test/jtreg-ext/requires/VMProps.java

rev 59593 : [mq]: 8246494

*** 29,42 ****
--- 29,44 ----
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.nio.file.Paths;
  import java.nio.file.StandardOpenOption;
  import java.util.ArrayList;
+ import java.util.Collections;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Properties;
+ import java.util.Set;
  import java.util.concurrent.Callable;
  import java.util.concurrent.TimeUnit;
  import java.util.function.Supplier;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
*** 113,122 ****
--- 115,125 ----
          map.put("vm.compiler1.enabled", this::isCompiler1Enabled);
          map.put("vm.compiler2.enabled", this::isCompiler2Enabled);
          map.put("docker.support", this::dockerSupport);
          map.put("release.implementor", this::implementor);
          map.put("test.vm.gc.nvdimm", this::isNvdimmTestEnabled);
+         map.put("vm.flagless", this::isFlagless);
          vmGC(map); // vm.gc.X = true/false
          vmOptFinalFlags(map);
  
          dump(map.map);
          return map.map;
*** 500,509 ****
--- 503,571 ----
          String isEnabled = System.getenv("TEST_VM_GC_NVDIMM");
          return "" + "true".equalsIgnoreCase(isEnabled);
      }
  
      /**
+      * Checks if we are in <i>almost</i> out-of-box configuration, i.e. the flags
+      * which JVM is started with don't affect its behavior "significantly".
+      * {@code TEST_VM_FLAGLESS} enviroment variable can be used to force this
+      * method to return true and allow any flags.
+      *
+      * @return true if there are no JVM flags
+      */
+     private String isFlagless() {
+         boolean result = true;
+         if (System.getenv("TEST_VM_FLAGLESS") != null) {
+             return "" + result;
+         }
+ 
+         List<String> allFlags = new ArrayList<String>();
+         Collections.addAll(allFlags, System.getProperty("test.vm.opts", "").trim().split("\\s+"));
+         Collections.addAll(allFlags, System.getProperty("test.java.opts", "").trim().split("\\s+"));
+ 
+         // check -XX flags
+         var ignoredXXFlags = Set.of(
+                 // added by run-test framework
+                 "MaxRAMPercentage",
+                 // added by test environment
+                 "CreateCoredumpOnCrash"
+         );
+         result &= allFlags.stream()
+                           .filter(s -> s.startsWith("-XX:"))
+                           // map to names:
+                               // remove -XX:
+                               .map(s -> s.substring(4))
+                               // remove +/- from bool flags
+                               .map(s -> s.charAt(0) == '+' || s.charAt(0) == '-' ? s.substring(1) : s)
+                               // remove =.* from others
+                               .map(s -> s.contains("=") ? s.substring(0, s.indexOf('=')) : s)
+                           // skip known-to-be-there flags
+                           .filter(s -> !ignoredXXFlags.contains(s))
+                           .findAny()
+                           .isEmpty();
+ 
+         // check -X flags
+         var ignoredXFlags = Set.of(
+                 // default, yet still seen to be explicitly set
+                 "mixed"
+         );
+         result &= allFlags.stream()
+                           .filter(s -> s.startsWith("-X") && !s.startsWith("-XX:"))
+                           // map to names:
+                               // remove -X
+                               .map(s -> s.substring(2))
+                               // remove :.* from flags with values
+                               .map(s -> s.contains(":") ? s.substring(0, s.indexOf(':')) : s)
+                           // skip known-to-be-there flags
+                           .filter(s -> !ignoredXFlags.contains(s))
+                           .findAny()
+                           .isEmpty();
+ 
+         return "" + result;
+     }
+ 
+     /**
       * Dumps the map to the file if the file name is given as the property.
       * This functionality could be helpful to know context in the real
       * execution.
       *
       * @param map