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Asio from Boost 1.86.0 fails to build with C++20 w/o concepts #1547

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iv-m opened this issue Oct 19, 2024 · 2 comments · May be fixed by #1556
Open

Asio from Boost 1.86.0 fails to build with C++20 w/o concepts #1547

iv-m opened this issue Oct 19, 2024 · 2 comments · May be fixed by #1556

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@iv-m
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iv-m commented Oct 19, 2024

When porting my software to boost 1.86.0, I found a strange error that I narrowed down to the following example.

test.cpp:

#include <boost/asio.hpp>

int main() { return 0; }
$ g++ -DBOOST_ASIO_DISABLE_CONCEPTS -std=c++20 test.cpp
In file included from /usr/include/boost/asio.hpp:69,
                 from test.cpp:2:
/usr/include/boost/asio/co_composed.hpp:849:13: error: ‘async_operation’ has not been declared
  849 |   template <async_operation Op>
      |             ^~~~~~~~~~~~~~~
/usr/include/boost/asio/co_composed.hpp:850:24: error: ‘Op’ has not been declared
  850 |   auto await_transform(Op&& op
      |                        ^~
[... and a few more errors, as compiler does not now what Op is]

I'm using x86_64 linux, gcc 13.2.1.

I see a similar error with clang 18.1.8.

If I drop -DBOOST_ASIO_DISABLE_CONCEPTS or standard specification, the code compiles just fine.
@FireBurn
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FireBurn commented Nov 4, 2024

I'm also seeing this in Clang 19.1.3

@iv-m
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iv-m commented Nov 5, 2024

Yeah, same with gcc 14.2.1 and calng 19.1.3.

Also I get a similar error for the current master from this repo (bb85475):

$ cat $TMPDIR/reproducer.cpp
#include <asio.hpp>

int main() { return 0; }
$ g++ -DASIO_DISABLE_CONCEPTS -Iasio/include  -std=c++20 "$TMPDIR/reproducer.cpp"
In file included from asio/include/asio.hpp:67,
                 from /tmp/.private/iv/reproducer.cpp:1:
asio/include/asio/co_composed.hpp:848:13: error: ‘async_operation’ has not been declared
  848 |   template <async_operation Op>
      |             ^~~~~~~~~~~~~~~
asio/include/asio/co_composed.hpp:849:24: error: ‘Op’ has not been declared
  849 |   auto await_transform(Op&& op
      |                        ^~

iv-m added a commit to iv-m/asio that referenced this issue Nov 5, 2024
@iv-m
co_composed.hpp: Guard use of async_operation
a8db5f3 
`async_operation` is defined only when concepts are in use.
When ASIO_DISABLE_CONCEPTS is defined, bare `typename`
should be used instead.

We can't use ASIO_ASYNC_OPERATION macros here, as it currently
does not have a no-argument form.

Fixes: chriskohlhoff#1547
@iv-m iv-m linked a pull request Nov 5, 2024 that will close this issue
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co_composed.hpp: Guard use of async_operation iv-m/asio
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@FireBurn @iv-m