I write the code like the following,
// Note that the output object below functions like the C++'s cout. It's my own // implementation of displaying program information and it's insignificant here. try{ try{ //output<<"exhausting the heap"<<endl; int* p = new int(); while(p!=NULL){ p = new int(); } //output<<" heap exhausted"<<endl; } catch(...){ // never reaches here because I use the --force_new_nothrow // Even if I dont't use --force_new_nothrow, the program never // reaches here too... //output<<"heap exhausted. and received an exception"<<endl; } //output<<"now I throw an int"<<endl; throw int(); } catch(...){ // unfortunately, the program never reach here // I guess it's because the exception object is to be created on the heep // but the heap is already exhausted. // So how should I handle the exception when allocation fails occurs? // output some debug imformation //output<<"unkown exception"<<endl; } // never reaches here too... //output<<"end"<<endl; while(1);
Actually the originan code I wrote is more complated. The Exception obj I throw is a class, so is the allocation object type I use to exhaust the heap. I output the address of these object, under the conditions of exhausted heap and unexhausted respectively. I found there is an exception object created on the heap.
So could anyone tell me how to handle the exception when memory allocation fails occurs ?
Sorry, the trailing > is not part of the URL. (Surrounding URLs with <> is how I was taught to write them -- apparently it confuses this fourm software. I'll try to modify my behaviour in the furture.)
any trailing punctuation on a URL confuses this forum software!
But it's not just this forum software; lots of forums which attempt to automatically detect URLs make this type of mistake - the safe rule is to always ensure that there is clear whitespace around a URL.
Thanks to scott, I include these code, the behavior becomes desirable.
// To initialize the exceptions system before main is entered, // we have to include the following function in the link. // __ARM_exceptions_init will be called before main and // init of any global variables extern "C" void __cxa_get_globals(void); extern "C" void __ARM_exceptions_init(void) { output<<"__ARM_exceptions_init()"<<endl; __cxa_get_globals(); } // this function is never called. To make __ARM_exceptions_buffer_init called, // we must include the symbol __ARM_exceptions_buffer_required extern "C" void __ARM_exceptions_buffer_required(){ output<<"__ARM_exceptions_buffer_required()"<<endl; return ; } //static int buf[20]; // simple re-definition, not necessary. I worte it just to trace the call of // functions // extern "C" void *__ARM_exceptions_buffer_init(){ // output<<"__ARM_exceptions_buffer_init()"<<endl; // return buf; // just to test the behavior // } // extern "C" void *__ARM_exceptions_buffer_allocate(void *buffer, size_t size){ // output<<"__ARM_exceptions_buffer_allocate()"<<endl; // // just to test the behavior when heap is exhausted // // no complicated management is required here! // return buf; // } // extern "C" void *__ARM_exceptions_buffer_free(void *buffer, void *addr){ // output<<"__ARM_exceptions_buffer_free()"<<endl; // return addr; // } // test code int main(void) { output<<" in main function "<<endl; try{ try{ output<<"exhausting the heap"<<endl; int* p = new int(); while(p!=NULL){ p = new int(); } output<<" heap exhausted"<<endl; } catch(...){ /* never reach here because I use the --force_new_nothrow */ output<<"heap exhausted. and received an exception"<<endl; } output<<"now I throw an int"<<endl; throw int(); } catch(char){ output<<"catch a char"<<endl; } catch(int ){ output<<"catch an int"<<endl; } catch(...){ // output some debug imformation output<<"unkown exception"<<endl; } output<<"end"<<endl; while(1); }
Here is the output : __ARM_exceptions_init() in main function exhausting the heap heap exhausted now I throw an int catch an int end
if I un-comment the three functions and the global buf in the code, the output then becomes: __ARM_exceptions_init() __ARM_exceptions_buffer_init() in main function exhausting the heap heap exhausted now I throw an int __ARM_exceptions_buffer_allocate() catch an int __ARM_exceptions_buffer_free() end