On 10/23/23 10:16, Jon Leonard wrote:
On Mon, Oct 23, 2023 at 09:31:11AM -0400, Greg Wooledge wrote:
On Mon, Oct 23, 2023 at 11:15:22AM +0200, Thomas Schmitt wrote:
it helps to do
fflush((stdout);
after each printf(), or to run before the loop:
setvbuf(stdout, NULL, _IONBF, 0);
So it is obvious that the usual output buffering of printf() causes the
repetitions of text.
Yes, it looks like a buffering issue to me as well. Or, more generally,
some kind of weird interaction between buffered stdio FILEs and the
underlying Unix file descriptors, when new processes are being fork()ed.
More specifically, fork() does not play nicely with stdio buffering.
For performance reasons, stdio tends to read and write in chunks, reducing
the number of read() and write() calls. Some data is stored in the stdio
buffers, and that data is getting copied to both processes in the fork()
call.
If you want to mix fork() and stdio, be sure to flush buffers before the
call to fork. Depending on the task, it may be easier to use the underlying
read() and write() calls.
Jon Leonard
This thread seems related to a problem we've encountered when reloading
an edited file, forcing the user to use the file->open menu to reload a
program just edited, Using the file->reload doesn't always work, nor
does a mouse button marked reload, they both flip a quarter to decide if
you get the new code, or the old code that still exists in a cache
somewhere. Probably in /tmp under a hashed name. Is there a guaranteed
fix afoot that can be shared?
.
Cheers, Gene Heskett.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
