ICU-20530 Fix header issues based on test/hdrtst

Remove explicit extern "C++" scope.

Remove C++ macros in C mode.

Fix issues detected by make -C test/hdrtst.

Run test/hdrtest during CI to detect future breakage.

Signed-off-by: Alon Bar-Lev <alon.barlev@gmail.com>

.travis.yml

@@ -41,18 +41,23 @@ matrix:
     #
     # Test both out-of-source and in-source builds. This one (gcc) for out-of-source,
     # and linux clang (below) for in-source.
+    #
+    # Invokes test/hdrtst to check public headers compliance.
 
     - name: "c: linux gcc"
       language: cpp
       compiler: gcc
+      env:      PREFIX=/tmp/icu-prefix
       before_script:
         - mkdir build
         - cd build
-        - ../icu4c/source/runConfigureICU --enable-debug --disable-release Linux
+        - ../icu4c/source/runConfigureICU --enable-debug --disable-release Linux --prefix="${PREFIX}"
         - make -j2
       script:
         - make -j2 check
         - ( cd ../icu4c/source/test/depstest && ./depstest.py ../../../../build/ )
+        - make install
+        - PATH="${PREFIX}/bin:$PATH" make -C test/hdrtst check
 
     - name: "c: linux clang"
       language: cpp

icu4c/source/common/unicode/ucptrie.h

@@ -216,25 +216,6 @@ ucptrie_openFromBinary(UCPTrieType type, UCPTrieValueWidth valueWidth,
 U_CAPI void U_EXPORT2
 ucptrie_close(UCPTrie *trie);
 
-#if U_SHOW_CPLUSPLUS_API
-
-U_NAMESPACE_BEGIN
-
-/**
- * \class LocalUCPTriePointer
- * "Smart pointer" class, closes a UCPTrie via ucptrie_close().
- * For most methods see the LocalPointerBase base class.
- *
- * @see LocalPointerBase
- * @see LocalPointer
- * @draft ICU 63
- */
-U_DEFINE_LOCAL_OPEN_POINTER(LocalUCPTriePointer, UCPTrie, ucptrie_close);
-
-U_NAMESPACE_END
-
-#endif
-
 /**
  * Returns the trie type.
  *
@@ -642,5 +623,25 @@ ucptrie_internalU8PrevIndex(const UCPTrie *trie, UChar32 c,
 U_CDECL_END
 
 #endif  // U_IN_DOXYGEN
+
+#if U_SHOW_CPLUSPLUS_API
+
+U_NAMESPACE_BEGIN
+
+/**
+ * \class LocalUCPTriePointer
+ * "Smart pointer" class, closes a UCPTrie via ucptrie_close().
+ * For most methods see the LocalPointerBase base class.
+ *
+ * @see LocalPointerBase
+ * @see LocalPointer
+ * @draft ICU 63
+ */
+U_DEFINE_LOCAL_OPEN_POINTER(LocalUCPTriePointer, UCPTrie, ucptrie_close);
+
+U_NAMESPACE_END
+
+#endif  // U_SHOW_CPLUSPLUS_API
+
 #endif  // U_HIDE_DRAFT_API
 #endif

icu4c/source/common/unicode/udata.h

@@ -264,25 +264,6 @@ udata_openChoice(const char *path, const char *type, const char *name,
 U_STABLE void U_EXPORT2
 udata_close(UDataMemory *pData);
 
-#if U_SHOW_CPLUSPLUS_API
-
-U_NAMESPACE_BEGIN
-
-/**
- * \class LocalUDataMemoryPointer
- * "Smart pointer" class, closes a UDataMemory via udata_close().
- * For most methods see the LocalPointerBase base class.
- *
- * @see LocalPointerBase
- * @see LocalPointer
- * @stable ICU 4.4
- */
-U_DEFINE_LOCAL_OPEN_POINTER(LocalUDataMemoryPointer, UDataMemory, udata_close);
-
-U_NAMESPACE_END
-
-#endif
-
 /**
  * Get the pointer to the actual data inside the data memory.
  * The data is read-only.
@@ -434,4 +415,23 @@ udata_setFileAccess(UDataFileAccess access, UErrorCode *status);
 
 U_CDECL_END
 
+#if U_SHOW_CPLUSPLUS_API
+
+U_NAMESPACE_BEGIN
+
+/**
+ * \class LocalUDataMemoryPointer
+ * "Smart pointer" class, closes a UDataMemory via udata_close().
+ * For most methods see the LocalPointerBase base class.
+ *
+ * @see LocalPointerBase
+ * @see LocalPointer
+ * @stable ICU 4.4
+ */
+U_DEFINE_LOCAL_OPEN_POINTER(LocalUDataMemoryPointer, UDataMemory, udata_close);
+
+U_NAMESPACE_END
+
+#endif  // U_SHOW_CPLUSPLUS_API
+
 #endif

icu4c/source/common/unicode/uversion.h

@@ -62,36 +62,29 @@ typedef uint8_t UVersionInfo[U_MAX_VERSION_LENGTH];
 /* C++ namespace if supported. Versioned unless versioning is disabled.      */
 /*===========================================================================*/
 
+/* Define C++ namespace symbols. */
+#ifdef __cplusplus
+
 /**
  * \def U_NAMESPACE_BEGIN
- * This is used to begin a declaration of a public ICU C++ API.
- * When not compiling for C++, it does nothing.
- * When compiling for C++, it begins an extern "C++" linkage block (to protect
- * against cases in which an external client includes ICU header files inside
- * an extern "C" linkage block).
+ * This is used to begin a declaration of a public ICU C++ API within
+ * versioned-ICU-namespace block.
  *
- * It also begins a versioned-ICU-namespace block.
  * @stable ICU 2.4
  */
 
 /**
  * \def U_NAMESPACE_END
  * This is used to end a declaration of a public ICU C++ API.
- * When not compiling for C++, it does nothing.
- * When compiling for C++, it ends the extern "C++" block begun by
- * U_NAMESPACE_BEGIN.
+ * It ends the versioned-ICU-namespace block begun by U_NAMESPACE_BEGIN.
  *
- * It also ends the versioned-ICU-namespace block begun by U_NAMESPACE_BEGIN.
  * @stable ICU 2.4
  */
 
 /**
  * \def U_NAMESPACE_USE
  * This is used to specify that the rest of the code uses the
  * public ICU C++ API namespace.
- * This is invoked by default; we recommend that you turn it off:
- * See the "Recommended Build Options" section of the ICU4C readme
- * (http://source.icu-project.org/repos/icu/icu/trunk/readme.html#RecBuild)
  * @stable ICU 2.4
  */
 
@@ -105,8 +98,6 @@ typedef uint8_t UVersionInfo[U_MAX_VERSION_LENGTH];
  * @stable ICU 2.4
  */
 
-/* Define C++ namespace symbols. */
-#ifdef __cplusplus
 #   if U_DISABLE_RENAMING
 #       define U_ICU_NAMESPACE icu
         namespace U_ICU_NAMESPACE { }
@@ -116,8 +107,8 @@ typedef uint8_t UVersionInfo[U_MAX_VERSION_LENGTH];
         namespace icu = U_ICU_NAMESPACE;
 #   endif
 
-#   define U_NAMESPACE_BEGIN extern "C++" { namespace U_ICU_NAMESPACE {
-#   define U_NAMESPACE_END } }
+#   define U_NAMESPACE_BEGIN namespace U_ICU_NAMESPACE {
+#   define U_NAMESPACE_END }
 #   define U_NAMESPACE_USE using namespace U_ICU_NAMESPACE;
 #   define U_NAMESPACE_QUALIFIER U_ICU_NAMESPACE::
 
@@ -133,12 +124,7 @@ typedef uint8_t UVersionInfo[U_MAX_VERSION_LENGTH];
 #   if U_USING_ICU_NAMESPACE
         U_NAMESPACE_USE
 #   endif
-#else
-#   define U_NAMESPACE_BEGIN
-#   define U_NAMESPACE_END
-#   define U_NAMESPACE_USE
-#   define U_NAMESPACE_QUALIFIER
-#endif
+#endif /* __cplusplus */
 
 /*===========================================================================*/
 /* General version helper functions. Definitions in putil.c                  */

icu4c/source/i18n/unicode/reldatefmt.h

@@ -246,6 +246,7 @@ class SharedPluralRules;
 class SharedBreakIterator;
 class NumberFormat;
 class UnicodeString;
+class FormattedRelativeDateTime;
 class FormattedRelativeDateTimeData;
 
 #ifndef U_HIDE_DRAFT_API