JNI is crashing the java in windows 7 -

i porting code linux windows , since there no support linux shared memory segments in java. hence, using java native interface (jni) access shared memory.it working fine on linux platform .

code shmget:

jniexport jint jnicall java_emulatorinterface_communication_shm_sharedmem_shmget (jnienv * env, jobject jobj, jint count,jint maxnumjavathreads,jint emuthreadsperjavathread,         jlong coremap, jint pid) {      uint64_t mask = coremap;      int size;//=sizeof(packet)*(count+5)*maxnumjavathreads*emuthreadsperjavathread;      char str[50];     int ptr;  #ifdef _win32     handle hmapfile; #endif     printf("hello");     size=sizeof(packet)*(count+5)*maxnumjavathreads*emuthreadsperjavathread;     /*if (sched_setaffinity(0, sizeof(mask), (cpu_set_t *)&mask) <0) {         perror("sched_setaffinity");     }*/       //set global variables     gcount = count;     gmaxnumjavathreads = maxnumjavathreads;     gemuthreadsperjavathread = emuthreadsperjavathread;      //size1 number of packets needed in segment.  #ifdef _win32      _itoa(pid,str,10);       hmapfile = createfilemapping(invalid_handle_value,         null, page_readwrite,         0,32, str);      if (hmapfile == null)     {           exit(1);     }     closehandle(hmapfile);      hmapfile = createfilemapping(invalid_handle_value,         null, page_readwrite,         0,size, str);      if (hmapfile == null)     {         printf("unable create shared mem file.");         exit(1);     }     if (hmapfile < 0)     {         return (-1);     }      /*     if((hmapfile = createfilemapping(invalid_handle_value,         null, page_readwrite,         0,size, str))<0)     {         printf("error window %d\n",size);         return (-1);     }     */     ptr=*((int*)(hmapfile));      return ptr;          ///////////////error in return type      #else 

if trying use other function in jni ,my java crashes.

error

# # fatal error has been detected java runtime environment: # #  exception_access_violation (0xc0000005) @ pc=0x000007feedf911be, pid=4696, tid=4216 # # jre version: java(tm) se runtime environment (8.0_77-b03) (build 1.8.0_77-b03) # java vm: java hotspot(tm) 64-bit server vm (25.77-b03 mixed mode windows-amd64 compressed oops) # problematic frame: # c  [jnishm.dll+0x11be] # # failed write core dump. minidumps not enabled default on client versions of windows # # error report file more information saved as: # d:\workspace\tejasminor\hs_err_pid4696.log # # if submit bug report, please visit: #   http://bugreport.java.com/bugreport/crash.jsp # crash happened outside java virtual machine in native code. # see problematic frame report bug. # 

can point out problem ?

you can't dereference handle file mapping object. make function return handle, in:

return (int)hmapfile; 

on 64 bits windows (with 64 bits jre/jni) handle type 64 bits wide, lower 32 bits significant, that's ok.

side notes:

1. don't use hmapfile < 0. if api fails, return value null.
2. are sure need try @ first 32 bytes file, close it? why?
3. you may want call getlasterror , test result against error_already_exists (if want able detect condition)