Re: Calling Ada from C (linux/gnat 4.3.2)

[Matt Grochowalski <matt@gwalski.com>]

On Tuesday, November 1, 2011 2:46:07 PM UTC-4, awdorrin wrote:
> I am trying to port a program originally written on VxWork to Linux.
> The main program is written in C and spawns new threads and in the new
> threads calls are made to Ada procedures.
> 
> In the original program, written with GreenHills AdaMulti, it appears
> that there was a call being made that I am assuming was initializing
> the Ada Runtime's task stack/control block (rts_init_task()) - however
> this is just a guess.
> 
> In the version of the program I am migrating, I was seeing things that
> made me believe that the Ada thread's did not have their stacks setup
> properly, so I added the -fstack-check flag to the build.
> 
> Now, the C program creates the new thread, which calls the ada
> procedure - and the moment the thread has an opportunity to run - the
> application exits with 'raised STORAGE_ERROR : stack overflow
> detected'
> 
> I cannot get gdb to provide me a backtrace, since the program exits.
> If I try to break on the ada procedure name, I get a break, but trying
> to 'step' or 'next' keeps me in the main thread until a 'sleep' call
> lets the other thread run - at which point it raises the exception.
> 
> I am assuming that the ada runtime is initializing and the
> STORAGE_ERROR is raised before it gets to execute any of the code in
> my Ada procedure.
> 
> I have been trying to search to find what the proper way would be to
> call an Ada procedure from a C pthread, but have had zero luck. I also
> have been unable to determine what the equivalent of the
> 'rts_init_task' would be with Gnat.
> 
> Any have any ideas?

I have a simillar question using GCC 4.5.0 (the vanilla GNU distribution rather than AdaCore's).

There doesn't seem to be any issues calling Ada procedures from threads created using pthread_create in C, but GDB shows system__secondary_stack__ss_mark returning the same value in all threads. Could this create race conditions?