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2003-10-02 Chris Caudle <chris@chriscaudle.org>

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* nextstep.t: RTEMS applications can now use main() so correct the
	discussion of this.
This commit is contained in:
Joel Sherrill
2003-10-02 16:58:12 +00:00
parent 150505b278
commit d134469909
1 changed files with 34 additions and 18 deletions
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52
doc/started/nextstep.t
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@@ -83,12 +83,29 @@ at @uref{@value{RTEMSHTTPURL}/support.html,@value{RTEMSHTTPURL}/support.html}.
@section Writing an Application
From an application author's perspective, RTEMS applications do not
start at @code{main()}. They begin execution at one or more
application initialization task or thread and @code{main()} is
owned by the Board Support Package. Each API supported
by RTEMS (Classic, POSIX, and ITRON) allows the user to configure
a set of tasks that are created and started automatically
From an application author's perspective, the structure of
an RTEMS application is very familiar. In POSIX language,
RTEMS provides a single process, multi-threaded run-time
environment. However there are two important things that are
different from a standard UNIX hosted program.
First, the application developer must provide configuration
information for RTEMS. This configuration information
includes limits on the maximum number of various OS resources
available and networking configuration among other things.
See the @b{Configuring a System} in the
@b{RTEMS Applications C User's Guide} for more details.
Second, RTEMS applications may or may not start at
@code{main()}. Applications begin execution at
one or more user configurable application
initialization tasks or threads. It is possible
to configure an application to start with a
single thread that whose entry point is @code{main()}.
Each API supported by RTEMS (Classic, POSIX, and ITRON)
allows the user to configure a set of one or more tasks
that are created and started automatically
during RTEMS initialization. The RTEMS Automatic
Configuration Generation (@code{confdefs.h}) scheme can be
used to easily generate the configuration information for
@@ -104,19 +121,18 @@ initialization task varies based up API.
@item @code{ITRON_Init} - single ITRON API Initialization Task
@end itemize
See the Configuring a System chapter in the C User's Guide for
more details.
Regardless of the API used, when the initialization task executes,
all non-networking device drivers are normally initialized and
processor interrupts are enabled. The initialization task then
goes about its business of performing application specific
initialization. This often involves creating tasks and other
system resources such as semaphores or message queues and allocating
memory. In the RTEMS examples and tests, the file @code{init.c} usually
contains the initialization task. Although not required, in
most of the examples, the initialization task completes by
deleting itself.
all non-networking device drivers are normally initialized,
processor interrupts are enabled, and any C++ global constructors
have been run. The initialization task then goes about its
business of performing application specific initialization which
will include initializing the networking subsystem if it is to be
used. The application initialization may also involve creating
tasks and other system resources such as semaphores or message queues
and allocating memory. In the RTEMS examples and tests, the
file @code{init.c} usually contains the initialization task. Although
not required, in most of the examples, the initialization task
completes by deleting itself.
As you begin to write RTEMS application code, you may be confused
by the range of alternatives. Supporting multiple tasking