diff --git a/src/script_opt/CPP/Types.cc b/src/script_opt/CPP/Types.cc
index b6eaeb2564..64e1e4ed24 100644
--- a/src/script_opt/CPP/Types.cc
+++ b/src/script_opt/CPP/Types.cc
@@ -133,7 +133,7 @@ void CPPCompile::ExpandTypeVar(const TypePtr& t)
 	}
 
 	auto& script_type_name = t->GetName();
-	if ( script_type_name.size() > 0 )
+	if ( ! script_type_name.empty() )
 		AddInit(t, "register_type__CPP(" + tn + ", \"" +
 		           script_type_name + "\");");
 
@@ -181,7 +181,7 @@ void CPPCompile::ExpandEnumTypeVar(const TypePtr& t, string& tn)
 	auto names = et->Names();
 
 	AddInit(t, "{ auto et = " + e_name + ";");
-	AddInit(t, "if ( et->Names().size() == 0 ) {");
+	AddInit(t, "if ( et->Names().empty() ) {");
 
 	for ( const auto& name_pair : et->Names() )
 		AddInit(t, string("\tet->AddNameInternal(\"") +
diff --git a/src/script_opt/CPP/Vars.cc b/src/script_opt/CPP/Vars.cc
index 6e1795123b..76a93ed064 100644
--- a/src/script_opt/CPP/Vars.cc
+++ b/src/script_opt/CPP/Vars.cc
@@ -54,7 +54,7 @@ bool CPPCompile::CheckForCollisions()
 		// the name either (1) wasn't previously used, or (2) if it
 		// was, it was likewise for an enum or a record.
 		const auto& tn = t->GetName();
-		if ( tn.size() == 0 || ! hm.HasGlobal(tn) )
+		if ( tn.empty() || ! hm.HasGlobal(tn) )
 			// No concern of collision since the type name
 			// wasn't previously compiled.
 			continue;
diff --git a/src/script_opt/GenIDDefs.cc b/src/script_opt/GenIDDefs.cc
index 842a65dd36..36137ffdcc 100644
--- a/src/script_opt/GenIDDefs.cc
+++ b/src/script_opt/GenIDDefs.cc
@@ -518,7 +518,7 @@ void GenIDDefs::TrackID(const ID* id, const ExprPtr& e)
 	{
 	auto oi = id->GetOptInfo();
 
-	ASSERT(barrier_blocks.size() > 0);
+	ASSERT(! barrier_blocks.empty());
 	oi->DefinedAfter(curr_stmt, e,
 	                 confluence_blocks, barrier_blocks.back());
 
@@ -529,7 +529,7 @@ void GenIDDefs::TrackID(const ID* id, const ExprPtr& e)
 		// block.
 		modified_IDs[i+1].insert(id);
 
-	if ( confluence_blocks.size() == 0 )
+	if ( confluence_blocks.empty() )
 		// This is a definition at the outermost level.
 		modified_IDs[0].insert(id);
 	}
diff --git a/src/script_opt/GenRDs.cc b/src/script_opt/GenRDs.cc
index 8c59ce4a4d..198fbdc447 100644
--- a/src/script_opt/GenRDs.cc
+++ b/src/script_opt/GenRDs.cc
@@ -357,7 +357,7 @@ void RD_Decorate::TraverseSwitch(const SwitchStmt* sw)
 		bd->Clear();
 		body->Traverse(this);
 
-		if ( bd->PreRDs().size() > 0 )
+		if ( ! bd->PreRDs().empty() )
 			reporter->InternalError("mispropagation of switch body defs");
 
 		if ( body->NoFlowAfter(true) )
@@ -544,7 +544,7 @@ TraversalCode RD_Decorate::PostStmt(const Stmt* s)
 		break;
 
 	case STMT_BREAK:
-		if ( block_defs.size() == 0 )
+		if ( block_defs.empty() )
 			{
 			if ( func_flavor == FUNC_FLAVOR_HOOK )
 				// Treat as a return.
diff --git a/src/script_opt/IDOptInfo.cc b/src/script_opt/IDOptInfo.cc
index a9c1e5d0fd..7670de5aa2 100644
--- a/src/script_opt/IDOptInfo.cc
+++ b/src/script_opt/IDOptInfo.cc
@@ -78,7 +78,7 @@ void IDOptInfo::DefinedAfter(const Stmt* s, const ExprPtr& e,
 
 	if ( ! s )
 		{ // This is a definition-upon-entry
-		ASSERT(usage_regions.size() == 0);
+		ASSERT(usage_regions.empty());
 		usage_regions.emplace_back(0, 0, true, 0);
 		if ( tracing )
 			DumpBlocks();
@@ -88,12 +88,12 @@ void IDOptInfo::DefinedAfter(const Stmt* s, const ExprPtr& e,
 	auto s_oi = s->GetOptInfo();
 	auto stmt_num = s_oi->stmt_num;
 
-	if ( usage_regions.size() == 0 )
+	if ( usage_regions.empty() )
 		{
 		// We're seeing this identifier for the first time,
 		// so we don't have any context or confluence
 		// information for it.  Create its "backstory" region.
-		ASSERT(confluence_stmts.size() == 0);
+		ASSERT(confluence_stmts.empty());
 		usage_regions.emplace_back(0, 0, false, NO_DEF);
 		}
 
@@ -300,7 +300,7 @@ void IDOptInfo::ConfluenceBlockEndsAfter(const Stmt* s, bool no_orig_flow)
 	{
 	auto stmt_num = s->GetOptInfo()->stmt_num;
 
-	ASSERT(confluence_stmts.size() > 0);
+	ASSERT(! confluence_stmts.empty());
 	auto cs = confluence_stmts.back();
 	auto& pc = pending_confluences[cs];
 
@@ -434,7 +434,7 @@ ExprPtr IDOptInfo::DefExprBefore(const Stmt* s)
 
 bool IDOptInfo::IsPossiblyDefinedBefore(int stmt_num)
 	{
-	if ( usage_regions.size() == 0 )
+	if ( usage_regions.empty() )
 		return false;
 
 	return FindRegionBefore(stmt_num).MaybeDefined();
@@ -442,7 +442,7 @@ bool IDOptInfo::IsPossiblyDefinedBefore(int stmt_num)
 
 bool IDOptInfo::IsDefinedBefore(int stmt_num)
 	{
-	if ( usage_regions.size() == 0 )
+	if ( usage_regions.empty() )
 		return false;
 
 	return FindRegionBefore(stmt_num).DefinedAfter() != NO_DEF;
@@ -450,7 +450,7 @@ bool IDOptInfo::IsDefinedBefore(int stmt_num)
 
 int IDOptInfo::DefinitionBefore(int stmt_num)
 	{
-	if ( usage_regions.size() == 0 )
+	if ( usage_regions.empty() )
 		return NO_DEF;
 
 	return FindRegionBefore(stmt_num).DefinedAfter();
@@ -458,7 +458,7 @@ int IDOptInfo::DefinitionBefore(int stmt_num)
 
 ExprPtr IDOptInfo::DefExprBefore(int stmt_num)
 	{
-	if ( usage_regions.size() == 0 )
+	if ( usage_regions.empty() )
 		return nullptr;
 
 	return FindRegionBefore(stmt_num).DefExprAfter();
diff --git a/src/script_opt/UseDefs.cc b/src/script_opt/UseDefs.cc
index a30b8cca3b..9b4093af26 100644
--- a/src/script_opt/UseDefs.cc
+++ b/src/script_opt/UseDefs.cc
@@ -94,7 +94,7 @@ bool UseDefs::RemoveUnused(int iter)
 				     ! CheckIfUnused(s, id.get(), false) )
 					used_ids.emplace_back(id);
 
-			if ( used_ids.size() == 0 )
+			if ( used_ids.empty() )
 				{ // There aren't any ID's to keep.
 				rc->AddStmtToOmit(s);
 				continue;
diff --git a/src/script_opt/ZAM/AM-Opt.cc b/src/script_opt/ZAM/AM-Opt.cc
index 6d165a0d2e..a2bd07ead7 100644
--- a/src/script_opt/ZAM/AM-Opt.cc
+++ b/src/script_opt/ZAM/AM-Opt.cc
@@ -150,7 +150,7 @@ void ZAMCompiler::TallySwitchTargets(const CaseMapsI<T>& switches)
 
 bool ZAMCompiler::RemoveDeadCode()
 	{
-	if ( insts1.size() == 0 )
+	if ( insts1.empty() )
 		return false;
 
 	bool did_removal = false;
diff --git a/src/script_opt/ZAM/Branches.cc b/src/script_opt/ZAM/Branches.cc
index 090ab4ade8..36e44e44b3 100644
--- a/src/script_opt/ZAM/Branches.cc
+++ b/src/script_opt/ZAM/Branches.cc
@@ -99,7 +99,7 @@ void ZAMCompiler::ConcretizeBranch(ZInstI* inst, ZInstI* target,
 
 	if ( target == pending_inst )
 		{
-		if ( insts2.size() == 0 )
+		if ( insts2.empty() )
 			// We're doing this in the context of concretizing
 			// intermediary instructions for dumping them out.
 			t = insts1.size();
diff --git a/src/script_opt/ZAM/Gen-ZAM.cc b/src/script_opt/ZAM/Gen-ZAM.cc
index 2f50cb71b1..08823a22d6 100644
--- a/src/script_opt/ZAM/Gen-ZAM.cc
+++ b/src/script_opt/ZAM/Gen-ZAM.cc
@@ -188,12 +188,12 @@ void ArgsManager::Differentiate()
 
 	for ( auto& arg : args )
 		{
-		if ( full_decl.size() > 0 )
+		if ( ! full_decl.empty() )
 			full_decl += ", ";
 
 		full_decl += arg.decl_type + " " + arg.decl_name;
 
-		if ( full_params.size() > 0 )
+		if ( ! full_params.empty() )
 			full_params += ", ";
 
 		full_params += arg.param_name;
@@ -238,7 +238,7 @@ void ZAM_OpTemplate::Build()
 			break;
 
 		auto words = g->SplitIntoWords(line);
-		if ( words.size() == 0 )
+		if ( words.empty() )
 			break;
 
 		Parse(words[0], line, words);
@@ -384,7 +384,7 @@ void ZAM_OpTemplate::Parse(const string& attr, const string& line,
 		AddEval(g->SkipWords(line, 1));
 
 		auto addl = GatherEval();
-		if ( addl.size() > 0 )
+		if ( ! addl.empty() )
 			AddEval(addl);
 		}
 
@@ -543,7 +543,7 @@ void ZAM_OpTemplate::InstantiateMethodCore(const vector<ZAM_OperandType>& ot,
 		return;
 		}
 
-	assert(ot.size() > 0);
+	assert(! ot.empty());
 
 	string full_suffix = "_" + OpSuffix(ot) + suffix;
 
@@ -673,7 +673,7 @@ void ZAM_OpTemplate::GenAssignOpCore(const vector<ZAM_OperandType>& ot,
 		return;
 		}
 
-	if ( eval.size() != 0)
+	if ( ! eval.empty() )
 		g->Gripe("assign-op should not have an \"eval\"", eval);
 
 	auto lhs_field = (ot[0] == ZAM_OT_ASSIGN_FIELD);
@@ -1284,7 +1284,7 @@ string EvalInstance::OpMarker() const
 void ZAM_ExprOpTemplate::InstantiateEval(const vector<ZAM_OperandType>& ot_orig,
                                          const string& suffix, ZAM_InstClass zc)
 	{
-	if ( expr_types.size() == 0 )
+	if ( expr_types.empty() )
 		{ // No operand types to expand over.
 		ZAM_OpTemplate::InstantiateEval(ot_orig, suffix, zc);
 		return;
@@ -1775,7 +1775,7 @@ void ZAM_InternalBinaryOpTemplate::InstantiateEval(const vector<ZAM_OperandType>
 	auto eval = prelude + GetEval();
 
 	auto& ets = ExprTypes();
-	if ( ets.size() > 0 )
+	if ( ! ets.empty() )
 		{
 		if ( ets.size() != 1 )
 			g->Gripe("internal-binary-op's can have at most one op-type", op_loc);
@@ -1882,7 +1882,7 @@ void ZAM_InternalOpTemplate::Parse(const string& attr, const string& line,
 
 bool TemplateInput::ScanLine(string& line)
 	{
-	if ( put_back.size() > 0 )
+	if ( ! put_back.empty() )
 		{
 		line = put_back;
 		put_back.clear();
diff --git a/src/script_opt/ZAM/Low-Level.cc b/src/script_opt/ZAM/Low-Level.cc
index 3b8e177809..51265a4656 100644
--- a/src/script_opt/ZAM/Low-Level.cc
+++ b/src/script_opt/ZAM/Low-Level.cc
@@ -23,7 +23,7 @@ const ZAMStmt ZAMCompiler::FinishBlock(const ZAMStmt /* start */)
 bool ZAMCompiler::NullStmtOK() const
 	{
 	// They're okay iff they're the entire statement body.
-	return insts1.size() == 0;
+	return insts1.empty();
 	}
 
 const ZAMStmt ZAMCompiler::EmptyStmt()
diff --git a/src/script_opt/ZAM/Stmt.cc b/src/script_opt/ZAM/Stmt.cc
index f49b84cdeb..21f670d2e6 100644
--- a/src/script_opt/ZAM/Stmt.cc
+++ b/src/script_opt/ZAM/Stmt.cc
@@ -959,7 +959,7 @@ const ZAMStmt ZAMCompiler::CompileReturn(const ReturnStmt* r)
 	{
 	auto e = r->StmtExpr();
 
-	if ( retvars.size() == 0 )
+	if ( retvars.empty() )
 		{ // a "true" return
 		if ( e )
 			{
diff --git a/src/script_opt/ZAM/ZBody.cc b/src/script_opt/ZAM/ZBody.cc
index af1e16ba00..dc24aefb8e 100644
--- a/src/script_opt/ZAM/ZBody.cc
+++ b/src/script_opt/ZAM/ZBody.cc
@@ -273,7 +273,7 @@ ValPtr ZBody::DoExec(Frame* f, int start_pc, StmtFlowType& flow)
 		for ( auto s : managed_slots )
 			frame[s].ClearManagedVal();
 
-		if ( table_iters.size() > 0 )
+		if ( ! table_iters.empty() )
 			{
 			local_table_iters =
 			    std::make_unique<TableIterVec>(table_iters.size());
@@ -363,7 +363,7 @@ ValPtr ZBody::DoExec(Frame* f, int start_pc, StmtFlowType& flow)
 
 void ZBody::ProfileExecution() const
 	{
-	if ( inst_count->size() == 0 )
+	if ( inst_count->empty() )
 		{
 		printf("%s has an empty body\n", func_name);
 		return;
@@ -426,12 +426,12 @@ void ZBody::Dump() const
 
 		printf("frame[%d] =", i);
 
-		if ( d.names.size() > 0 )
-			for ( auto& n : d.names )
-				printf(" %s", n);
-		else
+		if ( d.names.empty() )
 			for ( auto& id : d.ids )
 				printf(" %s", id->Name());
+		else
+			for ( auto& n : d.names )
+				printf(" %s", n);
 		printf("\n");
 		}
 
diff --git a/src/script_opt/ZAM/ZInst.cc b/src/script_opt/ZAM/ZInst.cc
index 77ef429c22..7040510d5c 100644
--- a/src/script_opt/ZAM/ZInst.cc
+++ b/src/script_opt/ZAM/ZInst.cc
@@ -231,7 +231,7 @@ string ZInst::VName(int n, int inst_num, const FrameReMap* mappings) const
 		ASSERT(i > 0);
 		}
 
-	auto id = map.names.size() > 0 ? map.names[i-1] : map.ids[i-1]->Name();
+	auto id = map.names.empty() ? map.ids[i-1]->Name() : map.names[i-1];
 
 	return util::fmt("%d (%s)", slot, id);
 	}
@@ -586,7 +586,7 @@ bool ZInstI::IsGlobalLoad() const
 
 	static std::unordered_set<ZOp> global_ops;
 
-	if ( global_ops.size() == 0 )
+	if ( global_ops.empty() )
 		{ // Initialize the set.
 		for ( int t = 0; t < NUM_TYPES; ++t )
 			{