Compiler warnings from capnproto when building via add_subdirectory #138

Originally posted by @Sjors in https://github.com/bitcoin/bitcoin/pull/31741#pullrequestreview-2577588200

On (M4) macOS 15.2 I get a flood of warnings, which means I can't use -DWERROR=ON:

In file included from /opt/homebrew/include/capnp/common.h:31:
/opt/homebrew/include/kj/windows-sanity.h:39:6: warning: '_WIN32' is not defined, evaluates to 0 [-Wundef]
   39 | #if !_WIN32 && !__CYGWIN__
      |      ^
/opt/homebrew/include/kj/windows-sanity.h:39:17: warning: '__CYGWIN__' is not defined, evaluates to 0 [-Wundef]
   39 | #if !_WIN32 && !__CYGWIN__
      |     

/opt/homebrew/include/capnp/common.h:33:5: warning: 'CAPNP_DEBUG_TYPES' is not defined, evaluates to 0 [-Wundef]

/opt/homebrew/include/capnp/raw-schema.h:26:5: warning: '_MSC_VER' is not defined, evaluates to 0 [-Wundef]

/opt/homebrew/include/kj/async-prelude.h:34:6: warning: 'KJ_NO_EXCEPTIONS' is not defined, evaluates to 0 [-Wundef]

Using https://github.com/bitcoin/bitcoin/pull/31741 (https://github.com/ryanofsky/bitcoin/commits/pr/subtree.3) I don't see any warnings on my sstem, so help to provide more steps to reproduce.

If you can try building with make -C build VERBOSE=1 ... that would also help show the compiler comment lines so we can see if there's something wrong with -I -isystem -Wno-system-headers options that are being passed might be causing this issue.

On 93ba80b3d78fa1c4e7f614df6517b9cb492d05d7 (build directory deleted)

macOS 15.2 with Xcode 16.2

cmake -B build -DWERROR=OFF -DBUILD_MULTIPROCESS=ON

<details> <summary>log</summary>

-- The CXX compiler identification is AppleClang 16.0.0.16000026
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found SQLite3: /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.2.sdk/usr/include (found suitable version "3.43.2", minimum required is "3.7.17")
-- Performing Test CXX_SUPPORTS__WERROR
-- Performing Test CXX_SUPPORTS__WERROR - Success
-- Setting build type to "RelWithDebInfo" as none was specified
-- Performing Test CXX_SUPPORTS__G3
-- Performing Test CXX_SUPPORTS__G3 - Success
-- Performing Test LINKER_SUPPORTS__G3
-- Performing Test LINKER_SUPPORTS__G3 - Success
-- Performing Test CXX_SUPPORTS__FTRAPV
-- Performing Test CXX_SUPPORTS__FTRAPV - Success
-- Performing Test LINKER_SUPPORTS__FTRAPV
-- Performing Test LINKER_SUPPORTS__FTRAPV - Success
-- Performing Test LINKER_SUPPORTS__WL__FATAL_WARNINGS
-- Performing Test LINKER_SUPPORTS__WL__FATAL_WARNINGS - Success
-- Performing Test LINKER_SUPPORTS__WL__DEAD_STRIP
-- Performing Test LINKER_SUPPORTS__WL__DEAD_STRIP - Success
-- Performing Test LINKER_SUPPORTS__WL__DEAD_STRIP_DYLIBS
-- Performing Test LINKER_SUPPORTS__WL__DEAD_STRIP_DYLIBS - Success
-- Performing Test LINKER_SUPPORTS__WL__HEADERPAD_MAX_INSTALL_NAMES
-- Performing Test LINKER_SUPPORTS__WL__HEADERPAD_MAX_INSTALL_NAMES - Success
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD - Success
-- Found Threads: TRUE
-- Found Boost: /opt/homebrew/include (found suitable version "1.87.0", minimum required is "1.73.0")
-- Performing Test NO_DIAGNOSTICS_BOOST_NO_CXX98_FUNCTION_BASE
-- Performing Test NO_DIAGNOSTICS_BOOST_NO_CXX98_FUNCTION_BASE - Failed
-- Found PkgConfig: /opt/homebrew/bin/pkg-config (found version "2.3.0")
-- Found Libevent: /opt/homebrew/Cellar/libevent/2.1.12_1/lib (found suitable version "2.1.12-stable", minimum required is "2.1.8")
-- Performing Test HAVE_EVHTTP_CONNECTION_GET_PEER_CONST_CHAR
-- Performing Test HAVE_EVHTTP_CONNECTION_GET_PEER_CONST_CHAR - Failed
-- Looking for C++ include sys/prctl.h
-- Looking for C++ include sys/prctl.h - not found
-- Looking for C++ include sys/resources.h
-- Looking for C++ include sys/resources.h - not found
-- Looking for C++ include sys/vmmeter.h
-- Looking for C++ include sys/vmmeter.h - found
-- Looking for C++ include vm/vm_param.h
-- Looking for C++ include vm/vm_param.h - not found
-- Looking for O_CLOEXEC
-- Looking for O_CLOEXEC - found
-- Looking for fdatasync
-- Looking for fdatasync - not found
-- Looking for fork
-- Looking for fork - found
-- Looking for pipe2
-- Looking for pipe2 - not found
-- Looking for setsid
-- Looking for setsid - found
-- Looking for C++ include sys/types.h
-- Looking for C++ include sys/types.h - found
-- Looking for C++ include ifaddrs.h
-- Looking for C++ include ifaddrs.h - found
-- Performing Test IFADDR_LINKS_WITHOUT_LIBSOCKET
-- Performing Test IFADDR_LINKS_WITHOUT_LIBSOCKET - Success
-- Performing Test STD_ATOMIC_LINKS_WITHOUT_LIBATOMIC
-- Performing Test STD_ATOMIC_LINKS_WITHOUT_LIBATOMIC - Success
-- Looking for std::system
-- Looking for std::system - found
-- Looking for ::_wsystem
-- Looking for ::_wsystem - not found
-- Performing Test STRERROR_R_CHAR_P
-- Performing Test STRERROR_R_CHAR_P - Failed
-- Looking for malloc_info
-- Looking for malloc_info - not found
-- Performing Test HAVE_MALLOPT_ARENA_MAX
-- Performing Test HAVE_MALLOPT_ARENA_MAX - Failed
-- Performing Test HAVE_POSIX_FALLOCATE
-- Performing Test HAVE_POSIX_FALLOCATE - Failed
-- Performing Test HAVE_STRONG_GETAUXVAL
-- Performing Test HAVE_STRONG_GETAUXVAL - Failed
-- Performing Test HAVE_SOCKADDR_UN
-- Performing Test HAVE_SOCKADDR_UN - Success
-- Performing Test HAVE_GETRANDOM
-- Performing Test HAVE_GETRANDOM - Failed
-- Performing Test HAVE_GETENTROPY_RAND
-- Performing Test HAVE_GETENTROPY_RAND - Success
-- Performing Test HAVE_SYSCTL
-- Performing Test HAVE_SYSCTL - Success
-- Performing Test HAVE_SYSCTL_ARND
-- Performing Test HAVE_SYSCTL_ARND - Failed
-- Performing Test HAVE_SSE41
-- Performing Test HAVE_SSE41 - Failed
-- Performing Test HAVE_AVX2
-- Performing Test HAVE_AVX2 - Failed
-- Performing Test HAVE_X86_SHANI
-- Performing Test HAVE_X86_SHANI - Failed
-- Performing Test HAVE_ARM_SHANI
-- Performing Test HAVE_ARM_SHANI - Success
-- Performing Test CXX_SUPPORTS__WALL
-- Performing Test CXX_SUPPORTS__WALL - Success
-- Performing Test CXX_SUPPORTS__WEXTRA
-- Performing Test CXX_SUPPORTS__WEXTRA - Success
-- Performing Test CXX_SUPPORTS__WGNU
-- Performing Test CXX_SUPPORTS__WGNU - Success
-- Performing Test CXX_SUPPORTS__WFORMAT__WFORMAT_SECURITY
-- Performing Test CXX_SUPPORTS__WFORMAT__WFORMAT_SECURITY - Success
-- Performing Test CXX_SUPPORTS__WVLA
-- Performing Test CXX_SUPPORTS__WVLA - Success
-- Performing Test CXX_SUPPORTS__WSHADOW_FIELD
-- Performing Test CXX_SUPPORTS__WSHADOW_FIELD - Success
-- Performing Test CXX_SUPPORTS__WTHREAD_SAFETY
-- Performing Test CXX_SUPPORTS__WTHREAD_SAFETY - Success
-- Performing Test CXX_SUPPORTS__WLOOP_ANALYSIS
-- Performing Test CXX_SUPPORTS__WLOOP_ANALYSIS - Success
-- Performing Test CXX_SUPPORTS__WREDUNDANT_DECLS
-- Performing Test CXX_SUPPORTS__WREDUNDANT_DECLS - Success
-- Performing Test CXX_SUPPORTS__WUNUSED_MEMBER_FUNCTION
-- Performing Test CXX_SUPPORTS__WUNUSED_MEMBER_FUNCTION - Success
-- Performing Test CXX_SUPPORTS__WDATE_TIME
-- Performing Test CXX_SUPPORTS__WDATE_TIME - Success
-- Performing Test CXX_SUPPORTS__WCONDITIONAL_UNINITIALIZED
-- Performing Test CXX_SUPPORTS__WCONDITIONAL_UNINITIALIZED - Success
-- Performing Test CXX_SUPPORTS__WDUPLICATED_BRANCHES
-- Performing Test CXX_SUPPORTS__WDUPLICATED_BRANCHES - Failed
-- Performing Test CXX_SUPPORTS__WDUPLICATED_COND
-- Performing Test CXX_SUPPORTS__WDUPLICATED_COND - Failed
-- Performing Test CXX_SUPPORTS__WLOGICAL_OP
-- Performing Test CXX_SUPPORTS__WLOGICAL_OP - Failed
-- Performing Test CXX_SUPPORTS__WOVERLOADED_VIRTUAL
-- Performing Test CXX_SUPPORTS__WOVERLOADED_VIRTUAL - Success
-- Performing Test CXX_SUPPORTS__WSUGGEST_OVERRIDE
-- Performing Test CXX_SUPPORTS__WSUGGEST_OVERRIDE - Success
-- Performing Test CXX_SUPPORTS__WIMPLICIT_FALLTHROUGH
-- Performing Test CXX_SUPPORTS__WIMPLICIT_FALLTHROUGH - Success
-- Performing Test CXX_SUPPORTS__WUNREACHABLE_CODE
-- Performing Test CXX_SUPPORTS__WUNREACHABLE_CODE - Success
-- Performing Test CXX_SUPPORTS__WDOCUMENTATION
-- Performing Test CXX_SUPPORTS__WDOCUMENTATION - Success
-- Performing Test CXX_SUPPORTS__WSELF_ASSIGN
-- Performing Test CXX_SUPPORTS__WSELF_ASSIGN - Success
-- Performing Test CXX_SUPPORTS__WBIDI_CHARS_ANY
-- Performing Test CXX_SUPPORTS__WBIDI_CHARS_ANY - Failed
-- Performing Test CXX_SUPPORTS__WUNDEF
-- Performing Test CXX_SUPPORTS__WUNDEF - Success
-- Performing Test CXX_SUPPORTS__WUNUSED_PARAMETER
-- Performing Test CXX_SUPPORTS__WUNUSED_PARAMETER - Success
-- Performing Test CXX_SUPPORTS__FNO_EXTENDED_IDENTIFIERS
-- Performing Test CXX_SUPPORTS__FNO_EXTENDED_IDENTIFIERS - Failed
-- Performing Test CXX_SUPPORTS__FDEBUG_PREFIX_MAP_A_B
-- Performing Test CXX_SUPPORTS__FDEBUG_PREFIX_MAP_A_B - Success
-- Performing Test CXX_SUPPORTS__FMACRO_PREFIX_MAP_A_B
-- Performing Test CXX_SUPPORTS__FMACRO_PREFIX_MAP_A_B - Success
-- Performing Test CXX_SUPPORTS__FSTACK_REUSE_NONE
-- Performing Test CXX_SUPPORTS__FSTACK_REUSE_NONE - Failed
-- Performing Test CXX_SUPPORTS__U_FORTIFY_SOURCE__D_FORTIFY_SOURCE_3_cc10
-- Performing Test CXX_SUPPORTS__U_FORTIFY_SOURCE__D_FORTIFY_SOURCE_3_cc10 - Success
-- Performing Test LINKER_SUPPORTS__U_FORTIFY_SOURCE__D_FORTIFY_SOURCE_3_cc10
-- Performing Test LINKER_SUPPORTS__U_FORTIFY_SOURCE__D_FORTIFY_SOURCE_3_cc10 - Success
-- Performing Test CXX_SUPPORTS__WSTACK_PROTECTOR
-- Performing Test CXX_SUPPORTS__WSTACK_PROTECTOR - Success
-- Performing Test CXX_SUPPORTS__FSTACK_PROTECTOR_ALL
-- Performing Test CXX_SUPPORTS__FSTACK_PROTECTOR_ALL - Success
-- Performing Test LINKER_SUPPORTS__FSTACK_PROTECTOR_ALL
-- Performing Test LINKER_SUPPORTS__FSTACK_PROTECTOR_ALL - Success
-- Performing Test CXX_SUPPORTS__FCF_PROTECTION_FULL
-- Performing Test CXX_SUPPORTS__FCF_PROTECTION_FULL - Failed
-- Performing Test CXX_SUPPORTS__FSTACK_CLASH_PROTECTION
-- Performing Test CXX_SUPPORTS__FSTACK_CLASH_PROTECTION - Failed
-- Performing Test CXX_SUPPORTS__MBRANCH_PROTECTION_BTI
-- Performing Test CXX_SUPPORTS__MBRANCH_PROTECTION_BTI - Success
-- Performing Test LINKER_SUPPORTS__WL___ENABLE_RELOC_SECTION
-- Performing Test LINKER_SUPPORTS__WL___ENABLE_RELOC_SECTION - Failed
-- Performing Test LINKER_SUPPORTS__WL___DYNAMICBASE
-- Performing Test LINKER_SUPPORTS__WL___DYNAMICBASE - Failed
-- Performing Test LINKER_SUPPORTS__WL___NXCOMPAT
-- Performing Test LINKER_SUPPORTS__WL___NXCOMPAT - Failed
-- Performing Test LINKER_SUPPORTS__WL___HIGH_ENTROPY_VA
-- Performing Test LINKER_SUPPORTS__WL___HIGH_ENTROPY_VA - Failed
-- Performing Test LINKER_SUPPORTS__WL__Z_RELRO
-- Performing Test LINKER_SUPPORTS__WL__Z_RELRO - Failed
-- Performing Test LINKER_SUPPORTS__WL__Z_NOW
-- Performing Test LINKER_SUPPORTS__WL__Z_NOW - Failed
-- Performing Test LINKER_SUPPORTS__WL__Z_SEPARATE_CODE
-- Performing Test LINKER_SUPPORTS__WL__Z_SEPARATE_CODE - Failed
-- Performing Test LINKER_SUPPORTS__WL__FIXUP_CHAINS
-- Performing Test LINKER_SUPPORTS__WL__FIXUP_CHAINS - Success
-- Found Python3: /opt/homebrew/Frameworks/Python.framework/Versions/3.13/bin/python3.13 (found suitable version "3.13.1", minimum required is "3.10") found components: Interpreter
-- Found Doxygen: /opt/homebrew/bin/doxygen (found version "1.13.2") found components: doxygen dot
-- Performing Test HAVE_BUILTIN_PREFETCH
-- Performing Test HAVE_BUILTIN_PREFETCH - Success
-- Performing Test HAVE_MM_PREFETCH
-- Performing Test HAVE_MM_PREFETCH - Failed
-- Performing Test HAVE_SSE42
-- Performing Test HAVE_SSE42 - Failed
-- Performing Test HAVE_ARM64_CRC32C
-- Performing Test HAVE_ARM64_CRC32C - Success
-- Looking for F_FULLFSYNC
-- Looking for F_FULLFSYNC - found
-- Performing Test HAVE_CLMUL
-- Performing Test HAVE_CLMUL - Failed
CMake Deprecation Warning at src/ipc/libmultiprocess/CMakeLists.txt:5 (cmake_minimum_required):
  Compatibility with CMake < 3.10 will be removed from a future version of
  CMake.

  Update the VERSION argument <min> value.  Or, use the <min>...<max> syntax
  to tell CMake that the project requires at least <min> but has been updated
  to work with policies introduced by <max> or earlier.


-- Found ZLIB: /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.2.sdk/usr/lib/libz.tbd (found version "1.2.12")
-- Performing Test HAVE_PTHREAD_GETNAME_NP
-- Performing Test HAVE_PTHREAD_GETNAME_NP - Success
-- Performing Test HAVE_PTHREAD_THREADID_NP
-- Performing Test HAVE_PTHREAD_THREADID_NP - Success
-- Performing Test HAVE_PTHREAD_GETTHREADID_NP
-- Performing Test HAVE_PTHREAD_GETTHREADID_NP - Failed

Configuring secp256k1 subtree...
-- The C compiler identification is AppleClang 16.0.0.16000026
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Performing Test HAVE_X86_64_ASM
-- Performing Test HAVE_X86_64_ASM - Failed
-- Could NOT find Valgrind (missing: Valgrind_INCLUDE_DIR Valgrind_WORKS) 
-- Performing Test C_SUPPORTS__PEDANTIC
-- Performing Test C_SUPPORTS__PEDANTIC - Success
-- Performing Test C_SUPPORTS__WALL
-- Performing Test C_SUPPORTS__WALL - Success
-- Performing Test C_SUPPORTS__WCAST_ALIGN
-- Performing Test C_SUPPORTS__WCAST_ALIGN - Success
-- Performing Test C_SUPPORTS__WCAST_ALIGN_STRICT
-- Performing Test C_SUPPORTS__WCAST_ALIGN_STRICT - Failed
-- Performing Test C_SUPPORTS__WCONDITIONAL_UNINITIALIZED
-- Performing Test C_SUPPORTS__WCONDITIONAL_UNINITIALIZED - Success
-- Performing Test C_SUPPORTS__WEXTRA
-- Performing Test C_SUPPORTS__WEXTRA - Success
-- Performing Test C_SUPPORTS__WNESTED_EXTERNS
-- Performing Test C_SUPPORTS__WNESTED_EXTERNS - Success
-- Performing Test C_SUPPORTS__WNO_LONG_LONG
-- Performing Test C_SUPPORTS__WNO_LONG_LONG - Success
-- Performing Test C_SUPPORTS__WNO_OVERLENGTH_STRINGS
-- Performing Test C_SUPPORTS__WNO_OVERLENGTH_STRINGS - Success
-- Performing Test C_SUPPORTS__WNO_UNUSED_FUNCTION
-- Performing Test C_SUPPORTS__WNO_UNUSED_FUNCTION - Success
-- Performing Test C_SUPPORTS__WRESERVED_IDENTIFIER
-- Performing Test C_SUPPORTS__WRESERVED_IDENTIFIER - Success
-- Performing Test C_SUPPORTS__WSHADOW
-- Performing Test C_SUPPORTS__WSHADOW - Success
-- Performing Test C_SUPPORTS__WSTRICT_PROTOTYPES
-- Performing Test C_SUPPORTS__WSTRICT_PROTOTYPES - Success
-- Performing Test C_SUPPORTS__WUNDEF
-- Performing Test C_SUPPORTS__WUNDEF - Success


secp256k1 configure summary
===========================
Build artifacts:
  library type ........................ Static
Optional modules:
  ECDH ................................ OFF
  ECDSA pubkey recovery ............... ON
  extrakeys ........................... ON
  schnorrsig .......................... ON
  musig ............................... OFF
  ElligatorSwift ...................... ON
Parameters:
  ecmult window size .................. 15
  ecmult gen table size ............... 86 KiB
Optional features:
  assembly ............................ OFF
  external callbacks .................. OFF
Optional binaries:
  benchmark ........................... OFF
  noverify_tests ...................... ON
  tests ............................... ON
  exhaustive tests .................... ON
  ctime_tests ......................... OFF
  examples ............................ OFF

Cross compiling ....................... FALSE
Valgrind .............................. OFF
Preprocessor defined macros ........... ENABLE_MODULE_ELLSWIFT=1 ENABLE_MODULE_SCHNORRSIG=1 ENABLE_MODULE_EXTRAKEYS=1 ENABLE_MODULE_RECOVERY=1 ECMULT_WINDOW_SIZE=15 COMB_BLOCKS=43 COMB_TEETH=6
C compiler ............................ AppleClang 16.0.0.16000026, /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc
CFLAGS ................................ 
Compile options ....................... -pedantic -Wall -Wcast-align -Wconditional-uninitialized -Wextra -Wnested-externs -Wno-long-long -Wno-overlength-strings -Wno-unused-function -Wreserved-identifier -Wshadow -Wstrict-prototypes -Wundef
Build type:
 - CMAKE_BUILD_TYPE ................... RelWithDebInfo
 - CFLAGS ............................. -O2 -g 
 - LDFLAGS for executables ............ 
 - LDFLAGS for shared libraries ....... 



Configure summary
=================
Executables:
  bitcoind ............................ ON
  bitcoin-node (multiprocess) ......... ON
  bitcoin-qt (GUI) .................... OFF
  bitcoin-gui (GUI, multiprocess) ..... OFF
  bitcoin-cli ......................... ON
  bitcoin-tx .......................... ON
  bitcoin-util ........................ ON
  bitcoin-wallet ...................... ON
  bitcoin-chainstate (experimental) ... OFF
  libbitcoinkernel (experimental) ..... OFF
Optional features:
  wallet support ...................... ON
   - descriptor wallets (SQLite) ...... ON
   - legacy wallets (Berkeley DB) ..... OFF
  external signer ..................... ON
  ZeroMQ .............................. OFF
  USDT tracing ........................ OFF
  QR code (GUI) ....................... OFF
  DBus (GUI, Linux only) .............. OFF
Tests:
  test_bitcoin ........................ ON
  test_bitcoin-qt ..................... OFF
  bench_bitcoin ....................... OFF
  fuzz binary ......................... OFF

Cross compiling ....................... FALSE
C++ compiler .......................... AppleClang 16.0.0.16000026, /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++
CMAKE_BUILD_TYPE ...................... RelWithDebInfo
Preprocessor defined macros ........... OBJC_OLD_DISPATCH_PROTOTYPES=0
C++ compiler flags .................... -O2 -g -std=c++20 -fPIC -fdebug-prefix-map=/Users/sjors/dev/bitcoin/src=. -fmacro-prefix-map=/Users/sjors/dev/bitcoin/src=. -Wall -Wextra -Wgnu -Wformat -Wformat-security -Wvla -Wshadow-field -Wthread-safety -Wloop-analysis -Wredundant-decls -Wunused-member-function -Wdate-time -Wconditional-uninitialized -Woverloaded-virtual -Wsuggest-override -Wimplicit-fallthrough -Wunreachable-code -Wdocumentation -Wself-assign -Wundef -Wno-unused-parameter -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=3 -Wstack-protector -fstack-protector-all -mbranch-protection=bti
Linker flags .......................... -O2 -g -Wl,-dead_strip -Wl,-dead_strip_dylibs -Wl,-headerpad_max_install_names -fstack-protector-all -Wl,-fixup_chains -fPIE -Xlinker -pie

NOTE: The summary above may not exactly match the final applied build flags
      if any additional CMAKE_* or environment variables have been modified.
      To see the exact flags applied, build with the --verbose option.

Attempt to harden executables ......... ON
Treat compiler warnings as errors ..... OFF
Use ccache for compiling .............. ON


-- Configuring done (8.9s)
-- Generating done (0.2s)
-- Build files have been written to: /Users/sjors/dev/bitcoin/build

</details>

cmake --build build -j 15 --verbose

That's so verbose it doesn't fit in a comment :-)

https://gist.githubusercontent.com/Sjors/2307c73a2db59ca802f5c32d73d175d1/raw/52766be20a47be34447e9bfb87e86d5780e541ed/gistfile1.txt

Happens on CI too: https://github.com/bitcoin/bitcoin/actions/runs/13037449380/job/36371318715?pr=30975

@hebasto do you have any ideas on how to fix these warning: 'XXXXX' is not defined, evaluates to 0 [-Wundef] errors?

I know in the old build system we had a SUPPRESS_WARNINGS workaround for this that used -isystem instead of -I to avoid them: 79e197b from https://github.com/bitcoin/bitcoin/pull/29876

But I can't find an equivalent workaround in the cmake build. I would expect -Wundef problem didn't disappear so we much be working around it somehow?

Shouldn't these be wrapped in defined(...)?

Shouldn't these be wrapped in defined(...)?

These warnings are coming from capnproto. I think in most projects using #if UNDEFINED_SYMBOL is very common and using -Wundef is more rare, and in general we shouldn't be enforcing warnings in external headers.

Not to mention that if defined(SYMBOL) can cause problems because -DSYMBOL=0 will not work.

I feel like I'm pretty stuck here. I've been trying to make a similar failure happen on my system, but not getting anywhere. I think maybe following changes would be more correct and might get rid of the errors from boost and capnproto here, but this is a bit of a shot in the dark:

--- a/src/ipc/libmultiprocess/CMakeLists.txt
+++ b/src/ipc/libmultiprocess/CMakeLists.txt
@@ -93,10 +93,10 @@ target_include_directories(multiprocess PUBLIC
   $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
   $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
   ${CAPNP_INCLUDE_DIRECTORY})
-target_link_libraries(multiprocess PRIVATE CapnProto::capnp)
-target_link_libraries(multiprocess PRIVATE CapnProto::capnp-rpc)
-target_link_libraries(multiprocess PRIVATE CapnProto::kj)
-target_link_libraries(multiprocess PRIVATE CapnProto::kj-async)
+target_link_libraries(multiprocess PUBLIC CapnProto::capnp)
+target_link_libraries(multiprocess PUBLIC CapnProto::capnp-rpc)
+target_link_libraries(multiprocess PUBLIC CapnProto::kj)
+target_link_libraries(multiprocess PUBLIC CapnProto::kj-async)
 set_target_properties(multiprocess PROPERTIES
     PUBLIC_HEADER "${MP_PUBLIC_HEADERS}")
 install(TARGETS multiprocess EXPORT LibTargets
--- a/src/test/CMakeLists.txt
+++ b/src/test/CMakeLists.txt
@@ -164,6 +164,7 @@ endif()
 if(BUILD_MULTIPROCESS)
   target_link_libraries(bitcoin_ipc_test
     PRIVATE
+      Boost::headers
       core_interface
       univalue
   )

I'll give them a try, waiting for the Windows job on the last push: https://github.com/bitcoin/bitcoin/actions/runs/13054985470/job/36423710000?pr=30975

(actually there's no use in waiting for Windows with multiprocess)

The diff suggested in https://github.com/chaincodelabs/libmultiprocess/issues/138#issuecomment-2624919124 did seem to successfully fix the header warnings in the macos 14 native job here: https://github.com/bitcoin/bitcoin/pull/30975#issuecomment-2625235833