Error -128 calling k(0, ...) from same process

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1

In my shared object I have

K ret = k(0, (S)“0N!`hello”, (K)0);

If I call the above code from the current process I receive ret == -128 and ret->s will return (null). However, if I open two processes, one listening on port 5010 and another process with the code

K handle = kph((S)“localhost”, 5010);

K ret = k(0, (S)“0N!`hello”, (K)0);

There are no problems, and the process running on port 5010 will as expected print 

`hello

`hello

Any ideas why I can run the code in the same process?

2

for a shared object, do not link with c.o as those functions etc already exist within the kdb+ process.

3

Thanks Charles. How can I compile anything without linking to c.o?

I can send the data from one q process to another, but not to itself where the shared object is loaded, i.e. k(0,…)?

4

Apologies, the code above should read

K handle = kph((S)“localhost”, 5010);

K ret = k(handle, (S)“0N!`hello”, (K)0);

5

to create a shared lib on linux using gcc, the cmd line for compiling would be

gcc -DKXVER=3 a.c -o a.so -fPIC -shared

the functions such as ktn etc are resolved when loading into kdb+.

6

btw, for developing shared libs, refer to

http://code.kx.com/wiki/Cookbook/ExtendingWithC

noting that if you are developing a lib to load into kdb+2.x define KXVER=2

and for v3.x define KXVER=3

7

Thanks a lot!

One more issue: My dynamic shared object does not contain any exported symbols. My C++ code contains some functions that are defined like extern “C” myfunc(). From the terminal I can see that myfunc() is not being exported:

nm -f feed_handler.so

U dyld_stub_binder


file feed_handler.so

         feed_handler.so: Mach-O dynamically linked shared library i386

Is my compilation messed up?

8

can you provide a very simple test cpp file, .e.g

#include"k.h"

extern “C” K f(K x){R (K)0;}

and your compile cmd line?

and compiler version

9

Ok, so I can compile your example. However, if I use other functions such as k(), ki(), khp(), etc. I’m getting ‘Undefined symbols’:

#include “k.h”

extern “C” K f(K x){R (K)0;}

extern “C” K add(K x,K y)

{

R ki(x->i+y->i);

}

compiling:


clang++ -DKXVER=3 -m32 -fPIC -shared -stdlib=libc++ -std=c++11 test.cpp -o test.so

Undefined symbols for architecture i386:

“_ki”, referenced from:

_add in test-d49315.o

ld: symbol(s) not found for architecture i386

clang: error: linker command failed with exit code 1 (use -v to see invocation)

10

i think you need

-undefined dynamic_lookup 

11

Thanks a lot Charles