code.cs

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Threading;
using System.Threading.Tasks;

namespace TestStacktrace
{
	[AttributeUsage(AttributeTargets.Class, AllowMultiple = true)]
	public class CAttribute : Attribute
	{
		public string FieldName;
		public Type FieldType;

		public string PropName { get; set; }
		public Type PropType { get; set; }
	}

	[CAttribute(FieldName = "a", FieldType = typeof(CClass), PropName = "b", PropType = typeof(CAttribute))]
	class CClass
	{

	}

	static class MainClass
	{
		static public void Main(string[] args)
		{
      for (int i = 0; i < 10; ++i)
			{
				typeof(CClass).GetCustomAttributes(typeof(CAttribute), true);
			}
			Console.ReadKey();
		}
	}
}

leaks

Process:         mono-sgen64 [9924]
Path:            /Library/Frameworks/Mono.framework/Versions/5.18.1/bin/mono-sgen64
Load Address:    0x10767d000
Identifier:      mono-sgen64
Version:         ???
Code Type:       X86-64
Parent Process:  zsh [7083]

Date/Time:       2019-05-21 01:42:53.471 +0300
Launch Time:     2019-05-21 01:42:42.008 +0300
OS Version:      Mac OS X 10.14.4 (18E226)
Report Version:  7
Analysis Tool:   /usr/bin/leaks

Physical footprint:         16.1M
Physical footprint (peak):  16.2M
----

leaks Report Version: 4.0, multi-line stacks
leaks[9990]: Process 9924 is not debuggable.
Due to security restrictions, leaks cannot show memory contents of restricted processes.

Process 9924: 9548 nodes malloced for 2048 KB
Process 9924: 32 leaks for 848 total leaked bytes.

STACK OF 26 INSTANCES OF 'ROOT LEAK: malloc<16>':
[thread 0x10922b5c0]:
15  libdyld.dylib                      0x7fff5f9ae3d5 start + 1
14  mono                                  0x10767fd38 main + 264  main.c:405
13  mono                                  0x1076fb0df mono_main + 11615  driver.g.c:2484
12  mono                                  0x1076f7efd mono_jit_exec + 349  driver.g.c:1236
11  mono                                  0x107892eac do_exec_main_checked + 156  object.c:4950
10  mono                                  0x10788f3d4 do_runtime_invoke + 84  object.c:2960
9   mono                                  0x107690f13 mono_jit_runtime_invoke + 1619  mini-runtime.c:3148
  8   ???                                   0x107ea90d9 (wrapper runtime-invoke) <Module>:runtime_invoke_void_object + 9223372041282556122
7   mscorlib.dll.dylib                    0x109b9c728 System_MonoCustomAttrs_GetCustomAttributesBase_System_Reflection_ICustomAttributeProvider_System_Type_bool + 88
6   ???                                   0x107ea928a (wrapper managed-to-native) System.MonoCustomAttrs:GetCustomAttributesInternal + 9223372041282556555
5   mono                                  0x1078f4df7 mono_reflection_get_custom_attrs_by_type_handle + 87  handle.h:649
4   mono                                  0x1078f2e99 mono_custom_attrs_construct_by_type + 489  custom-attrs.c:988
3   mono                                  0x1078f4304 create_custom_attr + 1636  custom-attrs.c:916
2   mono                                  0x107983076 monoeg_malloc + 22  gmem.c:116
1   libsystem_malloc.dylib             0x7fff5fb58b81 malloc + 24
0   libsystem_malloc.dylib             0x7fff5fb58c29 malloc_zone_malloc + 139
====
    26 (416 bytes) << TOTAL >>
      1 (16 bytes) ROOT LEAK: 0x7f88bc80c670 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e120 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e130 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e360 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e370 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e380 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e390 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e3a0 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e3b0 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e3c0 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e3f0 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e400 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e490 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e520 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e530 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e540 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e550 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e560 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e570 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e740 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e750 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e760 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e770 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e780 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e790 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc80e7a0 [16]

STACK OF 3 INSTANCES OF 'ROOT LEAK: malloc<16>':
[thread 0x10922b5c0]:
15  libdyld.dylib                      0x7fff5f9ae3d5 start + 1
14  mono                                  0x10767fd38 main + 264  main.c:405
13  mono                                  0x1076fb0df mono_main + 11615  driver.g.c:2484
12  mono                                  0x1076f7efd mono_jit_exec + 349  driver.g.c:1236
11  mono                                  0x107892eac do_exec_main_checked + 156  object.c:4950
10  mono                                  0x10788f3d4 do_runtime_invoke + 84  object.c:2960
9   mono                                  0x107690f13 mono_jit_runtime_invoke + 1619  mini-runtime.c:3148
8   ???                                   0x107ea90d9 0x7fffffffffffffff + 9223372041282556122
7   mscorlib.dll.dylib                    0x109b9c728 System_MonoCustomAttrs_GetCustomAttributesBase_System_Reflection_ICustomAttributeProvider_System_Type_bool + 88
6   ???                                   0x107ea928a 0x7fffffffffffffff + 9223372041282556555
5   mono                                  0x1078f4df7 mono_reflection_get_custom_attrs_by_type_handle + 87  handle.h:649
4   mono                                  0x1078f2e99 mono_custom_attrs_construct_by_type + 489  custom-attrs.c:988
3   mono                                  0x1078f4304 create_custom_attr + 1636  custom-attrs.c:916
2   mono                                  0x107983076 monoeg_malloc + 22  gmem.c:116
1   libsystem_malloc.dylib             0x7fff5fb58b81 malloc + 24
0   libsystem_malloc.dylib             0x7fff5fb58c29 malloc_zone_malloc + 139
====
    3 (48 bytes) << TOTAL >>
      1 (16 bytes) ROOT LEAK: 0x7f88bc803f50 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc805400 [16]
      1 (16 bytes) ROOT LEAK: 0x7f88bc805590 [16]