dd-opentracing-cpp Win x64 - tracer.obj : error LNK2019: unresolved external symbol gethostname referenced in function "class datadog

[buzz3791]

When adding the following to my C++ application
#include <opentracing/dynamic_load.h>

I'm getting the following when linking against dd_opentracing.lib

tracer.obj : error LNK2019: unresolved external symbol gethostname referenced in function "class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __cdecl datadog::opentracing::`anonymous namespace'::reportingHostname(struct
datadog::opentracing::TracerOptions)" (?reportingHostname@?A0x5ef9dd98@opentracing@datadog@@YA?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@UTracerOptions@23@@Z) [C:\dev\ddog\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\.build\RelWithDebInfo\dd_opentracing.dll : fatal error LNK1120: 1 unresolved externals [C:\dev\ddog\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]

DETAILS:

C:\dev\ddog\dd-opentracing-cpp\.build>cmake .. "-DCMAKE_TOOLCHAIN_FILE=c:\dev\vcpkg\scripts\buildsystems\vcpkg.cmake"
-- Running vcpkg install
Detecting compiler hash for triplet x64-windows...
All requested packages are currently installed.
Total install time: 300 ns
curl provides CMake targets:

    # this is heuristically generated, and may not be correct
    find_package(CURL CONFIG REQUIRED)
    target_link_libraries(main PRIVATE CURL::libcurl)

msgpack provides CMake targets:

    # this is heuristically generated, and may not be correct
    find_package(msgpack-cxx CONFIG REQUIRED)
    target_link_libraries(main PRIVATE msgpack-cxx)

opentracing provides CMake targets:

    # this is heuristically generated, and may not be correct
    find_package(OpenTracing CONFIG REQUIRED)
    target_link_libraries(main PRIVATE OpenTracing::opentracing OpenTracing::opentracing_mocktracer)

-- Running vcpkg install - done
-- Selecting Windows SDK version 10.0.19041.0 to target Windows 10.0.18363.
-- find_package(CURL CONFIG REQUIRED)
--   using share/curl/vcpkg-cmake-wrapper.cmake
--   find_package(ZLIB 1 REQUIRED)
--     using share/zlib/vcpkg-cmake-wrapper.cmake
-- find_package(Threads REQUIRED)
-- find_package(Sanitizers )
--   find_package(ASan )
--   find_package(TSan )
--   find_package(MSan )
--   find_package(UBSan )
-- Compiler ID: MSVC
-- Configuring done (5.9s)
-- Generating done (0.1s)
-- Build files have been written to: C:/dev/ddog/dd-opentracing-cpp/.build

C:\dev\ddog\dd-opentracing-cpp\.build>cmake --build . -- -p:Configuration=RelWithDebInfo
MSBuild version 17.4.0+18d5aef85 for .NET Framework
  agent_writer.cpp
  bool.cpp
  dynamic_load.cpp
  encoder.cpp
  glob.cpp
  limiter.cpp
C:\dev\ddog\dd-opentracing-cpp\src\limiter.cpp(71,32): warning C4244: '+=': conversion from '_Rep' to 'long', possible loss of data [C:\dev\ddog\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
          with
          [
              _Rep=__int64
          ]
  logger.cpp
C:\dev\ddog\dd-opentracing-cpp\src\logger.cpp(23,21): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddog\dd-open
tracing-cpp\.build\dd_opentracing.vcxproj]
  opentracing_agent.cpp
  opentracing_external.cpp
  parse_util.cpp
  pending_trace.cpp
  sample.cpp
  sampling_mechanism.cpp
  sampling_priority.cpp
  span.cpp
C:\dev\ddog\dd-opentracing-cpp\src\span.cpp(214,45): warning C4101: 'ia': unreferenced local variable [C:\dev\ddog\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\span.cpp(216,41): warning C4101: 'oor': unreferenced local variable [C:\dev\ddog\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\span.cpp(389,43): warning C4101: 'ia': unreferenced local variable [C:\dev\ddog\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\span.cpp(392,39): warning C4101: 'oor': unreferenced local variable [C:\dev\ddog\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
  span_buffer.cpp
  span_context.cpp
  tag_propagation.cpp
  tags.cpp
  trace_data.cpp
  Generating Code...
  Compiling...
  tracer.cpp
C:\dev\ddog\dd-opentracing-cpp\src\tracer.cpp(66,23): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddog\dd-open
tracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer.cpp(94,27): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddog\dd-open
tracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer.cpp(102,27): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddog\dd-ope
ntracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer.cpp(117,38): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddog\dd-ope
ntracing-cpp\.build\dd_opentracing.vcxproj]
  tracer_factory.cpp
C:\dev\ddog\dd-opentracing-cpp\src\tracer_factory.cpp(8,19): warning C4273: '__p__environ': inconsistent dll linkage [C:\dev\ddog\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\Program Files (x86)\Windows Kits\10\Include\10.0.19041.0\ucrt\stdlib.h(1158,29): message : see previous definition of '__p__environ' [C:\dev\ddog\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
  tracer_options.cpp
C:\dev\ddog\dd-opentracing-cpp\src\tracer_options.cpp(131,39): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddo
g\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer_options.cpp(132,44): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddo
g\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer_options.cpp(198,27): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddo
g\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer_options.cpp(203,23): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddo
g\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer_options.cpp(208,23): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddo
g\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer_options.cpp(213,20): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddo
g\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer_options.cpp(230,26): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddo
g\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer_options.cpp(235,32): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddo
g\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer_options.cpp(246,30): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddo
g\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer_options.cpp(251,31): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddo
g\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer_options.cpp(256,23): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddo
g\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer_options.cpp(265,22): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddo
g\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer_options.cpp(274,31): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddo
g\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer_options.cpp(284,33): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddo
g\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer_options.cpp(299,30): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddo
g\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer_options.cpp(310,41): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddo
g\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer_options.cpp(321,27): warning C4996: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddo
g\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer_options.cpp(239,43): warning C4101: 'ia': unreferenced local variable [C:\dev\ddog\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer_options.cpp(241,39): warning C4101: 'oor': unreferenced local variable [C:\dev\ddog\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\src\tracer_options.cpp(341,30): warning C4996: 'localtime': This function or variable may be unsafe. Consider using localtime_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\de
v\ddog\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
  transport.cpp
C:\dev\ddog\dd-opentracing-cpp\src\transport.cpp(89,10): warning C4996: 'strncpy': This function or variable may be unsafe. Consider using strncpy_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. [C:\dev\ddog\dd-
opentracing-cpp\.build\dd_opentracing.vcxproj]
  version.cpp
  writer.cpp
  Generating Code...
     Creating library C:/dev/ddog/dd-opentracing-cpp/.build/RelWithDebInfo/dd_opentracing.lib and object C:/dev/ddog/dd-opentracing-cpp/.build/RelWithDebInfo/dd_opentracing.exp
tracer.obj : error LNK2019: unresolved external symbol gethostname referenced in function "class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __cdecl datadog::opentracing::`anonymous namespace'::reportingHostname(struct
datadog::opentracing::TracerOptions)" (?reportingHostname@?A0x5ef9dd98@opentracing@datadog@@YA?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@UTracerOptions@23@@Z) [C:\dev\ddog\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]
C:\dev\ddog\dd-opentracing-cpp\.build\RelWithDebInfo\dd_opentracing.dll : fatal error LNK1120: 1 unresolved externals [C:\dev\ddog\dd-opentracing-cpp\.build\dd_opentracing.vcxproj]

C:\dev\ddog\dd-opentracing-cpp\.build>

[buzz3791]

I worked around this issue with these changes:

PS C:\dev\ddog\dd-opentracing-cpp> git diff .\CMakeLists.txt                                                            diff --git a/CMakeLists.txt b/CMakeLists.txt
index fc121ca..3f602bb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -64,7 +64,7 @@ endif()
 if(BUILD_COVERAGE)
   set(COVERAGE_LIBRARIES gcov)
 endif()
-set(DATADOG_LINK_LIBRARIES ${OPENTRACING_LIB} ${CURL_LIBRARIES} Threads::Threads ${COVERAGE_LIBRARIES})
+set(DATADOG_LINK_LIBRARIES ws2_32 ${OPENTRACING_LIB} ${CURL_LIBRARIES} Threads::Threads ${COVERAGE_LIBRARIES})

 ## Shared lib
 if(BUILD_SHARED)
@@ -97,7 +97,7 @@ endif()
 if(BUILD_OBJECT)
   add_library(dd_opentracing-object OBJECT ${DD_OPENTRACING_SOURCES})
   add_sanitizers(dd_opentracing-object)
-  target_link_libraries(dd_opentracing-object ${CURL_LIBRARIES} Threads::Threads)
+  target_link_libraries(dd_opentracing-object ws2_32 ${CURL_LIBRARIES} Threads::Threads)
   set_property(TARGET dd_opentracing-object PROPERTY POSITION_INDEPENDENT_CODE ON)
   target_compile_definitions(dd_opentracing-object PUBLIC DD_OPENTRACING_OBJECT)
 endif()
PS C:\dev\ddog\dd-opentracing-cpp>

[dgoffredo]

Thanks, @buzz3791. See my comment in #265 (comment).

Let's leave both of these open for reference.