diff --git a/src/api/api_datalog.cpp b/src/api/api_datalog.cpp
index 19b488239..8f436bf8a 100644
--- a/src/api/api_datalog.cpp
+++ b/src/api/api_datalog.cpp
@@ -395,8 +395,7 @@ extern "C" {
         Z3_string     s) {
         Z3_TRY;
         LOG_Z3_fixedpoint_from_string(c, d, s);
-        std::string str(s);
-        std::istringstream is(str);
+        std::istringstream is(s);
         RETURN_Z3(Z3_fixedpoint_from_stream(c, d, is));
         Z3_CATCH_RETURN(nullptr);
     }
diff --git a/src/api/api_opt.cpp b/src/api/api_opt.cpp
index ebbe1a3db..5854bdaca 100644
--- a/src/api/api_opt.cpp
+++ b/src/api/api_opt.cpp
@@ -383,8 +383,7 @@ extern "C" {
         Z3_string     s) {
         Z3_TRY;
         //LOG_Z3_optimize_from_string(c, d, s);
-        std::string str(s);
-        std::istringstream is(str);
+        std::istringstream is(s);
         Z3_optimize_from_stream(c, d, is, nullptr);
         Z3_CATCH;
     }
diff --git a/src/api/api_params.cpp b/src/api/api_params.cpp
index 1454525d6..2d0770903 100644
--- a/src/api/api_params.cpp
+++ b/src/api/api_params.cpp
@@ -116,7 +116,7 @@ extern "C" {
         RESET_ERROR_CODE();
         std::ostringstream buffer;
         to_params(p)->m_params.display(buffer);
-        return mk_c(c)->mk_external_string(buffer.str());
+        return mk_c(c)->mk_external_string(std::move(buffer).str());
         Z3_CATCH_RETURN("");
     }
 
@@ -208,7 +208,7 @@ extern "C" {
             buffer << to_param_descrs_ptr(p)->get_param_name(i);
         }
         buffer << ")";
-        return mk_c(c)->mk_external_string(buffer.str());
+        return mk_c(c)->mk_external_string(std::move(buffer).str());
         Z3_CATCH_RETURN("");
     }
 
diff --git a/src/api/api_parsers.cpp b/src/api/api_parsers.cpp
index 00fe1cd8b..2510d5e17 100644
--- a/src/api/api_parsers.cpp
+++ b/src/api/api_parsers.cpp
@@ -157,8 +157,7 @@ extern "C" {
     Z3_ast_vector Z3_API Z3_parser_context_from_string(Z3_context c, Z3_parser_context pc, Z3_string str) {
         Z3_TRY;
         LOG_Z3_parser_context_from_string(c, pc, str);
-        std::string s(str);
-        std::istringstream is(s);
+        std::istringstream is(str);
         auto& ctx = to_parser_context(pc)->ctx;
         Z3_ast_vector r = Z3_parser_context_parse_stream(c, ctx, false, is);
         RETURN_Z3(r);
@@ -202,8 +201,7 @@ extern "C" {
                                           Z3_func_decl const decls[]) {
         Z3_TRY;
         LOG_Z3_parse_smtlib2_string(c, str, num_sorts, sort_names, sorts, num_decls, decl_names, decls);
-        std::string s(str);
-        std::istringstream is(s);
+        std::istringstream is(str);
         Z3_ast_vector r = parse_smtlib2_stream(false, c, is, num_sorts, sort_names, sorts, num_decls, decl_names, decls);
         RETURN_Z3(r);
         Z3_CATCH_RETURN(nullptr);
@@ -243,8 +241,7 @@ extern "C" {
             ctx->set_solver_factory(mk_smt_strategic_solver_factory());
         }
         scoped_ptr<cmd_context>& ctx = mk_c(c)->cmd();
-        std::string s(str);
-        std::istringstream is(s);
+        std::istringstream is(str);
         ctx->set_regular_stream(ous);
         ctx->set_diagnostic_stream(ous);
         cmd_context::scoped_redirect _redirect(*ctx);
diff --git a/src/api/api_solver.cpp b/src/api/api_solver.cpp
index 5edc42157..94d72462f 100644
--- a/src/api/api_solver.cpp
+++ b/src/api/api_solver.cpp
@@ -318,8 +318,7 @@ extern "C" {
     void Z3_API Z3_solver_from_string(Z3_context c, Z3_solver s, Z3_string c_str) {
         Z3_TRY;
         LOG_Z3_solver_from_string(c, s, c_str);
-        std::string str(c_str);
-        std::istringstream is(str);
+        std::istringstream is(c_str);
         if (is_dimacs_string(c_str)) {
             solver_from_dimacs_stream(c, s, is);
         }