[flags] introduce --allow-overwriting-for-next-flag

Bug: v8:10942
Change-Id: Icbb1d8e054ee924a77f1fbeb9e48cde604ef69b1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2422001
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70130}

src/flags/flag-definitions.h

@@ -227,6 +227,12 @@ DEFINE_BOOL(abort_on_contradictory_flags, false,
 // This implication is also hard-coded into the flags processing to make sure it
 // becomes active before we even process subsequent flags.
 DEFINE_NEG_IMPLICATION(fuzzing, abort_on_contradictory_flags)
+// This is not really a flag, it affects the interpretation of the next flag but
+// doesn't become permanently true when specified. This only works for flags
+// defined in this file, but not for d8 flags defined in src/d8/d8.cc.
+DEFINE_BOOL(allow_overwriting_for_next_flag, false,
+            "temporary disable flag contradiction to allow overwriting just "
+            "the next flag")
 
 // Flags for language modes and experimental language features.
 DEFINE_BOOL(use_strict, false, "enforce strict mode")

src/flags/flags.cc

@@ -213,6 +213,13 @@ struct Flag {
   }
 
   static bool ShouldCheckFlagContradictions() {
+    if (FLAG_allow_overwriting_for_next_flag) {
+      // Setting the flag manually to false before calling Reset() avoids this
+      // becoming re-entrant.
+      FLAG_allow_overwriting_for_next_flag = false;
+      FindFlagByPointer(&FLAG_allow_overwriting_for_next_flag)->Reset();
+      return false;
+    }
     return FLAG_abort_on_contradictory_flags && !FLAG_fuzzing;
   }
 
@@ -268,9 +275,17 @@ struct Flag {
                 name(), implied_by, hint);
           } else if (new_set_by == SetBy::kCommandLine &&
                      check_command_line_flags) {
-            FATAL(
-                "Command-line provided flag --%s specified multiple times.\n%s",
-                name(), hint);
+            if (is_bool_flag) {
+              FATAL(
+                  "Command-line provided flag --%s specified as both true and "
+                  "false.\n%s",
+                  name(), hint);
+            } else {
+              FATAL(
+                  "Command-line provided flag --%s specified multiple "
+                  "times.\n%s",
+                  name(), hint);
+            }
           }
           break;
       }

test/mjsunit/ensure-growing-store-learns.js

@@ -2,14 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// The flags are processed left to right. --no-abort-on-contradictory-flags
-// disables the checking for conflicts, then we process --noverify-heap and
+// Overwrite the value for --noverify-heap and
 // --noenable-slow-asserts, which the test runner already set to true before.
-// This causes the flags to be overwritten while silencing the error. Then we
-// re-enable --abort-on-contradictory-flags to make sure that the processing of
-// other flags and flag implications, which happens later, still produces
-// errors.
-// Flags: --no-abort-on-contradictory-flags --noverify-heap --noenable-slow-asserts --abort-on-contradictory-flags
+//  Due to flag contradiction checking, this requires
+// --allow-overwriting-for-next-flag to avoid an error.
+// Flags: --allow-overwriting-for-next-flag --noverify-heap
+// Flags: --allow-overwriting-for-next-flag --noenable-slow-asserts
 // Flags: --allow-natives-syntax --opt --no-always-opt
 
 // --noverify-heap and --noenable-slow-asserts are set because the test is too

test/mjsunit/mjsunit.status

@@ -865,13 +865,6 @@
   'harmony/atomics-waitasync-worker-shutdown-before-wait-finished-no-timeout': [SKIP],
 }],  # 'isolates'
 
-##############################################################################
-['deopt_fuzzer or gc_fuzzer', {
-  # https://crbug.com/v8/10942
-  'ensure-growing-store-learns': [SKIP],
-  'random-bit-correlations': [SKIP],
-}],  # 'deopt_fuzzer or gc_fuzzer'
-
 ##############################################################################
 ['deopt_fuzzer', {
 

test/mjsunit/random-bit-correlations.js

@@ -3,13 +3,9 @@
 // found in the LICENSE file.
 
 // Overwrite the random seed provided by the test runner to make this test less
-// flaky.
-// The flags are processed left to right. --no-abort-on-contradictory-flags
-// disables the checking for conflicts, then we process --random-seed=20 to
-// overwrite the value the test runner already set before. Then we re-enable
-// --abort-on-contradictory-flags to make sure that the processing of other
-// flags and flag implications, which happens later, still produces errors.
-// Flags: --no-abort-on-contradictory-flags --random-seed=20 --abort-on-contradictory-flags
+// flaky. Due to flag contradiction checking, this requires
+// --allow-overwriting-for-next-flag to avoid an error.
+// Flags: --allow-overwriting-for-next-flag --random-seed=20
 // Flags: --nostress-opt --noalways-opt --predictable
 
 (function() {