THRIFT-6377: Grow a list<bool> with push_back so generated C++ builds as C++11

Client: cpp

std::vector<bool> has no emplace_back() before C++14, so code generated for a
list<bool> field, directly or through a typedef, did not compile as C++11 against
libc++. Other element types keep emplace_back().

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

compiler/cpp/src/thrift/generate/t_cpp_generator.cc

@@ -4544,8 +4544,13 @@ void t_cpp_generator::generate_deserialize_list_element(ostream& out,
   } else {
     // The vector's capacity was reserved (capped) from the declared count, so grow it one element
     // at a time and read into the element just appended, rather than indexing into a full resize.
+    // std::vector<bool> has no emplace_back() before C++14, so a list of bool uses push_back().
     (void)index;
-    indent(out) << prefix << ".emplace_back();" << '\n';
+    if (tlist->get_elem_type()->get_true_type()->is_bool()) {
+      indent(out) << prefix << ".push_back(false);" << '\n';
+    } else {
+      indent(out) << prefix << ".emplace_back();" << '\n';
+    }
     t_field felem(tlist->get_elem_type(), prefix + ".back()");
     generate_deserialize_field(out, &felem);
   }

compiler/cpp/tests/cpp/t_cpp_generator_list_bool_tests.cc

@@ -0,0 +1,59 @@
+// Licensed to the Apache Software Foundation(ASF) under one
+// or more contributor license agreements.See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+// 
+//     http://www.apache.org/licenses/LICENSE-2.0
+// 
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#include "t_cpp_generator_test_utils.h"
+
+using std::string;
+using std::map;
+using cpp_generator_test_utils::read_file;
+using cpp_generator_test_utils::source_dir;
+using cpp_generator_test_utils::join_path;
+using cpp_generator_test_utils::parse_thrift_for_test;
+
+// std::vector<bool> has emplace_back() only from C++14 on, and the generated code has to build as
+// C++11, so a list of bool (directly or through a typedef) must be grown with push_back().
+TEST_CASE("t_cpp_generator grows a list<bool> with push_back, not emplace_back", "[functional]")
+{
+    string path = join_path(source_dir(), "test_list_bool.thrift");
+    string name = "test_list_bool";
+    map<string, string> parsed_options;
+    string option_string = "";
+
+    std::unique_ptr<t_program> program(new t_program(path, name));
+    parse_thrift_for_test(program.get());
+
+    std::unique_ptr<t_generator> gen(
+        t_generator_registry::get_generator(program.get(), "cpp", parsed_options, option_string));
+    REQUIRE(gen != nullptr);
+    REQUIRE_NOTHROW(gen->generate_program());
+
+    string generated = read_file("gen-cpp/test_list_bool_types.cpp");
+    REQUIRE(!generated.empty());
+
+    REQUIRE(generated.find("this->flags.push_back(false);") != string::npos);
+    REQUIRE(generated.find("this->typedef_flags.push_back(false);") != string::npos);
+    REQUIRE(generated.find("this->flags.emplace_back();") == string::npos);
+    REQUIRE(generated.find("this->typedef_flags.emplace_back();") == string::npos);
+
+    // The outer list holds vectors, so it keeps emplace_back(); its elements are lists of bool.
+    REQUIRE(generated.find("this->nested_flags.emplace_back();") != string::npos);
+    REQUIRE(generated.find("this->nested_flags.back().push_back(false);") != string::npos);
+    REQUIRE(generated.find("this->nested_flags.back().emplace_back();") == string::npos);
+
+    // Every other element type is unchanged.
+    REQUIRE(generated.find("this->numbers.emplace_back();") != string::npos);
+}

compiler/cpp/tests/cpp/test_list_bool.thrift

@@ -0,0 +1,29 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+namespace cpp test.list_bool
+
+typedef bool Flag
+
+struct ListBool {
+  1: list<bool> flags;
+  2: list<Flag> typedef_flags;
+  3: list<list<bool>> nested_flags;
+  4: list<i32> numbers;
+}