MkKernel_Setup_libmkkernel_C_API

MkKernel PACKAGE - Setup und Cleanup the jvmkkernel … More...

Collaboration diagram for MkKernel_Setup_libmkkernel_C_API:

Functions
void	MkSetup (void)
	setup jvmkkernel internal memory …
void	MkCleanup (void)
	cleanup jvmkkernel internal memory …
bool	MkHasThread (void)
bool	MkHasFork (void)

Variables
bool	MkCleanupActive
	signal that code was triggert by MkCleanup

Detailed Description

MkKernel PACKAGE - Setup und Cleanup the jvmkkernel …

Initializing a jvmkkernel library depends on the Target-Programming-Language (TPL) and the specific nature of the Programming-Language-Micro-Kernel (PLMK).

In general it is required to call a Setup style funtion as FIRST command because of:

• In a static build the shared library constructor/destructor is NOT called
• In a shared build the order of library loading is target-language-specific
• Every executable who uses a meta-code-library (META-LIBRARY) (MkKernel, MqMsgque, LcConfig, ...) which provide a language-specific-type (always assume this) and also support static-build (no constructor is called like C, C++, ...) require a call to the meta-library-setup-function for type-initialization at startup.

If more than one META library is called only the toplevel Setup is required:

• example: The MkKernelSetup is not required if MqMsgqueSetup or LcConfigSetup is already used.

shared library detail

A new jvmkkernel library is initialized with Setup and released again with Cleanup. Both functions are automatically called upon loading and unloading of the shared library.

Example: Definition (C) of the jvmkkernel library startup functions

MK_EXTERN void MK_DECL MkSetup (void) __attribute__ ((constructor(200)));
MK_EXTERN void MK_DECL MkCleanup (void) __attribute__ ((destructor(200)));

In the Programming-Language-Micro-Kernel (PLMK), a type is defined for each thread, which means that the new jvmkkernel library must be known when the thread starts. This is not a problem as long as the external jvmkkernel library is linked to the application. However, if dlopen is used to load the jvmkkernel library, the current restriction is that the new data type from the jvmkkernel library has not been defined in all existing threads.

The point in time when a library is loaded depends heavily on the programming language used.

• A linked language such as C or C++ usually has all libraries initialised at startup.
• A compiled language such as Java and C# only load a library when a function of the library is used and not when the library is declared.
• A scripting language such as Tcl normally loads the library as soon as the declaration (package require myLib) is made, which happens fairly close to the start of the program but is not guaranteed.

‍To avoid all the problems call the Setup directly at the start of the main program.

Example: Start of the LcConfigServer application from the example/cs directory

• The problem with the LcConfigServer application is that the libmkkernel and libmqmsgque libraries are loaded very early, at startup, and the liblcconfig very late, only on request.

static void Main(string[] argv) {
 
  LcConfig.Setup();
 
  var srv = MqFactoryCT<LcConfigServer>.Add().New();
 
  try {
    srv.LinkCreate(argv);
    srv.ProcessEvent(MqWaitOnEventE.FOREVER);
  } catch (Exception e) {
    srv.ErrorCatch(e);
  }
  srv.Exit();
}

Function Documentation

MkCleanup()

void MkCleanup

(

void

)

cleanup jvmkkernel internal memory …

/

/noop [MkCleanup] Cleanup will only be recognized once and will be ignored if not called in the same thread as Setup. After a call to Setup the call to MkCleanup is possible again.

1. By default, the public Cleanup with the gcc: __attribute__ ((cleanup(XXX))) is called when unloading the library.
2. The public Cleanup is only a placeholder and should not be used, the internal Cleanup is always called, even if the public Cleanup is not called.

Note

during cleanup objects will be deleted too -> the language interpreter have to be active /noop [MkCleanup]

MkHasFork()

bool MkHasFork

(

void

)

MkHasThread()

bool MkHasThread

(

void

)

MkSetup()

void MkSetup

(

void

)

setup jvmkkernel internal memory …

Setup will only be recognized once, additional call's will be ignored until a Cleanup is called.

1. By default, the public Setup with the gcc: __attribute__ ((constructor(XXX))) is called when loading the library.
2. If the Target-Programming-Language (TPL) supports late loading of a shared library with dlopen and additionally uses threads, a manual call to Setup very early at startup is required to enforce the correct order of type declarations.

Variable Documentation

MkCleanupActive

bool MkCleanupActive

extern

signal that code was triggert by MkCleanup