net: Fix -Wmissing-braces

[hebasto]

On some non-POSIX platforms, Clang emits -Wmissing-braces warnings for the IN6ADDR_ANY_INIT and IN6ADDR_LOOPBACK_INIT macros. For example, on OpenIndiana / illumos:

$ uname -srv
SunOS 5.11 illumos-325e0fc8bb
$ clang --version
clang version 21.1.7 (https://github.com/OpenIndiana/oi-userland.git 36a81bf5e5d307d4e85893422600678d46328010)
Target: x86_64-pc-solaris2.11
Thread model: posix
InstalledDir: /usr/clang/21/bin
$ cmake -B build -DCMAKE_GENERATOR=Ninja -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DENABLE_IPC=OFF -DAPPEND_CXXFLAGS='-Wno-unused-command-line-argument'
$ cmake --build build
[284/573] Building CXX object src/CMakeFiles/bitcoin_node.dir/net.cpp.o
/export/home/hebasto/dev/bitcoin/src/net.cpp:3309:42: warning: suggest braces around initialization of subobject [-Wmissing-braces]
 3309 |         const CService ipv6_any{in6_addr(IN6ADDR_ANY_INIT), GetListenPort()}; // ::
      |                                          ^~~~~~~~~~~~~~~~
/usr/include/netinet/in.h:479:32: note: expanded from macro 'IN6ADDR_ANY_INIT'
  479 | #define IN6ADDR_ANY_INIT            {   0, 0, 0, 0,     \
      |                                         ^~~~~~~~~~~~~~~~~
  480 |                                         0, 0, 0, 0,     \
      |                                         ~~~~~~~~~~~~~~~~~
  481 |                                         0, 0, 0, 0,     \
      |                                         ~~~~~~~~~~~~~~~~~
  482 |                                         0, 0, 0, 0 }
      |                                         ~~~~~~~~~~
1 warning generated.
[467/573] Building CXX object src/test/CMakeFiles/test_bitcoin.dir/i2p_tests.cpp.o
/export/home/hebasto/dev/bitcoin/src/test/i2p_tests.cpp:116:34: warning: suggest braces around initialization of subobject [-Wmissing-braces]
  116 |     const CService addr{in6_addr(IN6ADDR_LOOPBACK_INIT), /*port=*/7656};
      |                                  ^~~~~~~~~~~~~~~~~~~~~
/usr/include/netinet/in.h:484:37: note: expanded from macro 'IN6ADDR_LOOPBACK_INIT'
  484 | #define IN6ADDR_LOOPBACK_INIT       {   0, 0, 0, 0,     \
      |                                         ^~~~~~~~~~~~~~~~~
  485 |                                         0, 0, 0, 0,     \
      |                                         ~~~~~~~~~~~~~~~~~
  486 |                                         0, 0, 0, 0,     \
      |                                         ~~~~~~~~~~~~~~~~~
  487 |                                         0, 0, 0, 0x1U }
      |                                         ~~~~~~~~~~~~~
/export/home/hebasto/dev/bitcoin/src/test/i2p_tests.cpp:159:38: warning: suggest braces around initialization of subobject [-Wmissing-braces]
  159 |         const CService addr{in6_addr(IN6ADDR_LOOPBACK_INIT), /*port=*/7656};
      |                                      ^~~~~~~~~~~~~~~~~~~~~
/usr/include/netinet/in.h:484:37: note: expanded from macro 'IN6ADDR_LOOPBACK_INIT'
  484 | #define IN6ADDR_LOOPBACK_INIT       {   0, 0, 0, 0,     \
      |                                         ^~~~~~~~~~~~~~~~~
  485 |                                         0, 0, 0, 0,     \
      |                                         ~~~~~~~~~~~~~~~~~
  486 |                                         0, 0, 0, 0,     \
      |                                         ~~~~~~~~~~~~~~~~~
  487 |                                         0, 0, 0, 0x1U }
      |                                         ~~~~~~~~~~~~~
2 warnings generated.
[483/573] Building CXX object src/test/CMakeFiles/test_bitcoin.dir/netbase_tests.cpp.o
/export/home/hebasto/dev/bitcoin/src/test/netbase_tests.cpp:505:36: warning: suggest braces around initialization of subobject [-Wmissing-braces]
  505 |         CService(CNetAddr(in6_addr(IN6ADDR_LOOPBACK_INIT)), 0 /* port */),
      |                                    ^~~~~~~~~~~~~~~~~~~~~
/usr/include/netinet/in.h:484:37: note: expanded from macro 'IN6ADDR_LOOPBACK_INIT'
  484 | #define IN6ADDR_LOOPBACK_INIT       {   0, 0, 0, 0,     \
      |                                         ^~~~~~~~~~~~~~~~~
  485 |                                         0, 0, 0, 0,     \
      |                                         ~~~~~~~~~~~~~~~~~
  486 |                                         0, 0, 0, 0,     \
      |                                         ~~~~~~~~~~~~~~~~~
  487 |                                         0, 0, 0, 0x1U }
      |                                         ~~~~~~~~~~~~~
/export/home/hebasto/dev/bitcoin/src/test/netbase_tests.cpp:510:36: warning: suggest braces around initialization of subobject [-Wmissing-braces]
  510 |         CService(CNetAddr(in6_addr(IN6ADDR_LOOPBACK_INIT)), 0x00f1 /* port */),
      |                                    ^~~~~~~~~~~~~~~~~~~~~
/usr/include/netinet/in.h:484:37: note: expanded from macro 'IN6ADDR_LOOPBACK_INIT'
  484 | #define IN6ADDR_LOOPBACK_INIT       {   0, 0, 0, 0,     \
      |                                         ^~~~~~~~~~~~~~~~~
  485 |                                         0, 0, 0, 0,     \
      |                                         ~~~~~~~~~~~~~~~~~
  486 |                                         0, 0, 0, 0,     \
      |                                         ~~~~~~~~~~~~~~~~~
  487 |                                         0, 0, 0, 0x1U }
      |                                         ~~~~~~~~~~~~~
/export/home/hebasto/dev/bitcoin/src/test/netbase_tests.cpp:515:36: warning: suggest braces around initialization of subobject [-Wmissing-braces]
  515 |         CService(CNetAddr(in6_addr(IN6ADDR_LOOPBACK_INIT)), 0xf1f2 /* port */),
      |                                    ^~~~~~~~~~~~~~~~~~~~~
/usr/include/netinet/in.h:484:37: note: expanded from macro 'IN6ADDR_LOOPBACK_INIT'
  484 | #define IN6ADDR_LOOPBACK_INIT       {   0, 0, 0, 0,     \
      |                                         ^~~~~~~~~~~~~~~~~
  485 |                                         0, 0, 0, 0,     \
      |                                         ~~~~~~~~~~~~~~~~~
  486 |                                         0, 0, 0, 0,     \
      |                                         ~~~~~~~~~~~~~~~~~
  487 |                                         0, 0, 0, 0x1U }
      |                                         ~~~~~~~~~~~~~
3 warnings generated.
[573/573] Linking CXX executable bin/test_bitcoin

The same issue is observed on Windows. For further details, see #31507.

[DrahtBot]

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Code Coverage & Benchmarks

For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/34090.

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Type	Reviewers
ACK	bensig, maflcko, vasild, sedited

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #31507 (build: Use clang-cl to build on Windows natively by hebasto)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

[fanquake]

https://github.com/bitcoin/bitcoin/actions/runs/20307057596/job/58327346295?pr=34090#step:11:495:

   net_processing.cpp
  netgroup.cpp
D:\a\bitcoin\bitcoin\src\net.cpp(3309,41): error C2440: '<function-style-cast>': cannot convert from 'initializer list' to 'in6_addr' [D:\a\bitcoin\bitcoin\build\src\bitcoin_node.vcxproj]
      D:\a\bitcoin\bitcoin\src\net.cpp(3309,41):
      'in6_addr::in6_addr': no overloaded function could convert all the argument types
          C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\shared\in6addr.h(30,1):
          could be 'in6_addr::in6_addr(in6_addr &&)'
              D:\a\bitcoin\bitcoin\src\net.cpp(3309,41):
              'in6_addr::in6_addr(in6_addr &&)': cannot convert argument 1 from 'initializer list' to 'in6_addr &&'
                  D:\a\bitcoin\bitcoin\src\net.cpp(3309,42):
                  Reason: cannot convert from 'initializer list' to 'in6_addr'
                  D:\a\bitcoin\bitcoin\src\net.cpp(3309,42):
                  Invalid aggregate initialization
                      D:\a\bitcoin\bitcoin\src\net.cpp(3309,42):
                      'initializing': cannot convert from 'initializer list' to 'UCHAR'
                          D:\a\bitcoin\bitcoin\src\net.cpp(3309,42):
                          Too many braces around initializer for 'UCHAR'
          C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\shared\in6addr.h(30,1):
          or       'in6_addr::in6_addr(const in6_addr &)'
              D:\a\bitcoin\bitcoin\src\net.cpp(3309,41):
              'in6_addr::in6_addr(const in6_addr &)': cannot convert argument 1 from 'initializer list' to 'const in6_addr &'
                  D:\a\bitcoin\bitcoin\src\net.cpp(3309,42):
                  Reason: cannot convert from 'initializer list' to 'const in6_addr'
                  D:\a\bitcoin\bitcoin\src\net.cpp(3309,42):
                  Invalid aggregate initialization
                      D:\a\bitcoin\bitcoin\src\net.cpp(3309,42):
                      'initializing': cannot convert from 'initializer list' to 'UCHAR'
                          D:\a\bitcoin\bitcoin\src\net.cpp(3309,42):
                          Too many braces around initializer for 'UCHAR'
          D:\a\bitcoin\bitcoin\src\net.cpp(3309,41):
          while trying to match the argument list '(initializer list)'

[hebasto]

https://github.com/bitcoin/bitcoin/actions/runs/20307057596/job/58327346295?pr=34090#step:11:495:

CI is green now.

[bensig]

ACK f46e3ec

Builds clean, netbase_tests and i2p_tests pass.
Clean fix using compat layer for platform-specific brace style in IN6ADDR_*_INIT macros.

[maflcko]

Would it not make sense to enable /we5246, and possibly have a CI output for /w15246 for reviewers? Otherwise, this may regress in the future before switching to clang?

[hebasto]

Would it not make sense to enable /we5246, and possibly have a CI output for /w15246 for reviewers?

MSVC has C5246 disabled by default for a reason. It emits tons of false positives: https://github.com/hebasto/bitcoin/actions/runs/21151989194/job/60829717946

Otherwise, this may regress in the future before switching to clang?

This can be handled by a new job in nightly builds.

[maflcko]

review ACK f46e3ec 👭

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[hebasto]

Friendly ping @vasild :)

[vasild]

ACK f46e3ec

Not tested.

[sedited]

utACK f46e3ec