os::malloc(size_t size)

• 引数で渡されたサイズ（単位はバイト）分のメモリを確保する

//(jdk7/hotspot/src/share/vm/runtime/os.cpp)
void* os::malloc(size_t size) {
  NOT_PRODUCT(inc_stat_counter(&num_mallocs, 1));
  NOT_PRODUCT(inc_stat_counter(&alloc_bytes, size));

  if (size == 0) {
    // return a valid pointer if size is zero
    // if NULL is returned the calling functions assume out of memory.
    size = 1;
  }

  NOT_PRODUCT(if (MallocVerifyInterval > 0) check_heap());

  //glibcのmalloc関数を呼び出す
  //malloc関数 http://linuxjm.sourceforge.jp/html/LDP_man-pages/man3/free.3.html
  u_char* ptr = (u_char*)::malloc(size + space_before + space_after);
#ifdef ASSERT
  if (ptr == NULL) return NULL;
  if (MallocCushion) {
    for (u_char* p = ptr; p < ptr + MallocCushion; p++) *p = (u_char)badResourceValue;
    u_char* end = ptr + space_before + size;
    for (u_char* pq = ptr+MallocCushion; pq < end; pq++) *pq = (u_char)uninitBlockPad;
    for (u_char* q = end; q < end + MallocCushion; q++) *q = (u_char)badResourceValue;
  }
  // put size just before data
  *size_addr_from_base(ptr) = size;
#endif
  u_char* memblock = ptr + space_before;
  if ((intptr_t)memblock == (intptr_t)MallocCatchPtr) {
    tty->print_cr("os::malloc caught, " SIZE_FORMAT " bytes --> " PTR_FORMAT, size, memblock);
    breakpoint();
  }
  debug_only(if (paranoid) verify_block(memblock));
  if (PrintMalloc && tty != NULL) tty->print_cr("os::malloc " SIZE_FORMAT " bytes --> " PTR_FORMAT, size, memblock);
  return memblock;
}