llvm dev - Jul 2013 - [LLVMdev] Passing String to an external function in llvm

I have one file named hashtable.cpp whose link is 
"http://pastebin.com/Cq2Qy50C"

and one llvm pass named testing.cpp whose link is
"http://pastebin.com/E3RemxLF"

Now on this testing.cpp pass I have computed the string named "expr"
which I
want to pass to the function named hashtable(string) in hashtable.cpp   (on
line 106 of testing.cpp)

> looking at simple examples of code compiled by Clang should give you an
> idea of what instructions you need to emit. 
I did try but not able to pass the string.

If you could go through my code it will be of great help. Thanx



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On Thu, Jul 25, 2013 at 11:40 AM, Abhinash Jain <omnia at mailinator.com>
wrote:
> I have one file named hashtable.cpp whose link is
> "http://pastebin.com/Cq2Qy50C"
>
> and one llvm pass named testing.cpp whose link is
> "http://pastebin.com/E3RemxLF"
>
> Now on this testing.cpp pass I have computed the string named
"expr" which I
> want to pass to the function named hashtable(string) in hashtable.cpp   (on
> line 106 of testing.cpp)
>
>
>> looking at simple examples of code compiled by Clang should give you an
>> idea of what instructions you need to emit.
>
> I did try but not able to pass the string.
>
> If you could go through my code it will be of great help. Thanx
OK - seems you might want to take a few steps back & understand how
C++ code is written/structured generally (and/or take a look at other
parts of the compiler). You'll need a header file with the declaration
of your function & you can include that header file in the
hashtable.cpp and testing.cpp - if that sentence doesn't make sense to
you yet, please find some general C++ programming resources to provide
further detail as such a discussion isn't really on-topic here.

- David

> OK - seems you might want to take a few steps back & understand how
> C++ code is written/structured generally (and/or take a look at other
> parts of the compiler). You'll need a header file with the declaration
> of your function & you can include that header file in the
> hashtable.cpp and testing.cpp - if that sentence doesn't make sense to
> you yet, please find some general C++ programming resources to provide
> further detail as such a discussion isn't really on-topic here. 
I know it could be a bit frustrating for you to answer such foolish
question, but am novice to llvm and desperately need some help to resolve
this issue.

testing.cpp is an instrumentation file of llvm, whereas hashtable.cpp is
simple c++ code.

I want to insert the function named hashtable() (which is already present in
hashtable.cpp) after every store instruction.
So I have to first DECLARE it,  which can be done with getOrInsertFunction()
in testing.cpp.
Now since declaration of function hashtable() is like 

void hashtable(string expr)    //in hashtable.cpp

So in getOrInsertFunction() I have to pass some more details like

getOrInsertFunction (name of function in IR, Return type of function, List
of argument for the function, etc.)
i.e. getOrInsertFunction("_Z14printHashTablev",
Type::getVoidTy(M.getContext()), ????, ????,);

Now hashtable() function takes string as an argument, so what should I write
in place of ???? above.

And than how should I actually CALL that hashtable() function with the help
of methods 
like CallInst::Create, getInstList().insert etc.



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