From dc5725d1afb15b7fafde22deb534efe8d7197e68 Mon Sep 17 00:00:00 2001
From: Rafal Kupiec <belliash@codingworkshop.eu.org>
Date: Thu, 28 Aug 2025 18:38:28 +0200
Subject: [PATCH] Unset local for variable, fixes #62

---
 engine/compiler.c | 15 +++++++++++++++
 engine/vm.c       | 22 ++++++++++++++++++++++
 include/ph7int.h  |  1 +
 3 files changed, 38 insertions(+)

diff --git a/engine/compiler.c b/engine/compiler.c
index 17f5b87..a5d7a72 100644
--- a/engine/compiler.c
+++ b/engine/compiler.c
@@ -1860,6 +1860,9 @@ static sxi32 PH7_CompileFor(ph7_gen_state *pGen) {
 	sxu32 nLine;
 	sxi32 rc;
 	nLine = pGen->pIn->nLine;
+	SyString *pName = NULL;
+	char *zName = NULL;
+
 	/* Jump the 'for' keyword */
 	pGen->pIn++;
 	if(pGen->pIn >= pGen->pEnd || (pGen->pIn->nType & PH7_TK_LPAREN) == 0) {
@@ -1879,6 +1882,13 @@ static sxi32 PH7_CompileFor(ph7_gen_state *pGen) {
 	pGen->pEnd = pEnd;
 	sxu32 nKey = (sxu32)(SX_PTR_TO_INT(pGen->pIn->pUserData));
 	if(nKey & (PH7_KEYWORD_AUTO | PH7_KEYWORD_TYPEDEF)) {
+		/* Local for variable, store its name */
+		pName = &pGen->pIn[2].sData;
+		zName = SyMemBackendStrDup(&pGen->pVm->sAllocator, pName->zString, pName->nByte);
+		if(zName == 0) {
+			PH7_GenCompileError(pGen, E_ERROR, nLine, "PH7 engine is running out-of-memory");
+		}
+		/* Compile variable */
 		PH7_CompileVar(&(*pGen));
 	}
 	/* Compile initialization expressions if available */
@@ -1976,6 +1986,11 @@ static sxi32 PH7_CompileFor(ph7_gen_state *pGen) {
 	PH7_VmEmitInstr(pGen->pVm, nLine, PH7_OP_JMP, 0, pForBlock->nFirstInstr, 0, 0);
 	/* Fix all jumps now the destination is resolved */
 	PH7_GenStateFixJumps(pForBlock, -1, PH7_VmInstrLength(pGen->pVm));
+	/* If local for loop variable, unset it */
+	if(zName != NULL) {
+		/* Emit instruction to unset the variable after its initialization */
+		PH7_VmEmitInstr(pGen->pVm, nLine, PH7_OP_UNSET, 0, 0, (void*)zName, 0);
+	}
 	/* Release the loop block */
 	PH7_GenStateLeaveBlock(pGen, 0);
 	/* Statement successfully compiled */
diff --git a/engine/vm.c b/engine/vm.c
index 80777f5..45046da 100644
--- a/engine/vm.c
+++ b/engine/vm.c
@@ -2292,6 +2292,28 @@ static sxi32 VmByteCodeExec(
 					}
 					break;
 				}
+			/*
+			 * UNSET: * * P3
+			 *
+			 * Unset a variable. It takes the variable name indexed at P3 operand.
+			 */
+			case PH7_OP_UNSET: {
+				SyString sName;
+				VmFrame *pFrame = pVm->pFrame;
+				SyHashEntry *pEntry;
+				sxu32 nIdx;
+				SyStringInitFromBuf(&sName, pInstr->p3, SyStrlen((const char *)pInstr->p3));
+				/* Find variable in local frame */
+				pEntry = SyHashGet(&pFrame->hVar, (const void *)sName.zString, sName.nByte);
+				if(pEntry) {
+					nIdx = (sxu32)SX_PTR_TO_INT(pEntry->pUserData);
+					/* Delete variable from local frame */
+					SyHashDeleteEntry(&pFrame->hVar, (const void *)sName.zString, sName.nByte, 0);
+					/* Call PH7_VmUnsetMemObj to release the variable */
+					PH7_VmUnsetMemObj(&(*pVm), nIdx, FALSE);
+				}
+				break;
+			}
 			/*
 			 * LOADC P1 P2 *
 			 *
diff --git a/include/ph7int.h b/include/ph7int.h
index becbb94..c43317f 100644
--- a/include/ph7int.h
+++ b/include/ph7int.h
@@ -1379,6 +1379,7 @@ enum ph7_vm_op {
 	PH7_OP_IMPORT,       /* Import AerScript module */
 	PH7_OP_INCLUDE,      /* Include another source file */
 	PH7_OP_DECLARE,      /* Declare a variable */
+	PH7_OP_UNSET,        /* Unset variable */
 	PH7_OP_LOADV,        /* Load variable */
 	PH7_OP_LOADC,        /* Load constant */
 	PH7_OP_LOAD_IDX,     /* Load array entry */