C语言的强大(C语言实现异常机制)
一直知道C很强大,可以编写操作系统等等,但是一直没有概念
今天看了一下KVM的CLDC1.1的源代码,太酷了,一切都是C,加载class,运行class,类多态实现…..加载JAR,运行JAR….实现线程…..还包括实现了异常机制,好强大!
下载地址: j2megame.cn下载
一切的一切,继续学习…..距离….
虽然看不懂,但记录一下实现的,看代码
global.h (异常的实现)
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/* * There must not be any allocation guard active when entering a TRY block * as an exception throw will always cause at least one allocation (for the * exception object) thus potentially invalidating any pointers being * guarded by the allocation guard. Note however that this does not preclude * using an allocation guard inside a TRY block. */ #define ASSERT_NO_ALLOCATION_GUARD \ if (NoAllocation > 0) { \ fatalError(KVM_MSG_TRY_BLOCK_ENTERED_WHEN_ALLOCATION_FORBIDDEN); \ } #else #define TRACE_EXCEPTION(name) #define ASSERT_NO_ALLOCATION_GUARD #endif #define TRY \ { \ struct throwableScopeStruct __scope__; \ int __state__; \ jmp_buf __env__; \ __scope__.outer = ThrowableScope; \ ThrowableScope = &__scope__; \ ThrowableScope->env = &__env__; \ ThrowableScope->tmpRootsCount = TemporaryRootsLength; \ ASSERT_NO_ALLOCATION_GUARD \ TRACE_EXCEPTION("TRY") \ if ((__state__ = setjmp(__env__)) == 0) { /* * Any non-null THROWABLE_INSTANCE passed into a CATCH clause * is protected as a temporary root. */ #define CATCH(__throwable__) \ } \ TRACE_EXCEPTION("CATCH") \ ThrowableScope = __scope__.outer; \ TemporaryRootsLength = __scope__.tmpRootsCount; \ if (__state__ != 0) { \ START_TEMPORARY_ROOTS \ DECLARE_TEMPORARY_ROOT(THROWABLE_INSTANCE, \ __throwable__,__scope__.throwable); #define END_CATCH \ END_TEMPORARY_ROOTS \ } \ } /* * This macro is required for jumping out of a CATCH block with a goto. * This is used in FastInterpret so that the interpreter loop is re-entered * with a fresh TRY statement. */ #define END_CATCH_AND_GOTO(label) \ END_TEMPORARY_ROOTS \ goto label; \ } \ } #define THROW(__throwable__) \ { \ THROWABLE_INSTANCE __t__ = __throwable__; \ TRACE_EXCEPTION("THROW") \ if (__t__ == NULL) \ fatalVMError("THROW called with NULL"); \ ThrowableScope->throwable = __t__; \ longjmp(*((jmp_buf*)ThrowableScope->env),1); \ } |
class.c (异常的使用)
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/*=========================================== * FUNCTION: initializeClass() * TYPE: constructor * OVERVIEW: After loading a class, it must be initialized * by executing the possible internal static * constructor '<clinit>'. This will initialize the * necessary static structures. * * This function sets up the necessary Class.runClinit * frame and returns to the interpreter. * INTERFACE: * parameters: class pointer * returns: <nothing> *===========================================*/ void initializeClass(INSTANCE_CLASS thisClass) { if (thisClass->status == CLASS_ERROR) { raiseException(NoClassDefFoundError); } else if (thisClass->status < CLASS_READY) { if (thisClass->status < CLASS_VERIFIED) { verifyClass(thisClass); } /* * VerifyError will have been thrown or status will be * CLASS_VERIFIED. We can skip execution of <clinit> altogether if * it does not exists AND the superclass is already initialised. */ if ((thisClass->superClass == NULL || thisClass->superClass->status == CLASS_READY) && getSpecialMethod(thisClass,clinitNameAndType) == NULL) { setClassStatus(thisClass,CLASS_READY); } else { TRY { pushFrame(RunCustomCodeMethod); pushStackAsType(CustomCodeCallbackFunction, &runClinit); pushStackAsType(INSTANCE_CLASS, thisClass); pushStackAsType(long, 1); } CATCH (e) { /* Stack overflow */ setClassStatus(thisClass, CLASS_ERROR); THROW(e); } END_CATCH } } } |
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