Fix comments on the Parse.nMaxArgs field so that they are correct. Add

assert()s to ensure they are correct.  Other Parse changes to reduce the
amount of memset() needed to initialize it.

FossilOrigin-Name: c56092507c96723030589ddd9121bc993d615a7acd453305fc3b1dbb9e30554c

5 files changed, 32 insertions, 19 deletions

diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index acc36f07c..359ed1b6b 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -3823,19 +3823,20 @@ struct Parse {
   char *zErrMsg;       /* An error message */
   Vdbe *pVdbe;         /* An engine for executing database bytecode */
   int rc;              /* Return code from execution */
-  u8 colNamesSet;      /* TRUE after OP_ColumnName has been issued to pVdbe */
-  u8 checkSchema;      /* Causes schema cookie check after an error */
+  LogEst nQueryLoop;   /* Est number of iterations of a query (10*log2(N)) */
   u8 nested;           /* Number of nested calls to the parser/code generator */
   u8 nTempReg;         /* Number of temporary registers in aTempReg[] */
   u8 isMultiWrite;     /* True if statement may modify/insert multiple rows */
   u8 mayAbort;         /* True if statement may throw an ABORT exception */
   u8 hasCompound;      /* Need to invoke convertCompoundSelectToSubquery() */
-  u8 okConstFactor;    /* OK to factor out constants */
   u8 disableLookaside; /* Number of times lookaside has been disabled */
   u8 prepFlags;        /* SQLITE_PREPARE_* flags */
   u8 withinRJSubrtn;   /* Nesting level for RIGHT JOIN body subroutines */
-  u8 bHasWith;         /* True if statement contains WITH */
   u8 mSubrtnSig;       /* mini Bloom filter on available SubrtnSig.selId */
+  u8 eTriggerOp;       /* TK_UPDATE, TK_INSERT or TK_DELETE */
+  u8 bReturning;       /* Coding a RETURNING trigger */
+  u8 eOrconf;          /* Default ON CONFLICT policy for trigger steps */
+  u8 disableTriggers;  /* True to disable triggers */
 #if defined(SQLITE_DEBUG) || defined(SQLITE_COVERAGE_TEST)
   u8 earlyCleanup;     /* OOM inside sqlite3ParserAddCleanup() */
 #endif
@@ -3844,6 +3845,10 @@ struct Parse {
   u8 isCreate;         /* CREATE TABLE, INDEX, or VIEW (but not TRIGGER)
                        ** and ALTER TABLE ADD COLUMN. */
 #endif
+  u8 colNamesSet :1;   /* TRUE after OP_ColumnName has been issued to pVdbe */
+  u8 bHasWith :1;      /* True if statement contains WITH */
+  u8 okConstFactor :1; /* OK to factor out constants */
+  u8 checkSchema :1;   /* Causes schema cookie check after an error */
   int nRangeReg;       /* Size of the temporary register block */
   int iRangeReg;       /* First register in temporary register block */
   int nErr;            /* Number of errors seen */
@@ -3860,7 +3865,7 @@ struct Parse {
   IndexedExpr *pIdxPartExpr; /* Exprs constrained by index WHERE clauses */
   yDbMask writeMask;   /* Start a write transaction on these databases */
   yDbMask cookieMask;  /* Bitmask of schema verified databases */
-  int nMaxArg;         /* Max args passed to user function by sub-program */
+  int nMaxArg;         /* Max args to xUpdate and xFilter vtab methods */
   int nSelect;         /* Number of SELECT stmts. Counter for Select.selId */
 #ifndef SQLITE_OMIT_PROGRESS_CALLBACK
   u32 nProgressSteps;  /* xProgress steps taken during sqlite3_prepare() */
@@ -3874,11 +3879,6 @@ struct Parse {
   Table *pTriggerTab;  /* Table triggers are being coded for */
   TriggerPrg *pTriggerPrg;  /* Linked list of coded triggers */
   ParseCleanup *pCleanup;   /* List of cleanup operations to run after parse */
-  LogEst nQueryLoop;   /* Est number of iterations of a query (10*log2(N)) */
-  u8 eTriggerOp;       /* TK_UPDATE, TK_INSERT or TK_DELETE */
-  u8 bReturning;       /* Coding a RETURNING trigger */
-  u8 eOrconf;          /* Default ON CONFLICT policy for trigger steps */
-  u8 disableTriggers;  /* True to disable triggers */
 
   /**************************************************************************
   ** Fields above must be initialized to zero.  The fields that follow,
diff --git a/src/vdbe.c b/src/vdbe.c
index d41ac8d51..ec871c5a6 100644
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -8363,6 +8363,7 @@ case OP_VFilter: {   /* jump, ncycle */
 
   /* Invoke the xFilter method */
   apArg = p->apArg;
+  assert( nArg<=p->napArg );
   for(i = 0; i<nArg; i++){
     apArg[i] = &pArgc[i+1];
   }
@@ -8573,6 +8574,7 @@ case OP_VUpdate: {
     u8 vtabOnConflict = db->vtabOnConflict;
     apArg = p->apArg;
     pX = &aMem[pOp->p3];
+    assert( nArg<=p->napArg );
     for(i=0; i<nArg; i++){
       assert( memIsValid(pX) );
       memAboutToChange(p, pX);
diff --git a/src/vdbeInt.h b/src/vdbeInt.h
index 24cf1ac56..ecc757dd0 100644
--- a/src/vdbeInt.h
+++ b/src/vdbeInt.h
@@ -462,7 +462,7 @@ struct Vdbe {
   i64 nStmtDefCons;       /* Number of def. constraints when stmt started */
   i64 nStmtDefImmCons;    /* Number of def. imm constraints when stmt started */
   Mem *aMem;              /* The memory locations */
-  Mem **apArg;            /* Arguments to currently executing user function */
+  Mem **apArg;            /* Arguments xUpdate and xFilter vtab methods */
   VdbeCursor **apCsr;     /* One element of this array for each open cursor */
   Mem *aVar;              /* Values for the OP_Variable opcode. */
 
@@ -482,6 +482,7 @@ struct Vdbe {
 #ifdef SQLITE_DEBUG
   int rcApp;              /* errcode set by sqlite3_result_error_code() */
   u32 nWrite;             /* Number of write operations that have occurred */
+  int napArg;             /* Size of the apArg[] array */
 #endif
   u16 nResColumn;         /* Number of columns in one row of the result set */
   u16 nResAlloc;          /* Column slots allocated to aColName[] */
diff --git a/src/vdbeaux.c b/src/vdbeaux.c
index 81dca10f0..cf661eb9c 100644
--- a/src/vdbeaux.c
+++ b/src/vdbeaux.c
@@ -856,8 +856,8 @@ void sqlite3VdbeAssertAbortable(Vdbe *p){
 ** (1) For each jump instruction with a negative P2 value (a label)
 **     resolve the P2 value to an actual address.
 **
-** (2) Compute the maximum number of arguments used by any SQL function
-**     and store that value in *pMaxFuncArgs.
+** (2) Compute the maximum number of arguments used by the xUpdate/xFilter
+**     methods of any virtual table and store that value in *pMaxVtabArgs.
 **
 ** (3) Update the Vdbe.readOnly and Vdbe.bIsReader flags to accurately
 **     indicate what the prepared statement actually does.
@@ -870,8 +870,8 @@ void sqlite3VdbeAssertAbortable(Vdbe *p){
 ** script numbers the opcodes correctly.  Changes to this routine must be
 ** coordinated with changes to mkopcodeh.tcl.
 */
-static void resolveP2Values(Vdbe *p, int *pMaxFuncArgs){
-  int nMaxArgs = *pMaxFuncArgs;
+static void resolveP2Values(Vdbe *p, int *pMaxVtabArgs){
+  int nMaxVtabArgs = *pMaxVtabArgs;
   Op *pOp;
   Parse *pParse = p->pParse;
   int *aLabel = pParse->aLabel;
@@ -916,15 +916,19 @@ static void resolveP2Values(Vdbe *p, int *pMaxFuncArgs){
         }
 #ifndef SQLITE_OMIT_VIRTUALTABLE
         case OP_VUpdate: {
-          if( pOp->p2>nMaxArgs ) nMaxArgs = pOp->p2;
+          if( pOp->p2>nMaxVtabArgs ) nMaxVtabArgs = pOp->p2;
           break;
         }
         case OP_VFilter: {
           int n;
+          /* The instruction immediately prior to VFilter will be an
+          ** OP_Integer that sets the "argc" value for the VFilter.  See
+          ** the code where OP_VFilter is generated at tag-20250207a. */
           assert( (pOp - p->aOp) >= 3 );
           assert( pOp[-1].opcode==OP_Integer );
+          assert( pOp[-1].p2==pOp->p3+1 );
           n = pOp[-1].p1;
-          if( n>nMaxArgs ) nMaxArgs = n;
+          if( n>nMaxVtabArgs ) nMaxVtabArgs = n;
           /* Fall through into the default case */
           /* no break */ deliberate_fall_through
         }
@@ -965,7 +969,7 @@ resolve_p2_values_loop_exit:
     pParse->aLabel = 0;
   }
   pParse->nLabel = 0;
-  *pMaxFuncArgs = nMaxArgs;
+  *pMaxVtabArgs = nMaxVtabArgs;
   assert( p->bIsReader!=0 || DbMaskAllZero(p->btreeMask) );
 }
 
@@ -2643,7 +2647,7 @@ void sqlite3VdbeMakeReady(
   int nVar;                      /* Number of parameters */
   int nMem;                      /* Number of VM memory registers */
   int nCursor;                   /* Number of cursors required */
-  int nArg;                      /* Number of arguments in subprograms */
+  int nArg;                      /* Max number args to xFilter or xUpdate */
   int n;                         /* Loop counter */
   struct ReusableSpace x;        /* Reusable bulk memory */
 
@@ -2715,6 +2719,9 @@ void sqlite3VdbeMakeReady(
       p->apCsr = allocSpace(&x, p->apCsr, nCursor*sizeof(VdbeCursor*));
     }
   }
+#ifdef SQLITE_DEBUG
+  p->napArg = nArg;
+#endif
 
   if( db->mallocFailed ){
     p->nVar = 0;
diff --git a/src/wherecode.c b/src/wherecode.c
index 045653aac..1a0cdc6d7 100644
--- a/src/wherecode.c
+++ b/src/wherecode.c
@@ -1608,6 +1608,9 @@ Bitmask sqlite3WhereCodeOneLoopStart(
     }
     sqlite3VdbeAddOp2(v, OP_Integer, pLoop->u.vtab.idxNum, iReg);
     sqlite3VdbeAddOp2(v, OP_Integer, nConstraint, iReg+1);
+    /* The instruction immediately prior to OP_VFilter must be an OP_Integer
+    ** that sets the "argc" value for xVFilter.  This is necessary for
+    ** resolveP2() to work correctly.  See tag-20250207a. */
     sqlite3VdbeAddOp4(v, OP_VFilter, iCur, addrNotFound, iReg,
                       pLoop->u.vtab.idxStr,
                       pLoop->u.vtab.needFree ? P4_DYNAMIC : P4_STATIC);