[Mono-dev] increased memory usage when embedding mono under special environment

Jovic, Vladimir vladimir.jovic at ifm.com
Tue Jul 4 12:39:35 UTC 2017


I am crosscompiling mono 4.4.2 for PPC platform (couldn't compile newer version, as the configuration fails).
Also, I implemented a c++ library, which executes a C# function in DLL. This library is dynamically loaded at runtime (using dlopen) by a program with very special environment. I wouldn't be surprised to hear that this program experience both stack smash and memory overwrites at the same time, but I am not in a position to pick.

Now the problem I am having is: when I use my library in a standalone program, then it works fine. But when I use my library with the program with this special environment, than it uses 40 more megabytes to do some initializations. The parameters for both programs are the same (default, as I do not set any environment variables).

The code to set the mono library is next. As you see, it is a code that can be found in any example of how to execute a c# function from a DLL.

MonoMethod* csMethodEntryPoint = NULL;

void SetMethodEntryPoint( const std::string& ifmDllsPath )
    mono_config_parse( NULL );

    MonoDomain* monoDomain = mono_jit_init_version( "pdm_mono_sdk", "v4.0.30319" );

    const std::string assemblyName( ifmDllsPath + "/ifmApiLinuxWrapper.dll" );
    MonoAssembly* assembly = mono_domain_assembly_open( monoDomain, assemblyName.c_str() );
    if ( NULL == assembly )
        throw std::runtime_error( "assembly is NULL" );

    MonoImage* monoImage = mono_assembly_get_image( assembly );
    if ( NULL == monoImage )
        throw std::runtime_error( "monoImage is NULL" );

    MonoClass* entityClass = mono_class_from_name( monoImage, "ifmApiLinuxWrapper", "ifmApiLinuxWrapper" );
    if ( NULL ==  entityClass )
        throw std::runtime_error( "entityClass is NULL" );

    csMethodEntryPoint = mono_class_get_method_from_name( entityClass, "ApiCmdRequest", 2 );
    if ( NULL == csMethodEntryPoint )
        throw std::runtime_error( "entryPoint is NULL" );

The function that allocates extra memory is mono_jit_init_version(). In a standalone program, it allocates 1M, and with this special program 20M!
I said above that I lose 40M. So, 19M with mono_jit_init_version(), and extra 21M from a call to c# function.
I took a look into the mono source code for mono_jit_init_version() function, but the function is so huge, that I got lost quite quickly.

The question is how to debug this. Can I set some environment variable to help me track why extra memory is allocated?

Vladimir Jovic

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