Hi all,
after digging into the apr_file_*() source code for Windows I have found
several issues regading file io and threading under Windows.
In general is there a document which explains which functions are
thread-safe and which not?
* Allocation of pOverlapped structure is not thread-safe (readwrite.c):
The allocation of the pOverlapped structure is not guarded by a mutex,
thus this can lead into undefined behavior (memory leak, resource leak
(CreateEvent)) if two threads enters apr_file_read()/apr_file_write()
at the same time!
Why not allocating this structure within apr_file_open() if XTHREAD was
specified?
* Usage of the mutex is not consistent.
Sometimes it is used with if(thefile->flags & APR_FOPEN_XTHREAD) and
sometimes without such an condition!
* apr_file_flush() for flushing the buffer does not use the mutex at all!
* apr_file_buffer_set() is broken (buffer.c).
The mutex is unconditionally used within apr_file_buffer_set(). But a
mutex is only created within apr_file_open() if APR_FOPEN_APPEND or
APR_FOPEN_BUFFERED is specified.
Also the docs of apr_file_buffer_set() documents that someone can
later add APR_FOPEN_BUFFERED support by calling it. But a mutex is
not created if it was not created by apr_file_open()!
* The preprocessor APR_HAS_THREADS inconsistently used.
Within filedup.c APR_HAS_THREADS is used to compile out some calls
to the apr_thread_*() functions and sometimes it is not used.
Any comments?
Regards,
Stefan
