On Linux, a file that is re-opened in readWrite mode can't be written to

[dymk]

Given this code:

import vibe.core.file;
import std.file;
import std.stdio;

void main() {
    string f = "testbugfile";

    scope(exit) { remove(f); }
    if(exists(f))
        remove(f);

    auto handle = openFile(f, FileMode.createTrunc);
    handle.write(cast(ubyte[])[1, 2, 3]);

    handle.close();

    handle = openFile(f, FileMode.readWrite);
    handle.write(cast(ubyte[])[5, 6, 7]);
}

The code will fail on line 18, with the error:

object.Exception@vendor/vibe-d/source/vibe/core/drivers/threadedfile.d(182): Failed to write data to disk.3 9 -1 8
----------------
./fileerr(pure @safe bool std.exception.enforce!(bool).enforce(bool, lazy const(char)[], immutable(char)[], ulong)+0x5e) [0x5b1b2a]
./fileerr(void vibe.core.drivers.threadedfile.ThreadedFileStream.write(const(ubyte[]))+0xe6) [0x52c102]
./fileerr(_Dmain+0x141) [0x51f35d]
./fileerr(void rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).runMain().void __lambda1()+0x18) [0x59d6ac]
./fileerr(void rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).tryExec(scope void delegate())+0x2a) [0x59cee6]
./fileerr(void rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).runMain()+0x27) [0x59d66b]
./fileerr(void rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).tryExec(scope void delegate())+0x2a) [0x59cee6]
./fileerr(_d_run_main+0x1a3) [0x59ce67]
./fileerr(main+0x17) [0x51f99b]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf5) [0x7f5e5b333ea5]

After some googling, it seems that error code 9 (the 9 in 3 9 -1 8 as found here. However, it's also listed as EBADF, according to this. I'm not sure which one the 9 here refers to.

I'm not particularly sure why this would happen; it seems that calling .close() on the handle would close the underlying fd, according to threadedfile.d. Weird.

[s-ludwig]

Testing on Linux confirms that the missing O_RDWR was the cause.

BTW for me it was already the first write that failed. It never got to open the file for a second time.