Fix $dumpvar multithreaded assert, broke last commit.

include/verilated.h

@@ -201,13 +201,19 @@ public:
     /// Check that the current thread ID is the same as the construction thread ID
     void check() VL_MT_UNSAFE_ONE {
         if (VL_UNCOVERABLE(m_threadid != VL_THREAD_ID())) {
-            fatal_different();  // LCOV_EXCL_LINE
+            if (m_threadid == 0) {
+                m_threadid = VL_THREAD_ID();
+            } else {
+                fatal_different();  // LCOV_EXCL_LINE
+            }
         }
     }
+    void changeThread() { m_threadid = 0; }  // Allow intentional change-of-thread
     static void fatal_different() VL_MT_SAFE;
 #else  // !VL_THREADED || !VL_DEBUG
 public:
     void check() {}
+    void changeThread() {}
 #endif
 };
 

include/verilated_fst_c.h

@@ -66,6 +66,7 @@ private:
 public:
     explicit VerilatedFst(void* fst=NULL);
     ~VerilatedFst() { if (m_fst == NULL) { fstWriterClose(m_fst); } }
+    void changeThread() { m_assertOne.changeThread(); }
     bool isOpen() const { return m_fst != NULL; }
     void open(const char* filename) VL_MT_UNSAFE;
     void flush() VL_MT_UNSAFE { fstWriterFlushContext(m_fst); }
@@ -199,6 +200,8 @@ class VerilatedFstC {
 public:
     explicit VerilatedFstC(void* filep=NULL) : m_sptrace(filep) {}
     ~VerilatedFstC() { close(); }
+    /// Routines can only be called from one thread; allow next call from different thread
+    void changeThread() { spTrace()->changeThread(); }
 public:
     // ACCESSORS
     /// Is file open?

include/verilated_vcd_c.h

@@ -159,6 +159,8 @@ private:
 public:
     explicit VerilatedVcd(VerilatedVcdFile* filep = NULL);
     ~VerilatedVcd();
+    /// Routines can only be called from one thread; allow next call from different thread
+    void changeThread() { m_assertOne.changeThread(); }
 
     // ACCESSORS
     /// Set size in megabytes after which new file should be created
@@ -446,6 +448,8 @@ public:
     explicit VerilatedVcdC(VerilatedVcdFile* filep = NULL)
         : m_sptrace(filep) {}
     ~VerilatedVcdC() { close(); }
+    /// Routines can only be called from one thread; allow next call from different thread
+    void changeThread() { spTrace()->changeThread(); }
 public:
     // ACCESSORS
     /// Is file open?

src/V3EmitC.cpp

@@ -3088,6 +3088,7 @@ class EmitCTrace : EmitCStmts {
             puts(    "const char* cp = vl_dumpctl_filenamep();\n");
             puts(    "trace(__VlSymsp->__Vm_dumperp, 0, 0);\n");
             puts(    "__VlSymsp->__Vm_dumperp->open(vl_dumpctl_filenamep());\n");
+            puts(    "__VlSymsp->__Vm_dumperp->changeThread();\n");
             puts(  "}\n");
             puts("}\n");
             splitSizeInc(10);