdc++ is missing `gdb` pretty-printer integration about ctng-compilers-feedstock HOT 6 OPEN

The file is included wrongly as $PREFIX/lib/*-gdb.py. Can you figure out the reason and send a PR to fix it?

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I am somewhat new to conda, so I have three questions to investigate this further

1. I ran build-locally.py successfully. How do I now install the newly built packages, to see where they are placed?
2. Do we need to check whether we're cross-compiling? The commented out

# Probably don't want to do this for cross-compilers
# mkdir -p ${PREFIX}/share/gdb/auto-load/usr/lib/
# cp ${SRC_DIR}/gcc_built/${CHOST}/sysroot/lib/libstdc++.so.6.*-gdb.py ${PREFIX}/share/gdb/auto-load/usr/lib/

seems to suggest so, but it might need the target triplet x86_64-conda-linux-gnu as a prefix, to match the location of libstdc++.so
3. It seems like the standard library .so is provided by multiple packages:

./libstdcxx-ng-9.5.0-hf86b28c_16/lib/libstdc++.so.6.0.28
./gxx_impl_linux-64-9.5.0-h6c5bc03_16/lib/libstdc++.so.6.0.28-gdb.py
./gcc_bootstrap_linux-64-9.5.0-hf039093_10/lib/libstdc++.so.6.0.28-gdb.py
./gcc_bootstrap_linux-64-9.5.0-hf039093_10/x86_64-conda-linux-gnu/lib/libstdc++.so.6.0.28
./gcc_impl_linux-64-9.5.0-h6c5bc03_16/x86_64-conda-linux-gnu/lib/libstdc++.so.6.0.28

is libstdcxx-ng even necessary in that case? I'd assume that gxx_impl will be the one that is used in the end?

I can already tell you that the relevant line is make -C $CHOST/libstdc++-v3/python prefix=${PREFIX} install in install-g++.sh, but didn't dig further. If gcc used the library from libstdcxx-ng, at least the relative path would be correct, but if it used the one from gxx_impl, it would be missing the x86_64-conda-linux-gnu/ prefix.

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It seems like gxx_impl_linux-64 9.5.0 should work fine. Can you try updating gxx_impl_linux-64 in your env?

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Not sure what you're saying - I built gxx_impl_linux-64 9.5.0, and it contains the correct file, but in the wrong location. I'll see if I can fix it. In general, putting the file into auto-load regardless of whether we're cross-compiling or not seems safe, since the (not binary, but structural) layout of the types is pretty much architecture-independent.

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@upsj Were you able to make any more progress on this? This issue has been bugging me for a while now. Your write up helped me understand what was going on but I haven't been able to figure out a good workaround for this.

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@isuruf can you please explain why this code is commented out?

Without the *-gdb.py in the right place you don't get pretty-printing for libstdc++ symbols in debuggers. I see there is a file under $CONDA_PREFIX/lib/-gdb.py and I'm not sure how it gets there.

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