ICU-2787 add u_init() to work around thread safety problems with existing lazy init

X-SVN-Rev: 11735

icu4c/source/common/ucln_cmn.c

@@ -15,6 +15,7 @@
 */
 
 #include "unicode/uclean.h"
+#include "unicode/uchar.h"
 #include "ucln_cmn.h"
 #include "umutex.h"
 #include "ucln.h"
@@ -82,3 +83,46 @@ u_cleanup(void)
     umtx_destroy(NULL);
 }
 
+
+static UMTX     InitMutex = NULL;  
+
+U_CAPI void U_EXPORT2
+u_init(UErrorCode *status) {
+    /*
+     * Lock and unlock the global mutex, thus forcing into existence
+     *   if it hasn't already been created.
+     */
+    umtx_lock(NULL);
+    umtx_unlock(NULL);
+
+
+    /* Lock a private mutex for the duration of the initialization,
+     *  ensuring that there are no races through here, and to serve as
+     *  a memory barrier.  Don't use the global mutex, because of the 
+     *  possibility that some of the functions called within here might
+     *  use it.
+     */
+    umtx_lock(&InitMutex);
+
+    /*
+     *  Do a simple operation using each of the data-requiring APIs that do
+     *   not have a service object, ensuring that the required data is loaded.
+     */
+
+
+    /* Char Properties */
+    u_hasBinaryProperty(0x20, UCHAR_WHITE_SPACE);
+
+    /* Char Names  */
+    {
+        char buf[100];
+        u_charName(0x20, U_UNICODE_CHAR_NAME,  buf, 100,  status);
+    }
+
+
+    /*  TODO:  the rest of 'em  */
+
+
+    umtx_unlock(&InitMutex);
+
+}

icu4c/source/common/unicode/uclean.h

@@ -19,6 +19,31 @@
 
 #include "unicode/utypes.h"
 
+/**
+ *  Initialize ICU.  This function loads and initializes data items
+ *  that are required internally by various ICU functions.  Use of this explicit
+ *  initialization is required in multi-threaded applications; in 
+ *  single threaded apps, use is optional, but incurs little additional
+ *  cost, and is thus recommended.
+ *  <p>
+ *  In multi-threaded applications, u_init() should be called  in the
+ *  main thread before starting additional threads, or, alternatively
+ *  it can be called in each individual thread once, before other ICU
+ *  functions are called in that thread.  In this second scenario, the
+ *  application must guarantee that the first call to u_init() happen
+ *  without contention, in a single thread only.
+ *  <p>
+ *  Extra, repeated, or otherwise unneeded calls to u_init() do no harm,
+ *  other taking a small amount of time.
+ *
+ * @param pErrorCode An ICU UErrorCode parameter. It must not be <code>NULL</code>.
+ *    An Error will be retuned if some required part of ICU data can not
+ *    be loaded or initialized.
+ *
+ */  
+U_CAPI void U_EXPORT2 
+u_init(UErrorCode *status);
+
 /**
  * Clean up the system resources, such as allocated memory or open files,
  * used in all ICU libraries. This will free/delete all memory owned by the
@@ -39,10 +64,10 @@
  * results.
  * <p>
  * After calling u_cleanup(), an application may continue to use ICU by
- * creating an ICU C++ object or opening new items (converters, collators,
- * etc.) and using them.  An application must use ICU from one single
- * thread before allowing other threads or processes from using ICU.  This
- * is so that the ICU libraries can reinitialize in a thread safe manner.
+ * calling u_init().  An application must invoke u_init() first from one single
+ * thread before allowing other threads call u_init().  All threads existing
+ * at the time of the first thread's call to u_init() must also call
+ * u_init() themselves before continuing with other ICU operations.  
  * <p>
  * The use of u_cleanup() just before an application terminates is optional,
  * but it should be called only once for performance reasons. The primary

icu4c/source/test/intltest/intltest.cpp

@@ -1064,6 +1064,19 @@ main(int argc, char* argv[])
     fprintf(stdout, "   Leaks (l)             : %s\n", (leaks?      "On" : "Off"));
     fprintf(stdout, "-----------------------------------------------\n");
 
+    // Check that u_init() works
+    errorCode = U_ZERO_ERROR;
+    u_init(&errorCode);
+    if (U_FAILURE(errorCode)) {
+        fprintf(stdout,
+            "*** u_init() failed with error code = %s\n"
+                "*** Check the ICU_DATA environment variable and\n"
+                "*** check that the data files are present.\n",
+                u_errorName(errorCode));
+        return 1;
+    }
+
+
     // initial check for the default converter
     errorCode = U_ZERO_ERROR;
     cnv = ucnv_open(0, &errorCode);