diff --git a/CMakeLists.txt b/CMakeLists.txt
index 809fc806..30e407da 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -16,8 +16,16 @@ if(CODON_JUPYTER)
 endif()
 
 set(CMAKE_CXX_STANDARD 17)
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fvisibility-inlines-hidden -pedantic -Wno-return-type-c-linkage -Wno-gnu-zero-variadic-macro-arguments")
-set(CMAKE_CXX_FLAGS_DEBUG "-g -fno-limit-debug-info")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -pedantic -fvisibility-inlines-hidden -Wno-return-type-c-linkage -Wno-gnu-zero-variadic-macro-arguments")
+else()
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-return-type")
+endif()
+set(CMAKE_CXX_FLAGS_DEBUG "-g")
+if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+    set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -fno-limit-debug-info")
+endif()
 set(CMAKE_CXX_FLAGS_RELEASE "-O3")
 include_directories(.)
 
diff --git a/codon/app/main.cpp b/codon/app/main.cpp
index ae830ccf..de3da5c9 100644
--- a/codon/app/main.cpp
+++ b/codon/app/main.cpp
@@ -84,10 +84,11 @@ std::unique_ptr<codon::Compiler> processSource(const std::vector<const char *> &
                                                bool standalone) {
   llvm::cl::opt<std::string> input(llvm::cl::Positional, llvm::cl::desc("<input file>"),
                                    llvm::cl::init("-"));
+  auto regs = llvm::cl::getRegisteredOptions();
   llvm::cl::opt<OptMode> optMode(
       llvm::cl::desc("optimization mode"),
       llvm::cl::values(
-          clEnumValN(Debug, "debug",
+          clEnumValN(Debug, regs.find("debug") != regs.end() ? "default" : "debug",
                      "Turn off compiler optimizations and show backtraces"),
           clEnumValN(Release, "release",
                      "Turn on compiler optimizations and disable debug info")),
diff --git a/codon/parser/visitors/simplify/simplify_expr.cpp b/codon/parser/visitors/simplify/simplify_expr.cpp
index ae2bf528..f17bec5a 100644
--- a/codon/parser/visitors/simplify/simplify_expr.cpp
+++ b/codon/parser/visitors/simplify/simplify_expr.cpp
@@ -500,9 +500,9 @@ void SimplifyVisitor::visit(CallExpr *expr) {
       ctx->add(SimplifyItem::Var, varName, varName);
       var = N<IdExpr>(varName);
       ctx->addBlock(); // prevent tmp vars from being toplevel vars
-      ex = N<StmtExpr>(
-          transform(N<AssignStmt>(clone(g->loops[0].vars), clone(var), nullptr, true)),
-          transform(ex));
+      auto head =
+          transform(N<AssignStmt>(clone(g->loops[0].vars), clone(var), nullptr, true));
+      ex = N<StmtExpr>(head, transform(ex));
       ctx->popBlock();
     }
     std::vector<GeneratorBody> body;
diff --git a/codon/parser/visitors/simplify/simplify_stmt.cpp b/codon/parser/visitors/simplify/simplify_stmt.cpp
index d1e420ce..ff09cf15 100644
--- a/codon/parser/visitors/simplify/simplify_stmt.cpp
+++ b/codon/parser/visitors/simplify/simplify_stmt.cpp
@@ -180,7 +180,9 @@ void SimplifyVisitor::visit(WhileStmt *stmt) {
         transform(N<AssignStmt>(N<IdExpr>(breakVar), N<BoolExpr>(true), nullptr, true));
   }
   ctx->loops.push_back(breakVar); // needed for transforming break in loop..else blocks
-  StmtPtr whileStmt = N<WhileStmt>(transform(cond), transform(stmt->suite));
+
+  cond = transform(cond);
+  StmtPtr whileStmt = N<WhileStmt>(cond, transform(stmt->suite));
   ctx->loops.pop_back();
   if (stmt->elseSuite && stmt->elseSuite->firstInBlock()) {
     resultStmt =
@@ -232,7 +234,8 @@ void SimplifyVisitor::visit(ForStmt *stmt) {
   ctx->addBlock();
   if (auto i = stmt->var->getId()) {
     ctx->add(SimplifyItem::Var, i->value, ctx->generateCanonicalName(i->value));
-    forStmt = N<ForStmt>(transform(stmt->var), clone(iter), transform(stmt->suite),
+    auto var = transform(stmt->var);
+    forStmt = N<ForStmt>(var, clone(iter), transform(stmt->suite),
                          nullptr, decorator, ompArgs);
   } else {
     std::string varName = ctx->cache->getTemporaryVar("for");
@@ -259,8 +262,8 @@ void SimplifyVisitor::visit(ForStmt *stmt) {
 
 void SimplifyVisitor::visit(IfStmt *stmt) {
   seqassert(stmt->cond, "invalid if statement");
-  resultStmt = N<IfStmt>(transform(stmt->cond), transform(stmt->ifSuite),
-                         transform(stmt->elseSuite));
+  auto cond = transform(stmt->cond);
+  resultStmt = N<IfStmt>(cond, transform(stmt->ifSuite), transform(stmt->elseSuite));
 }
 
 void SimplifyVisitor::visit(MatchStmt *stmt) {
diff --git a/codon/parser/visitors/translate/translate.cpp b/codon/parser/visitors/translate/translate.cpp
index 33779418..ebeee5bb 100644
--- a/codon/parser/visitors/translate/translate.cpp
+++ b/codon/parser/visitors/translate/translate.cpp
@@ -91,8 +91,10 @@ void TranslateVisitor::visit(IdExpr *expr) {
 }
 
 void TranslateVisitor::visit(IfExpr *expr) {
-  result = make<ir::TernaryInstr>(expr, transform(expr->cond), transform(expr->ifexpr),
-                                  transform(expr->elsexpr));
+  auto cond = transform(expr->cond);
+  auto ifexpr = transform(expr->ifexpr);
+  auto elsexpr = transform(expr->elsexpr);
+  result = make<ir::TernaryInstr>(expr, cond, ifexpr, elsexpr);
 }
 
 void TranslateVisitor::visit(CallExpr *expr) {
diff --git a/codon/parser/visitors/translate/translate_ctx.cpp b/codon/parser/visitors/translate/translate_ctx.cpp
index 690c0b84..7d7589c2 100644
--- a/codon/parser/visitors/translate/translate_ctx.cpp
+++ b/codon/parser/visitors/translate/translate_ctx.cpp
@@ -21,14 +21,14 @@ std::shared_ptr<TranslateItem> TranslateContext::find(const std::string &name) c
     return t;
   std::shared_ptr<TranslateItem> ret = nullptr;
   auto tt = cache->typeCtx->find(name);
-  if (tt->isType() && tt->type->canRealize()) {
+  if (tt && tt->isType() && tt->type->canRealize()) {
     ret = std::make_shared<TranslateItem>(TranslateItem::Type, bases[0]);
     seqassert(in(cache->classes, tt->type->getClass()->name) &&
                   in(cache->classes[tt->type->getClass()->name].realizations, name),
               "cannot find type realization {}", name);
     ret->handle.type =
         cache->classes[tt->type->getClass()->name].realizations[name]->ir;
-  } else if (tt->type->getFunc() && tt->type->canRealize()) {
+  } else if (tt && tt->type->getFunc() && tt->type->canRealize()) {
     ret = std::make_shared<TranslateItem>(TranslateItem::Func, bases[0]);
     seqassert(
         in(cache->functions, tt->type->getFunc()->ast->name) &&
diff --git a/test/parser/simplify_stmt.codon b/test/parser/simplify_stmt.codon
index d849b7dd..28791469 100644
--- a/test/parser/simplify_stmt.codon
+++ b/test/parser/simplify_stmt.codon
@@ -381,6 +381,8 @@ print log(5.5)  #: 1.70475
 #%% import_c_dylib,barebones
 from internal.dlopen import dlext
 RT = "./libcodonrt." + dlext()
+if RT[-3:] == ".so":
+    RT = "build/" + RT[2:]
 from C import RT.seq_str_int(int) -> str as sp
 print sp(65)  #: 65