Fix `final` asserts and $stop (#7249)

include/verilated.cpp

@@ -164,7 +164,10 @@ void vl_finish(const char* filename, int linenum, const char* hier) VL_MT_UNSAFE
 #ifndef VL_USER_STOP  ///< Define this to override the vl_stop function
 void vl_stop(const char* filename, int linenum, const char* hier) VL_MT_UNSAFE {
     // $stop or $fatal reporting; would break current API to add param as to which
-    if (Verilated::threadContextp()->gotFinish()) return;
+    if (Verilated::threadContextp()->gotFinish()
+        && !Verilated::threadContextp()->executingFinal()) {
+        return;
+    }
     const char* const msg = "Verilog $stop";
     Verilated::threadContextp()->gotError(true);
     Verilated::threadContextp()->gotFinish(true);
@@ -2831,6 +2834,14 @@ void VerilatedContext::gotFinish(bool flag) VL_MT_SAFE {
     const VerilatedLockGuard lock{m_mutex};
     m_s.m_gotFinish = flag;
 }
+bool VerilatedContext::executingFinal() const VL_MT_SAFE {
+    const VerilatedLockGuard lock{m_mutex};
+    return m_ns.m_executingFinal;
+}
+void VerilatedContext::executingFinal(bool flag) VL_MT_SAFE {
+    const VerilatedLockGuard lock{m_mutex};
+    m_ns.m_executingFinal = flag;
+}
 void VerilatedContext::profExecStart(uint64_t flag) VL_MT_SAFE {
     const VerilatedLockGuard lock{m_mutex};
     m_ns.m_profExecStart = flag;

include/verilated.h

@@ -408,6 +408,7 @@ protected:
     struct NonSerialized final {  // Non-serialized information
         // These are reloaded from on command-line settings, so do not need to persist
         // Fast path
+        bool m_executingFinal = false;  // Running generated final() code
         uint64_t m_profExecStart = 1;  // +prof+exec+start time
         uint32_t m_profExecWindow = 2;  // +prof+exec+window size
         // Slow path
@@ -530,6 +531,10 @@ public:
     bool gotFinish() const VL_MT_SAFE { return m_s.m_gotFinish; }
     /// Set if got a $finish or $stop/error
     void gotFinish(bool flag) VL_MT_SAFE;
+    /// Check if generated final() code is executing
+    bool executingFinal() const VL_MT_SAFE;
+    /// Set if generated final() code is executing
+    void executingFinal(bool flag) VL_MT_SAFE;
     /// Return if quiet enabled
     bool quiet() const VL_MT_SAFE { return m_s.m_quiet; }
     /// Enable quiet (also prevents need for OS calls to get CPU time)

src/V3EmitCModel.cpp

@@ -489,7 +489,9 @@ class EmitCModel final : public EmitCFunc {
               "void " + topModNameProtected + "__" + protect("_eval_final") + selfDecl + ";\n");
         // ::final
         puts("\nVL_ATTR_COLD void " + EmitCUtil::topClassName() + "::final() {\n");
+        puts("contextp()->executingFinal(true);\n");
         puts(/**/ topModNameProtected + "__" + protect("_eval_final") + "(&(vlSymsp->TOP));\n");
+        puts("contextp()->executingFinal(false);\n");
         puts("}\n");
 
         putSectionDelimiter("Implementations of abstract methods from VerilatedModel\n");

test_regress/t/t_final_assert.out

@@ -0,0 +1,3 @@
+[10] %Error: t_final_assert.v:12: Assertion failed in top.tb: 'assert' failed.
+%Error: t/t_final_assert.v:12: Verilog $stop
+Aborting...

test_regress/t/t_final_assert.py

@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# This program is free software; you can redistribute it and/or modify it
+# under the terms of either the GNU Lesser General Public License Version 3
+# or the Perl Artistic License Version 2.0.
+# SPDX-FileCopyrightText: 2024 Wilson Snyder
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('simulator')
+
+test.compile()
+
+test.execute(fails=True, expect_filename=test.golden_filename)
+
+test.passes()

test_regress/t/t_final_assert.v

@@ -0,0 +1,14 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain.
+// SPDX-FileCopyrightText: 2026 Antmicro
+// SPDX-License-Identifier: CC0-1.0
+
+module tb();
+    initial begin
+        $finish();
+    end
+    final begin
+        assert(1 == 0);
+    end
+endmodule