问题
In my programm I may close a file that is already close. What happen when I do a fclose on a file already close ?
And if you can't do so, how to know if a file is closed or open ?
回答1:
Calling fclose twice with the same stream is undefined behaviour - most likely crash. There is no way to check if FILE* has been closed already, so the safe solution is to set pointer to NULL as soon as it is closed:
fclose(fh);
fh = NULL;
Sources: "The value of a pointer to a FILE object is indeterminate after the associated file is closed" (C draft standard). "After the call to fclose(), any use of stream causes undefined behaviour." (The Single UNIX ® Specification).
来源：https://stackoverflow.com/questions/24555980/fclose-a-file-that-is-already-fclose