struct _IO_FILE { int _flags; /* High-order word is _IO_MAGIC; rest is flags. */
/* The following pointers correspond to the C++ streambuf protocol. */ char *_IO_read_ptr; /* Current read pointer */ char *_IO_read_end; /* End of get area. */ char *_IO_read_base; /* Start of putback+get area. */ char *_IO_write_base; /* Start of put area. */ char *_IO_write_ptr; /* Current put pointer. */ char *_IO_write_end; /* End of put area. */ char *_IO_buf_base; /* Start of reserve area. */ char *_IO_buf_end; /* End of reserve area. */
/* The following fields are used to support backing up and undo. */ char *_IO_save_base; /* Pointer to start of non-current get area. */ char *_IO_backup_base; /* Pointer to first valid character of backup area */ char *_IO_save_end; /* Pointer to end of non-current get area. */
struct _IO_marker *_markers;
struct _IO_FILE *_chain;
int _fileno; int _flags2; __off_t _old_offset; /* This used to be _offset but it's too small. */
/* 1+column number of pbase(); 0 is unknown. */ unsignedshort _cur_column; signedchar _vtable_offset; char _shortbuf[1];
_IO_lock_t *_lock; #ifdef _IO_USE_OLD_IO_FILE };
struct _IO_FILE_complete { struct _IO_FILE _file; #endif __off64_t _offset; /* Wide character stream stuff. */ struct _IO_codecvt *_codecvt; struct _IO_wide_data *_wide_data; struct _IO_FILE *_freeres_list; void *_freeres_buf; size_t __pad5; int _mode; /* Make sure we don't get into trouble again. */ char _unused2[15 * sizeof (int) - 4 * sizeof (void *) - sizeof (size_t)]; };
fp->_wide_data->_wide_vtable = jmp; } else /* Cause predictable crash when a wide function is called on a byte stream. */ fp->_wide_data = (struct _IO_wide_data *) -1L; fp->_freeres_list = NULL; }
1
#define _IO_JUMPS(THIS) (THIS)->vtable
然后初始化FILE结构本身，将新的FILE链入链表中：
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void _IO_new_file_init_internal (struct _IO_FILE_plus *fp) { /* POSIX.1 allows another file handle to be used to change the position of our file descriptor. Hence we actually don't know the actual position before we do the first fseek (and until a following fflush). */ fp->file._offset = _IO_pos_BAD; fp->file._flags |= CLOSED_FILEBUF_FLAGS;
IO_validate_vtable (conststruct _IO_jump_t *vtable) { /* Fast path: The vtable pointer is within the __libc_IO_vtables section. */ uintptr_t section_length = __stop___libc_IO_vtables - __start___libc_IO_vtables; uintptr_t ptr = (uintptr_t) vtable; uintptr_t offset = ptr - (uintptr_t) __start___libc_IO_vtables; if (__glibc_unlikely (offset >= section_length)) /* The vtable pointer is not in the expected section. Use the slow path, which will terminate the process if necessary. */ _IO_vtable_check (); return vtable; }
/* In case this libc copy is in a non-default namespace, we always need to accept foreign vtables because there is always a possibility that FILE * objects are passed across the linking boundary. */ { Dl_info di; structlink_map *l; if (!rtld_active () || (_dl_addr (_IO_vtable_check, &di, &l, NULL) != 0 && l->l_ns != LM_ID_BASE)) return; }
#else/* !SHARED */ /* We cannot perform vtable validation in the static dlopen case because FILE * handles might be passed back and forth across the boundary. Therefore, we disable checking in this case. */ if (__dlopen != NULL) return; #endif
__libc_fatal ("Fatal error: glibc detected an invalid stdio handle\n"); }