Exploratory Project in Linux

Exploratory Project in Linux

Overview:

The conversion of the Exploratory Project (EP) from Windows to Linux has been completed.

That is, as far as its framework is concerned and communications between User Applications via named pipes (as the replacement for Microsoft MS Pipes).  The Display Application that is the A661 protocol application that is the graphical user interface (GUI) has yet to be done.  This will be a bigger conversion since the Windows version written in Visual C# cannot be used while just applying Linux interface procedures to replace those to Windows via Win32Ada – so an entirely new application will need to be written.

There are three user applications that communicate with each other.  Each uses the EP framework that manages the registration of worker components and the delivery of instances of topic message instances from the topic producer component to the consumer component.  The consumer component can be in the same user application (Linux process) as the producer or in one of the other two user applications.  It makes no difference since a remote registration phase of the system startup finds the remote applications that have components that consume (or produce) the topic.  The framework will delivery the topic within the local application or remotely or both.  The number of possible consumers (and publishers) depends upon the topic method of Message Exchange. 

See earlier (pre-Linux) posts for more information about the framework and the user applications.

Besides the Display application, another feature of the Windows version that remains unimplemented is the ability to use the TCP/IP protocol for inter-application communications.  The Windows version uses WinSock(ets) whereas, like MS Pipes, a Linux interface will need to be used instead.

Design:

One design change was to eliminate the use of Microsoft Mailslots to determine which of the possible remote applications identified in the configuration file are actually running and so can be communicated with. 

The use of mailslots was no longer necessary after I discovered the Win32 interface to provide the running processes but it was never removed.  Now for the Linux version with its version of my Is_Running executive interface function (see a previous post) it has been.

The Linux implementation uses a revised version of the Ada mc-exec package to act as an interface to the executive / operating system.  It also replaces the use of the Win32Ada package to provide an interface with the Windows operating system with the use of a new exec_itf package.  These have been described in previous posts.

The framework and the worker component code remains unchanged except where a reference to a Win32Ada procedure/function had to be replaced to a reference to the new exec_itf.  This flaw in the Windows version can be fixed by the use of a Windows version of exec_itf to be the direct interface to the Win32Ada procedures – that is, the use of another interface layer so that the framework code can be free of operating system dependencies.

Implementation:

The third user application (app3) has a combination of Ada, C, and C++ components.  Therefore, the GNAT builds that I had been using had to be revised since just building the GNAT project via gnatmake wasn't working (as it had not been working in Windows using GNAT GPS).  Even thou the use of C and C++ in addition to Ada were specified in the project, both GPS and the Linux gnatmake that referenced the project failed to cause the C and C++ files to be compiled and linked.

Therefore, I used a build file (xyapp3) in my bin folder to do the build for app3.  This file is as follows.

#

# add particular ada files to the library that are referenced by C or C++

cd /home/clayton/Source/EP/Object3

rm libapp3.a

g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA -I/home/clayton/Source/EP/Util /home/clayton/Source/EP/Ada/A661UA/App3/com_periodic.adb -o com_periodic.o

g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA -I/home/clayton/Source/EP/Util /home/clayton/Source/EP/Ada/A661UA/mt-topic_periodic.adb -o mt-topic_periodic.o

g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA -I/home/clayton/Source/EP/Util /home/clayton/Source/EP/Ada/A661UA/mt-topic_n_to_one_1.adb -o mt-topic_n_to_one_1.o

ar rc libapp3.a com_periodic.o mt-topic_periodic.o mt-topic_n_to_one_1.o

#

# do the gnatmake

cd /home/clayton/Source/EP/Ada/A661UA

gnatmake -c -Papp3.gpr

#

# do xyapp3c to compile C and C++, add to the library, and do the bind and link

xyapp3c

where xyapp3c is

# change directory/folder to Object3

cd /home/clayton/Source/EP/Object3

pwd

# g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA -I/home/clayton/Source/EP/Util /home/clayton/Source/EP/Util/console.adb -o /home/clayton/Source/EP/Object3/console.o

# g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA -I/home/clayton/Source/EP/Util /home/clayton/Source/EP/Ada/A661UA/App3/com_periodic.adb -o /home/clayton/Source/EP/Object3/com_periodic.o

# rm /home/clayton/Source/EP/Object3/libapp3.a

# ar rc /home/clayton/Source/EP/Object3/libapp3.a /home/clayton/Source/EP/Object3/com_periodic.o

g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA /home/clayton/Source/EP/Ada/A661UA/App3/app_initializeada.c -o /home/clayton/Source/EP/Object3/app_initializeada.o

g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA /home/clayton/Source/EP/Ada/A661UA/mt-topic.c -o /home/clayton/Source/EP/Object3/mt-topic.o

g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA /home/clayton/Source/EP/Ada/A661UA/mt-topicnto1.c -o /home/clayton/Source/EP/Object3/mt-topicnto1.o

g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA /home/clayton/Source/EP/Ada/A661UA/mt-topic1ofn.c -o /home/clayton/Source/EP/Object3/mt-topic1ofn.o

g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA -I/home/clayton/Source/EP/Ada/A661UA/App3 /home/clayton/Source/EP/Ada/A661UA/App3/mt-topicperiodic.c -o /home/clayton/Source/EP/Object3/mt-topicperiodic.o

g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA /home/clayton/Source/EP/Ada/A661UA/mt-topiccontentfiltered.c -o /home/clayton/Source/EP/Object3/mt-topiccontentfiltered.o

g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA -I/home/clayton/Source/EP/Ada/A661UA/App3 /home/clayton/Source/EP/Ada/A661UA/App3/comc1.c -o /home/clayton/Source/EP/Object3/comc1.o

g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA -I/home/clayton/Source/EP/Ada/A661UA/App3 /home/clayton/Source/EP/Ada/A661UA/App3/comc2.c -o /home/clayton/Source/EP/Object3/comc2.o

g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA -I/home/clayton/Source/EP/Ada/A661UA/App3 /home/clayton/Source/EP/Ada/A661UA/App3/component.cpp -o /home/clayton/Source/EP/Object3/component.o

g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA -I/home/clayton/Source/EP/Ada/A661UA/App3 /home/clayton/Source/EP/Ada/A661UA/App3/app_initializec.c -o /home/clayton/Source/EP/Object3/app_initializec.o

g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA -I/home/clayton/Source/EP/Ada/A661UA/App3 /home/clayton/Source/EP/Ada/A661UA/App3/appc++.cpp -o /home/clayton/Source/EP/Object3/appc++.o

g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA -I/home/clayton/Source/EP/Ada/A661UA/App3 /home/clayton/Source/EP/Ada/A661UA/App3/app_initializecpp.c -o /home/clayton/Source/EP/Object3/app_initializecpp.o

g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA -I/home/clayton/Source/EP/Ada/A661UA/App3 /home/clayton/Source/EP/Ada/A661UA/App3/com3c.cpp -o /home/clayton/Source/EP/Object3/com3c.o

g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA -I/home/clayton/Source/EP/Ada/A661UA/App3 /home/clayton/Source/EP/Ada/A661UA/mt_topic.cpp -o /home/clayton/Source/EP/Object3/mt_topic.o

g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA -I/home/clayton/Source/EP/Ada/A661UA/App3 /home/clayton/Source/EP/Ada/A661UA/mt_topic_n_to_one_1.cpp -o /home/clayton/Source/EP/Object3/mt_topic_n_to_one_1.o

g++ -c -g -I/home/clayton/Source/EP/Ada/A661UA -I/home/clayton/Source/EP/Ada/A661UA/App3 /home/clayton/Source/EP/Ada/A661UA/App3/mt_topic_periodic.cpp -o /home/clayton/Source/EP/Object3/mt_topic_periodic.o

cd /home/clayton/Source/EP/Object3

ar rc libapp3.a com3c.o

ar rc libapp3.a appc++.o app_initializec.o app_initializecpp.o app_initializeada.o

ar rc libapp3.a mt-topic.o mt-topicnto1.o mt-topic1ofn.o mt-topicperiodic.o mt-topiccontentfiltered.o mt_topic.o mt_topic_n_to_one_1.o mt_topic_periodic.o

ar rc libapp3.a comc1.o comc2.o component.o

#

gnatbind -x app3.ali

gnatlink app3.ali libapp3.a --LINK=c++ -o app3.exe

The use of the libapp3.a library means that the large number of .o object files for the C and C++ code do not need to be included in the gnatlink line. 

The use of the --LINK=c++ parameter in the gnatlink command avoids a __gxx_personality_v0 problem that otherwise occurs with the mixture of Ada and C++. 

When I searched the internet about the gxx_personality error after I got it there were a number of Linux commentators giving their take on a fix – such as creating a particular dummy routine to satisfy the linker and avoid getting the error.  However, GNAT itself said to use

--LINK=c++ and that fixed the gxx_personality error without the suggested hijinks of the Linux fixers. 

The above files pretty much mimic my Windows .bat batch file to do the compile and build except for the use of --LINK=c++.  For the Windows version a special GNAT supplied library (C:\GNAT\2011\lib\gcc\i686-pc-mingw32\4.5.3\libpsapi.a) was used although I don't remember if it was to fix a similar problem.