Allow using NaN default values

rosidl_generator_c/resource/idl__struct.h.em

@@ -32,6 +32,7 @@ extern "C"
 {
 #endif
 
+#include <math.h>
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>

rosidl_generator_c/rosidl_generator_c/__init__.py

@@ -172,6 +172,17 @@ def value_to_c(type_, value):
 
 
 def basic_value_to_c(type_, value):
+    """
+    Convert a python value into a string representing that value in C.
+
+    Warning: The value has to be a primitive and not a list
+      (aka this function doesn't work for arrays)
+    @param type_: a ROS IDL basic type
+    @type type_: builtin.str
+    @param value: the value to convert
+    @type value: builtin.str
+    @returns: a string containing the C representation of the value
+    """
     assert isinstance(type_, BasicType)
     assert value is not None
 
@@ -209,9 +220,13 @@ def basic_value_to_c(type_, value):
         return f'{value}ull'
 
     if 'float' == type_.typename:
+        if 'nan' == value:
+            return 'NAN'
         return f'{value}f'
 
     if 'double' == type_.typename:
+        if 'nan' == value:
+            return '(double)NAN'
         return f'{value}l'
 
     assert False, "unknown basic type '%s'" % type_

rosidl_generator_cpp/resource/idl__struct.hpp.em

@@ -31,6 +31,7 @@ include_directives = set()
 #include <memory>
 #include <string>
 #include <vector>
+#include <limits>
 
 #include "rosidl_runtime_cpp/bounded_vector.hpp"
 #include "rosidl_runtime_cpp/message_initialization.hpp"

rosidl_generator_cpp/resource/msg__struct.hpp.em

@@ -287,7 +287,17 @@ non_defaulted_zero_initialized_members = [
 u@
 @[    end if]@
 @[   elif constant.type.typename == 'float']@
+@[    if constant.value == 'nan']
+    std::numeric_limits<float>::quiet_NaN()@
+@[    else]@
     @(constant.value)f@
+@[    end if]@
+@[   elif constant.type.typename == 'double']@
+@[    if constant.value == 'nan']
+    std::numeric_limits<double>::quiet_NaN()@
+@[    else]@
+    @(constant.value)f@
+@[    end if]@
 @[   else]@
     @(constant.value)@
 @[   end if];

rosidl_generator_cpp/rosidl_generator_cpp/__init__.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 from ast import literal_eval
+from math import isnan
 
 from rosidl_parser.definition import AbstractGenericString
 from rosidl_parser.definition import AbstractNestedType
@@ -198,13 +199,18 @@ def primitive_value_to_cpp(type_, value):
     if type_.typename in [
         'short', 'unsigned short',
         'char', 'wchar',
-        'double', 'long double',
         'octet',
         'int8', 'uint8',
         'int16', 'uint16',
     ]:
         return str(value)
 
+    if type_.typename in ['double', 'long double']:
+        if isnan(value):
+            return 'std::numeric_limits<double>::quiet_NaN()'
+        else:
+            return str(value)
+
     if type_.typename == 'int32':
         # Handle edge case for INT32_MIN
         # Specifically, MSVC is not happy in this case
@@ -226,6 +232,8 @@ def primitive_value_to_cpp(type_, value):
         return '%sull' % value
 
     if type_.typename == 'float':
+        if isnan(value):
+            return 'std::numeric_limits<float>::quiet_NaN()'
         return '%sf' % value
 
     assert False, "unknown primitive type '%s'" % type_.typename

rosidl_generator_tests/CMakeLists.txt

@@ -36,6 +36,7 @@ if(BUILD_TESTING)
     ${test_interface_files_SRV_FILES}
     msg/BasicIdl.idl
     msg/SmallConstant.msg
+    msg/NanTest.msg
     ADD_LINTER_TESTS
     SKIP_INSTALL
   )

rosidl_generator_tests/msg/NanTest.msg

@@ -0,0 +1,4 @@
+float64 FLOAT64_NAN_UC=NAN
+float64 FLOAT64_NAN_LC=nan
+float32 FLOAT32_NAN_UC=NAN
+float32 FLOAT32_NAN_LC=nan

rosidl_generator_tests/test/rosidl_generator_cpp/test_interfaces.cpp

@@ -41,6 +41,7 @@
 #include "rosidl_generator_tests/msg/multi_nested.hpp"
 #include "rosidl_generator_tests/msg/nested.hpp"
 #include "rosidl_generator_tests/msg/small_constant.hpp"
+#include "rosidl_generator_tests/msg/nan_test.hpp"
 #include "rosidl_generator_tests/msg/strings.hpp"
 #include "rosidl_generator_tests/msg/unbounded_sequences.hpp"
 #include "rosidl_generator_tests/msg/w_strings.hpp"
@@ -542,3 +543,16 @@ TEST(Test_messages, Test_string_array_static) {
     message.string_values_default.begin());
   ASSERT_EQ(pattern_string_values_default, message.string_values_default);
 }
+
+TEST(Test_messages, Test_nan) {
+  float float_nv_uc = rosidl_generator_tests::msg::NanTest::FLOAT32_NAN_UC;
+  float float_nv_lc = rosidl_generator_tests::msg::NanTest::FLOAT32_NAN_UC;
+  double double_nv_uc = rosidl_generator_tests::msg::NanTest::FLOAT64_NAN_UC;
+  double double_nv_lc = rosidl_generator_tests::msg::NanTest::FLOAT64_NAN_UC;
+
+  // nan is not equal to nan, so make sure the values are nan
+  EXPECT_TRUE(std::isnan(float_nv_uc));
+  EXPECT_TRUE(std::isnan(float_nv_lc));
+  EXPECT_TRUE(std::isnan(double_nv_uc));
+  EXPECT_TRUE(std::isnan(double_nv_lc));
+}