Expect error if closing a file twice with ::close and ::fclose sequentially, but got nothing #22033
Description
Please include the following in your bug report:
Version of emscripten/emsdk:
3.1.54
Failing command line in full:
# emscripten:
emcc close_fclose.cpp -o main.js --preload-file ./temp.txt; node main.js
# g++:
g++ close_fclose.cpp -o main; ./main
Hi, I found a problem regarding the behaviour of ::fclose and ::close.
Basically, if we first close a file with ::close, then call ::fclose to close it again, it is definitely a behavior not allowed and should report errors via errno and the return value of the ::fclose should be EOF according to https://man7.org/linux/man-pages/man3/fclose.3.html#RETURN_VALUE.
However, it seems such operations don't set anything with errno, and the return value of ::fclose is also not set as EOF, as shown below, which seems to be weird. Besides, if we reverse the order of ::close and ::fclose (i.e., first execute ::fclose, then ::close), then I could get a correct error message via errno and the return value of ::close is EOF. So it's quite weird.
It'd be so appreciated if you could help check it. Thank you!
Code
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
int main() {
FILE* f = ::fopen("temp.txt", "r");
int fd = fileno(f);
// interesting: if call fclose(f) before close(fd), it could reports error
int ret_1 = close(fd);
int ret_2 = fclose(f);
printf("error: %s\n", strerror(errno));
printf("ret_of_close is: %d, ret_of_fclose is: %d\n", ret_1, ret_2);
return 0;
}Result
Here we can see in wasm execution results, there is no error information, and the return value of ::fclose is also not EOF.
# emscripten
error: No error information
ret_of_close is: 0, ret_of_fclose is: 8
# g++
error: Bad file descriptor
ret_of_close is: 0, ret_of_fclose is: -1