I have a C library and I need to access its functions in a Perl program.
I researched this on the internet and find that this wrapper can be implemented using XS, but I saw that XS is not consistent if needed to run the code on different OS.
I also found module FFI::Raw on CPAN which might do the job. Does anyone use FFI::Raw in production? What do you suggest to use, FFI::Raw or XS?
Related
I want to write a small assembly code and call it from Perl :
I look at cpan and find those 2 Perl modules
https://metacpan.org/pod/Inline::ASM which is very old
https://metacpan.org/pod/FFI::Platypus::Lang::ASM which mention that it possible to call assembly from perl , i look at the examples but didn't find any example related to assembly code.
any idea how to use FFI::Platypus::Lang::ASM with Perl , an example will be appreciated
any idea how to use FFI::Platypus::Lang::ASM with Perl , an example will be appreciated
The author of that module hasn't provided any examples for that code themselves. It looks like it may be an unfinished project.
Anyways, this is a pretty odd thing to want to do. Perl operates a couple levels of abstraction away from assembly -- interoperation between them is awkward at best.
A more practical solution will be to write C code which calls into your assembly code (or embeds it as inline assembly), then adapt that code to Perl using XS.
I have a project written in C which I wish to convert to Perl. A friend of mine suggested to use LLVM. I compiled my C code to LLVM assembly using Clang. Now I'm trying to convert this intermediate representation into Perl but I can't seem to find any backend for it. Would someone point me in the right direction?
No, there isn't such a backend. At least not directly. Emscripten converts LLVM IR to Javascript, and maybe you can use something else to convert that to Perl.
It's a pretty bad idea for moving a project from one language to another. The code will be completely unreadable and un-maintainable. Either do a honest rewrite or wrap your C as a library with Perl's foreign-function interface tools and use it from Perl.
Converting to Perl is a no go. It hasn't been done because emulating C in Perl would be insanely slow. They have completely different type systems, for starters. However, it's wholly unnecessary to convert the code to Perl to call it from Perl. You can load compiled C code from Perl.
What you'll have to do is tell Perl how to call those C functions. Perl deals with scalars and so on, but C deals with ints and so on. This is done using XS.
perlxstut contains the documentation on how to do all this.
I am trying to better understand logic and flow of exceptions. So i got to state that i really feeled lack of understanding how Perl interpretes and runs programs, which phases are involved and what happens on every phase.
For example, I'd like to understand, when are binded STD* IO and when released, what is happening with $SIG{*} things, how they are depended with execepions, how program dies, etc. I'd like to have better insight of internals mechanics.
I am looking for links or books. I prefer some material which has also visual charts involved but this is not mandatory. I'd like to see some "big picture" of whole process, then i have already possibilities to dig further if i find it necessary.
I found Chapter 18th in Programming Perl gives overview of compiling phase and i try to work it trough, but i appreciate other good sources too.
Some alternative sources (there are not very many):
Mannning's Extending and Embedding Perl, which is the go-to reference on Perl's internals outside of the source
The chapter on the Perl internals in Advanced Perl Programming, which may be exactly what you want
Simon Cozens's Perl internals FAQ
Those may be more focused to what you're looking for. I'm not sure any of them explicitly spells out the interpreter's runtime execution order, though. The first one is a better "I want to work with this stuff" book; the second two are probably good introductory references.
Some of the questions you ask are not, as far as I know, explicitly documented - the I/O question being one I can't think of a good source for in particular. Exception handling is documented very well in Try::Tiny's documentation, and it's what we use for exceptions. Signal handling is messy, but perlipc documents it pretty well. With threads, you may be stuck with unsafe signals - I generally avoid threads in favor of multiple processes unless I must have shared memory.
You might start with these topics accessible via the perldoc program:
Internals and C Language Interface
perlembed Perl ways to embed perl in your C or C++ application
perldebguts Perl debugging guts and tips
perlxstut Perl XS tutorial
perlxs Perl XS application programming interface
perlxstypemap Perl XS C/Perl type conversion tools
perlclib Internal replacements for standard C library functions
perlguts Perl internal functions for those doing extensions
perlcall Perl calling conventions from C
perlmroapi Perl method resolution plugin interface
perlreapi Perl regular expression plugin interface
perlreguts Perl regular expression engine internals
perlapi Perl API listing (autogenerated)
perlintern Perl internal functions (autogenerated)
perliol C API for Perl's implementation of IO in Layers
perlapio Perl internal IO abstraction interface
perlhack Perl hackers guide
perlsource Guide to the Perl source tree
perlinterp Overview of the Perl interpreter source and how it works
perlhacktut Walk through the creation of a simple C code patch
perlhacktips Tips for Perl core C code hacking
perlpolicy Perl development policies
perlgit Using git with the Perl repository
I have gone through the source code of Data::Dumper. In this package I didn't understand what's going on with DumpXS. What is the use of this DumpXS?
I have searched about this and I read that, it is equal to the Dump function and it is faster than Dump. But I didn't understand it.
The XS language is a glue between normal Perl and C. When people want to squeeze every last bit of performance out of an operation, they try to write it as close to the C code as possible. Python and Ruby have similar mechanisms for the same reason.
Some Perl modules have an XS implementation to improve performance. However, you need a C compiler to install it. Not everyone is in a position to install compiled modules, so the modules also come in a "PurePerl" or "PP" version that does the same thing just a bit slower. If you don't have the XS implementation, a module such as Data::Dumper can automatically use the pure Perl implementation. In this case, Data::Dumper also lets you choose which one you want to use.
A lot of Perl modules have "XS" versions, like JSON::XS. The XS in the name means that it partly uses C in order to increase the speed or other efficiency of the module. I don't know this particular case, but it is probably that.
And if you want a bit more info on XS go to http://perldoc.perl.org/perlxs.html
But I am curious what lead you to this question.
I'm looking for some tutorials showing how I could test C programs by writing Perl programs to automate testing.
Basically I want to learn automation testing with Perl programs. Can anyone kindly share such tutorials or any experiences of yours which can help me kick-start this process?
Perl tests usually use TAP. There are a several C libraries for TAP. Watch this Perl testing presentation.
If you want to start learning how to use Perl to test external programs, start with learning to use Perl to test Perl bits. The Test::More module is a good place to start. Once you understand that, look at all of the other Test::* modules on CPAN to see if one of those modules does the sort of thing you need to do.
If you have a specific question, ask about that. This question is really too broad for anyone to provide a useful answer.
You should look at Perl Testing: A Developer's Notebook by chromatic and Ian Langworth.
I keep meaning to buy a copy but as yet I've just skimmed it at perlmongers meetings. But it seems to be spot on what you're looking for.
UPDATE:
Hm, and this shows I should read the question - testing C programs with Perl, not testing Perl programs with Perl.
The book may still be useful (in that you should probably be writing test scripts and using Test::More and friends) but you will need to write a set of Perl functions to control your C if you take that approach. Basically
sub run_my_c_program {
my #args=#_;
#Set up test environment according to #args
system "my-c-program";
# Turns restults into a $rv data structure
return $rv;
}
and then check $rv in the same way as a normal Perl test:
is_deeply(run_my_c_program(...),
{ .. what I think it returns ..},
".. description of what I'm testing ..");
I don't have a tutorial but I used to be on a test team that tested a C++ compiler. The test harness (home brewed) we used was written in perl and it worked for us for many years. Perl was ideal because we could easily use it to invoke the tools to build the program, capture the output for later insertion into our test logs (using the "backticks" to run the compiler. For example: $compilerOutput = `cl -?`;
), then, if the build was successful, run the test programs and capture their output, again for insertion into our test logs.
Other benefits we got from using Perl:
For pass/fail detection, Perl's regular expression support was helpful.
Our program (the compiler) was ported during the course of its life to many different hardware architectures. Since Perl source was available and in C, we could get perl running on a new architecture as soon as a C compiler was available (which is usually the first language implemented in a new environment after an assembler).
Lots of documentation, books, help available.
-Ron
I wrote an article about Testing C with Libtap that uses Perl's Test::Harness to test C programs. Here's an example project: https://github.com/stig/libggtl/tree/master/t -- might not build any more, as the esoteric build system probably doesn't exist, but you should be able to figure out how it works :-)