Fix issue open-telemetry#834

Signed-off-by: owent <[email protected]>

CMakeLists.txt

@@ -50,7 +50,6 @@ option(WITH_STL "Whether to use Standard Library for C++latest features" OFF)
 option(WITH_ABSEIL "Whether to use Abseil for C++latest features" OFF)
 
 if(WITH_ABSEIL)
-  add_definitions(-DHAVE_ABSEIL)
   find_package(absl CONFIG REQUIRED)
 
   set(CORE_RUNTIME_LIBS absl::any absl::base absl::bits absl::city)

api/CMakeLists.txt

@@ -41,6 +41,10 @@ if(BUILD_TESTING)
   add_subdirectory(test)
 endif()
 
+if(WITH_ABSEIL)
+  target_compile_definitions(opentelemetry_api INTERFACE HAVE_ABSEIL)
+endif()
+
 if(WITH_STL)
   message("Building with standard library types...")
   target_compile_definitions(opentelemetry_api INTERFACE HAVE_CPP_STDLIB

api/include/opentelemetry/nostd/variant.h

@@ -47,7 +47,7 @@ OPENTELEMETRY_END_NAMESPACE
 #  endif
 
 #  ifdef HAVE_ABSEIL
-#    include "absl/types/variant.h"
+#    include <absl/types/variant.h>
 #  else
 #    include "./absl/types/variant.h"
 #  endif

sdk/src/common/core.cc

@@ -7,7 +7,7 @@
 #include "opentelemetry/nostd/variant.h"
 // clang-format on
 
-#if defined(HAVE_ABSEIL)
+#if !defined(HAVE_CPP_STDLIB) && !defined(OTABSL_USES_STD_VARIANT)
 /* The option of building and linking with Abseil library implies that Abseil
  * may already provide the ThrowBadVariantAccess implementation if its own.
  * Reconsider the implementation below: we are potentially introducing
@@ -28,9 +28,19 @@
 
 namespace absl
 {
+#  if defined(HAVE_ABSEIL)
+ABSL_NAMESPACE_BEGIN
+#  else
+OTABSL_NAMESPACE_BEGIN
+#  endif
 namespace variant_internal
 {
 void __cdecl ThrowBadVariantAccess(){/* TODO: std::terminate or re-throw? */};
 }
+#  if defined(HAVE_ABSEIL)
+ABSL_NAMESPACE_END
+#  else
+OTABSL_NAMESPACE_END
+#  endif
 }  // namespace absl
 #endif