8380993: [REDO] Incorrect Interpretation of POSIX TZ Environment Variable on AIX

src/java.base/unix/native/libjava/TimeZone_md.c

@@ -352,33 +352,15 @@ getPlatformTimeZoneID()
 }
 
 static char *
-mapPlatformToJavaTimezone(const char *java_home_dir, const char *tz) {
+getJavaTimezoneFromPlatform(const char *tz_buf, size_t tz_len, const char *mapfilename) {
     FILE *tzmapf;
-    char mapfilename[PATH_MAX + 1];
     char line[256];
     int linecount = 0;
-    char *tz_buf = NULL;
-    char *temp_tz = NULL;
     char *javatz = NULL;
-    size_t tz_len = 0;
-
-    /* On AIX, the TZ environment variable may end with a comma
-     * followed by modifier fields until early AIX6.1.
-     * This restriction has been removed from AIX7. */
 
-    tz_buf = strdup(tz);
-    tz_len = strlen(tz_buf);
-
-    /* Open tzmappings file, with buffer overrun check */
-    if ((strlen(java_home_dir) + 15) > PATH_MAX) {
-        jio_fprintf(stderr, "Path %s/lib/tzmappings exceeds maximum path length\n", java_home_dir);
-        goto tzerr;
-    }
-    strcpy(mapfilename, java_home_dir);
-    strcat(mapfilename, "/lib/tzmappings");
     if ((tzmapf = fopen(mapfilename, "r")) == NULL) {
         jio_fprintf(stderr, "can't open %s\n", mapfilename);
-        goto tzerr;
+        return NULL;
     }
 
     while (fgets(line, sizeof(line), tzmapf) != NULL) {
@@ -431,10 +413,58 @@ mapPlatformToJavaTimezone(const char *java_home_dir, const char *tz) {
             break;
         }
     }
+
     (void) fclose(tzmapf);
+    return javatz;
+}
+
+static char *
+mapPlatformToJavaTimezone(const char *java_home_dir, const char *tz) {
+    char mapfilename[PATH_MAX + 1];
+    char *tz_buf = NULL;
+    char *javatz = NULL;
+    char *temp_tz = NULL;
+    size_t tz_len = 0;
+
+    /* On AIX, the TZ environment variable may end with a comma
+     * followed by modifier fields until early AIX6.1.
+     * This restriction has been removed from AIX7. */
+
+    tz_buf = strdup(tz);
+    if (tz_buf == NULL) {
+        jio_fprintf(stderr, "Failed to allocate timezone buffer\n");
+        goto tzerr;
+    }
+    tz_len = strlen(tz_buf);
+
+    /* Open tzmappings file, with buffer overrun check */
+    if ((strlen(java_home_dir) + 15) > PATH_MAX) {
+        jio_fprintf(stderr, "Path %s/lib/tzmappings exceeds maximum path length\n", java_home_dir);
+        goto tzerr;
+    }
+    strcpy(mapfilename, java_home_dir);
+    strcat(mapfilename, "/lib/tzmappings");
+
+    // First attempt to find the Java timezone for the full tz string
+    javatz = getJavaTimezoneFromPlatform(tz_buf, tz_len, mapfilename);
+
+    // If no match was found, check for timezone with truncated value
+    if (javatz == NULL) {
+        temp_tz = strchr(tz, ',');
+        tz_len = (temp_tz == NULL) ? strlen(tz) : temp_tz - tz;
+        free((void *) tz_buf);
+        tz_buf = (char *)malloc(tz_len + 1);
+        if (tz_buf == NULL) {
+            jio_fprintf(stderr, "Failed to allocate timezone buffer\n");
+            goto tzerr;
+        }
+        memcpy(tz_buf, tz, tz_len);
+        tz_buf[tz_len] = '\0';
+        javatz = getJavaTimezoneFromPlatform(tz_buf, tz_len, mapfilename);
+    }
 
 tzerr:
-    if (tz_buf != NULL ) {
+    if (tz_buf != NULL) {
         free((void *) tz_buf);
     }
 

test/jdk/java/util/TimeZone/AIXTzMappingTest.java

@@ -0,0 +1,102 @@
+/*
+ * Copyright (c) 2026, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/* @test
+ * @bug 8380993
+ * @library /test/lib
+ * @summary Validates AIX timezone mapping behavior where POSIX TZ strings
+ * with comma-separated DST rules are truncated and mapped through tzmappings
+ * to the expected IANA timezone IDs.
+ * @requires os.family == "aix"
+ * @run main/othervm AIXTzMappingTest
+ */
+
+import java.util.TimeZone;
+
+import jdk.test.lib.process.ProcessTools;
+import jdk.test.lib.process.OutputAnalyzer;
+
+public class AIXTzMappingTest {
+
+    // POSIX TZ strings that should be mapped via tzmappings
+    private static final String TZ_CET = "CET-1CEST,M3.5.0,M10.5.0";
+    private static final String TZ_MEZ = "MEZ-1MESZ,M3.5.0,M10.5.0/3";
+
+    private static final String ID_PARIS = "Europe/Paris";
+    private static final String ID_BERLIN = "Europe/Berlin";
+
+    public static void main(String[] args) throws Throwable {
+        if (args.length == 0) {
+            runWithTZ(TZ_CET, ID_PARIS);
+            runWithTZ(TZ_MEZ, ID_BERLIN);
+        } else if (args.length == 1) {
+            runTZTest(args[0]);
+        } else {
+            throw new RuntimeException(
+                    "Expected 0 or 1 arguments, got " + args.length);
+        }
+    }
+
+    private static void runWithTZ(String tz, String expectedId)
+            throws Throwable {
+        ProcessBuilder pb = ProcessTools.createTestJavaProcessBuilder(
+                "AIXTzMappingTest", expectedId);
+
+        pb.environment().put("TZ", tz);
+
+        OutputAnalyzer output = ProcessTools.executeProcess(pb);
+        output.shouldHaveExitValue(0);
+    }
+
+    /*
+     * On AIX, POSIX TZ strings such as:
+     *     CET-1CEST,M3.5.0,M10.5.0
+     *     MEZ-1MESZ,M3.5.0,M10.5.0/3
+     * are truncated at the comma and mapped through tzmappings to
+     * IANA timezone IDs.
+     *
+     * This test verifies that the expected IANA timezone ID is selected.
+     */
+    private static void runTZTest(String expectedId) {
+        String tzStr = System.getenv("TZ");
+
+        if (tzStr == null) {
+            throw new RuntimeException(
+                    "Got unexpected timezone information: TZ is null");
+        }
+
+        TimeZone tz = TimeZone.getDefault();
+        String tzId = tz.getID();
+
+        if (!expectedId.equals(tzId)) {
+            throw new RuntimeException(
+                    "Expected timezone ID " + expectedId
+                    + " but got " + tzId
+                    + " for TZ=" + tzStr);
+        }
+
+        System.out.println(
+                "AIX timezone mapping test passed: "
+                + tzId + " for TZ=" + tzStr);
+    }
+}

test/jdk/java/util/TimeZone/CustomTzIDCheckDST.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2022, 2026, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -26,7 +26,10 @@
  * @library /test/lib
  * @summary This test will ensure that daylight savings rules are followed
  * appropriately when setting a custom timezone ID via the TZ env variable.
- * @requires os.family != "windows"
+ * AIX is excluded because it uses a different timezone mapping mechanism
+ * through the tzmappings file; see AIXTzMappingTest.java for AIX-specific
+ * coverage.
+ * @requires os.family != "windows" & os.family != "aix"
  * @run main/othervm CustomTzIDCheckDST
  */