ICU-21064 Fix declspec macro conflict on clang.

diff --git a/icu4c/source/common/unicode/platform.h b/icu4c/source/common/unicode/platform.h
index cb3a833fefc9b1dc515cf55f8fd9b80f3543ee47..b7e514442cedba995977f3a22726f96af1d4718c 100644 (file)
--- a/icu4c/source/common/unicode/platform.h
+++ b/icu4c/source/common/unicode/platform.h
@@ -814,8 +814,8 @@ namespace std {
     /* Use the predefined value. */
 #elif defined(U_STATIC_IMPLEMENTATION)
 #   define U_EXPORT
-#elif defined(_MSC_VER) || (UPRV_HAS_DECLSPEC_ATTRIBUTE(dllexport) && \
-                            UPRV_HAS_DECLSPEC_ATTRIBUTE(dllimport))
+#elif defined(_MSC_VER) || (UPRV_HAS_DECLSPEC_ATTRIBUTE(__dllexport__) && \
+                            UPRV_HAS_DECLSPEC_ATTRIBUTE(__dllimport__))
 #   define U_EXPORT __declspec(dllexport)
 #elif defined(__GNUC__)
 #   define U_EXPORT __attribute__((visibility("default")))
@@ -839,8 +839,8 @@ namespace std {
 
 #ifdef U_IMPORT
     /* Use the predefined value. */
-#elif defined(_MSC_VER) || (UPRV_HAS_DECLSPEC_ATTRIBUTE(dllexport) && \
-                            UPRV_HAS_DECLSPEC_ATTRIBUTE(dllimport))
+#elif defined(_MSC_VER) || (UPRV_HAS_DECLSPEC_ATTRIBUTE(__dllexport__) && \
+                            UPRV_HAS_DECLSPEC_ATTRIBUTE(__dllimport__))
     /* Windows needs to export/import data. */
 #   define U_IMPORT __declspec(dllimport)
 #else