Writing to an unlinked file causes errors #6128
Description
Describe the bug
Writing to a file descriptor of an unlinked file causes an error with the reason that the file does not exist. On POSIX systems this should work.
For temporary files it is a common pattern to create the temporary file, obtain a fd, unlink the path, and then just use the fd. For example python does it that way.
Steps to reproduce
Using the following test file
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
int main() {
int fd = open("/tmp/test.txt", O_CREAT | O_WRONLY | O_TRUNC, 0644);
if (fd == -1) {
perror("open");
return 1;
}
printf("open succeeded\n");
// 1. The file needs to be unlinked
unlink("/tmp/test.txt");
if (errno != 0) {
perror("unlink");
return 1;
}
printf("unlink succeeded\n");
FILE* fp = fdopen(fd, "wr");
if (fp == NULL) {
perror("fdopen");
return 1;
}
printf("fdopen succeeded\n");
// 2. The write must be larger than 1024 bytes. Smaller writes succeed for some reason.
char memory_buffer[1025];
size_t n = fwrite(memory_buffer, 1, 1025, fp);
if (ferror(fp)) {
perror("fwrite");
return 1;
}
printf("writing succeeded\n");
close(fd);
return 0;
}with the above file stored as repro.c, run
wasixcc repro.c -o repro
cargo run -p wasmer-cli --features llvm,wasmer-artifact-create,static-artifact-create,wasmer-artifact-load,static-artifact-load -- ./repro
Expected behavior
The program exits with 0 and outputs:
open succeeded
unlink succeeded
fdopen succeeded
writing succeeded
Actual behavior
The program exits with 1 and outputs:
open succeeded
unlink succeeded
fdopen succeeded
fwrite: No such file or directory
Additional context
You can verify the expected behaviour by compiling and running it as native code.
clang repro.c -o repro.bin
./repro.bin