(send_process) [BROKEN_PTY_READ_AFTER_EAGAIN]:

Workaround for FreeBSD bug.  Flush output queue after EAGAIN in
write(2).

1 files changed, 26 insertions, 0 deletions

diff --git a/src/process.c b/src/process.c
index dab701a9e7f..aa83422f8c1 100644
--- a/src/process.c
+++ b/src/process.c
@@ -3431,6 +3431,32 @@ send_process (proc, buf, len, object)
                     Lisp_Object zero;
                     int offset;
 
+#ifdef BROKEN_PTY_READ_AFTER_EAGAIN
+                    /* A gross hack to work around a bug in FreeBSD.
+                       In the following sequence, read(2) returns
+                       bogus data:
+
+                       write(2)  1022 bytes
+                       write(2)   954 bytes, get EAGAIN
+                       read(2)   1024 bytes in process_read_output
+                       read(2)     11 bytes in process_read_output
+
+                       That is, read(2) returns more bytes than have
+                       ever been written successfully.  The 1033 bytes
+                       read are the 1022 bytes written successfully
+                       after processing (for example with CRs added if
+                       the terminal is set up that way which it is
+                       here).  The same bytes will be seen again in a
+                       later read(2), without the CRs.  */
+                    
+                    if (errno == EAGAIN)
+                      {
+                        int flags = FWRITE;
+                        ioctl (XINT (XPROCESS (proc)->outfd), TIOCFLUSH,
+                               &flags);
+                      }
+#endif /* BROKEN_PTY_READ_AFTER_EAGAIN */
+                    
                     /* Running filters might relocate buffers or strings.
                        Arrange to relocate BUF.  */
                     if (BUFFERP (object))