From fee5f32f5818a2fd075aa6035de2fa980d2b8a58 Mon Sep 17 00:00:00 2001
From: Adrian Thurston <thurston@complang.org>
Date: Tue, 21 Jan 2014 21:28:27 -0500
Subject: the contiguous instruction also pushes a null value

An initial push prevents a push-pop-push from clearing the contiguous block.
This can happen easily when evaluating args (quals, expresssions, etc).
---
 src/bytecode.c   |  2 ++
 src/iter.c       |  1 +
 src/parsedata.h  |  1 +
 src/synthesis.cc | 24 +++++++++++++++++++++---
 4 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/src/bytecode.c b/src/bytecode.c
index 1065d923..d69cf902 100644
--- a/src/bytecode.c
+++ b/src/bytecode.c
@@ -3343,6 +3343,7 @@ again:
 			read_half( size );
 			debug( prg, REALM_BYTECODE, "IN_CONTIGUOUS %hd\n", size );
 			vm_contiguous( size );
+			vm_push( 0 );
 			break;
 		}
 		case IN_INIT_LOCALS: {
@@ -3644,6 +3645,7 @@ again:
 				instr = (Code*) vm_pop();
 				Tree *retVal = vm_pop();
 				vm_popn( fi->argSize );
+				vm_pop();
 
 				treeDownref( prg, sp, retVal );
 			}
diff --git a/src/iter.c b/src/iter.c
index 3d38fa3a..9e60a2df 100644
--- a/src/iter.c
+++ b/src/iter.c
@@ -165,6 +165,7 @@ void userIterDestroy2( Program *prg, Tree ***psp, UserIter *uiter )
 		vm_popn( uiter->yieldSize );
 		vm_popn( sizeof(UserIter) / sizeof(Word) );
 		vm_popn( argSize );
+		vm_pop();
 
 		uiter->type = 0;
 
diff --git a/src/parsedata.h b/src/parsedata.h
index 85b70b8c..f9f7df2e 100644
--- a/src/parsedata.h
+++ b/src/parsedata.h
@@ -979,6 +979,7 @@ struct Compiler
 
 	bool beginContiguous( CodeVect &code, int stretch );
 	void endContiguous( CodeVect &code, bool resetContiguous );
+	void clearContiguous( CodeVect &code, bool resetContiguous );
 
 	void declareReVars();
 };
diff --git a/src/synthesis.cc b/src/synthesis.cc
index 4286320b..ac77b4b0 100644
--- a/src/synthesis.cc
+++ b/src/synthesis.cc
@@ -899,7 +899,9 @@ bool Compiler::beginContiguous( CodeVect &code, int stretch )
 	if ( inContiguous )
 		contiguousStretch += stretch;
 	else {
-		contiguousStretch = stretch;
+		/* We add one for the push that always comes with the contiguous
+		 * statement. */
+		contiguousStretch = stretch + 1;
 
 		code.append( IN_CONTIGUOUS );
 		contiguousOffset = code.length();
@@ -920,6 +922,14 @@ void Compiler::endContiguous( CodeVect &code, bool resetContiguous )
 	}
 }
 
+void Compiler::clearContiguous( CodeVect &code, bool resetContiguous )
+{
+	if ( resetContiguous ) {
+		code.append( IN_TOP_SWAP );
+		code.append( IN_POP );
+	}
+}
+
 UniqueType *LangVarRef::evaluateCall( Compiler *pd, CodeVect &code, CallArgVect *args ) 
 {
 	/* Evaluate the object. */
@@ -944,6 +954,7 @@ UniqueType *LangVarRef::evaluateCall( Compiler *pd, CodeVect &code, CallArgVect
 	delete[] paramRefs;
 
 	pd->endContiguous( code, resetContiguous );
+	pd->clearContiguous( code, resetContiguous );
 
 	/* Return the type to the expression. */
 	return lookup.uniqueType;
@@ -1354,6 +1365,7 @@ void LangTerm::evaluateSendStream( Compiler *pd, CodeVect &code ) const
 	 * leave the varref on the stack. */
 
 	pd->endContiguous( code, resetContiguous );
+	pd->clearContiguous( code, resetContiguous );
 }
 
 void LangTerm::evaluateSendParser( Compiler *pd, CodeVect &code ) const
@@ -1873,6 +1885,7 @@ UniqueType *LangTerm::evaluateMakeToken( Compiler *pd, CodeVect &code ) const
 	code.append( args->length() );
 
 	pd->endContiguous( code, resetContiguous );
+	pd->clearContiguous( code, resetContiguous );
 
 	return pd->uniqueTypeAny;
 }
@@ -1903,6 +1916,7 @@ UniqueType *LangTerm::evaluateMakeTree( Compiler *pd, CodeVect &code ) const
 	code.append( args->length() );
 
 	pd->endContiguous( code, resetContiguous );
+	pd->clearContiguous( code, resetContiguous );
 
 	return pd->uniqueTypeAny;
 }
@@ -2002,6 +2016,8 @@ void LangStmt::compileForIter( Compiler *pd, CodeVect &code ) const
 	ObjectField **paramRefs = iterCall->langTerm->varRef->evaluateArgs(
 			pd, code, lookup, iterCall->langTerm->args );
 
+	pd->endContiguous( code, resetContiguous );
+
 	if ( pd->revertOn )
 		code.append( iterUT->iterDef->inCreateWV );
 	else
@@ -2018,14 +2034,16 @@ void LangStmt::compileForIter( Compiler *pd, CodeVect &code ) const
 			code.appendHalf( searchUT->langEl->id );
 	}
 
-	pd->endContiguous( code, resetContiguous );
-
 	compileForIterBody( pd, code, iterUT );
 
+
 	iterCall->langTerm->varRef->popRefQuals( pd, code, lookup, iterCall->langTerm->args );
 
 	iterCall->langTerm->varRef->resetActiveRefs( pd, lookup, paramRefs );
 	delete[] paramRefs;
+
+	if ( resetContiguous )
+		code.append( IN_POP );
 }
 
 void LangStmt::compileWhile( Compiler *pd, CodeVect &code ) const
-- 
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