C++ iostream only working in Init, not in other RTEMS Tasks

Thu May 4 06:42:32 UTC 2017

Hello,

We are configuring maximum 64 file descriptors at the moment:

…
#define CONFIGURE_APPLICATION_EXTRA_DRIVERS DYPLO_DRIVER_TABLE_ENTRY
#define CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER
#define CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER
#define CONFIGURE_MAXIMUM_DRIVERS 10

#define CONFIGURE_EXECUTIVE_RAM_SIZE    (128*1024*1024)
#define CONFIGURE_STACK_SPACE_SIZE      (10*1024*1024)

#define CONFIGURE_UNLIMITED_OBJECTS

#define CONFIGURE_INIT_TASK_STACK_SIZE  (1024*1024)
#define CONFIGURE_INTERRUPT_STACK_SIZE                (32*1024)
#define CONFIGURE_MINIMUM_TASK_STACK_SIZE (32*1024)
#define CONFIGURE_MAXIMUM_TASKS                               3
#define CONFIGURE_MAXIMUM_SEMAPHORES           64
#define CONFIGURE_RTEMS_INIT_TASKS_TABLE
#define CONFIGURE_MICROSECONDS_PER_TICK 1000

#define CONFIGURE_APPLICATION_NEEDS_LIBBLOCK
#define CONFIGURE_LIBIO_MAXIMUM_FILE_DESCRIPTORS 64
#define CONFIGURE_USE_IMFS_AS_BASE_FILESYSTEM
#include <rtems/confdefs.h>

#define CONFIGURE_SHELL_COMMANDS_INIT
#define CONFIGURE_SHELL_COMMANDS_ALL
#include <rtems/shellconfig.h>
…

From: users [mailto:users-bounces at rtems.org] On Behalf Of Joel Sherrill
Sent: woensdag 3 mei 2017 22:42
To: Sebastian Huber
Cc: rtems-users at rtems.org
Subject: Re: C++ iostream only working in Init, not in other RTEMS Tasks

On Wed, May 3, 2017 at 12:46 AM, Sebastian Huber <sebastian.huber at embedded-brains.de<mailto:sebastian.huber at embedded-brains.de>> wrote:
On 03/05/17 07:15, Sebastian Huber wrote:
On 03/05/17 00:47, Chris Johns wrote:
On 2/5/17 6:03 pm, Sebastian Huber wrote:
On 02/05/17 09:35, Chris Coppens wrote:
Hello,

In our RTEMS application C++ iostream (e.g. "cout") is only working in
the “Init” function?
If I use “cout” in a RTEMS Task other than Init, no output is shown in
the console.
Any idea why this is happening?
The C++ library uses thread-local standard IO streams (Newlib feature)
for the global IO stream objects. I am not sure how to fix this
properly, but I guess a RTEMS-specific change in the libstdc++ would be
necessary.
Does a ticket exist for this? This should be fixed for 4.12.0 so please
set the milestone to 4.12.0 and blocker.

I don't know if a ticket exists. This issue exits in all RTEMS versions with C++ support. Since the initialization thread is restarted after the C++ global constructor calls this issue is more obvious now.

Before you make this a release blocker, then please find someone who can fix this.

Just for reference. The std::cout etc. is initialized here

https://gcc.gnu.org/viewcvs/gcc/trunk/libstdc%2B%2B-v3/src/c%2B%2B98/ios_init.cc?view=markup#l85

via a placement new. The "stdout" etc. is thread-local in Newlib. Using this for a global object like std::cout is quite broken.

Is there a test program to demonstrate that this is broken?

Since Cygwin also uses newlib, I have trouble believing this would
not also be broken there.

Going back to the original post. How many file descriptors are configured?
I am suspicious that the way C++ does it might require more file descriptors.

--joel

--
Sebastian Huber, embedded brains GmbH

Address : Dornierstr. 4, D-82178 Puchheim, Germany
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E-Mail  : sebastian.huber at embedded-brains.de<mailto:sebastian.huber at embedded-brains.de>
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Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.

Kind regards,

Chris Coppens

Software Designer

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