Hi All,

I need to use a C++ so file in FreePascal. I have written a C wrapper for it, which successfully connected to Pascal.

Now my question is, can I use the $linklib directive to link the C-Wrapper STATICALLY, which in-turn use the shared so file? I tried to do this but it complained a lot of undefined references.

The key problem is, the {$linklib} instruction only tell FPC where to look for external functions in the C Wrapper, but how can I tell the linker to look for the ORIGINAL C++ so file to look for symbols required but not defined in the C-Wrapper?

My project is hosted at: https://github.com/xrfang/CTPas/

Thanks a lot.

Xiangrong

This is normal.

The key problem is, the {$linklib} instruction only tell FPC where to look for external functions in the C Wrapper, but how can I tell the linker to look for the ORIGINAL C++ so file to look for symbols required but not defined in the C-Wrapper?

{$linklib XYZ}

can be used for any library. So you should add the C wrapper library, C++ library, and probably some others as well, such as the C++ STL.

Michael.

Ok, but when I added these:

implementation
{$linklib libthostintf.a}
{$linklib thostmduserapi.so}
end.

I got:

/usr/bin/ld: cannot find -lthostmduserapi

All the required .so and .a file are in CURRENT dir.

2013/9/21 Michael Van Canneyt

1) Did you give the correct name ?
2) Is the current dir in the linker search path ? AFAIK the current dir is by default not in the linker search path.

Michael.

I am sure the name is correct. No matter I supply the linker path (-Fl.) or not, it does not work (i.e. ld reported cannot find -lthostmduserapi)

How ever, I managed to compile it by doing the following:

1) rename thostmduserapi.so to libthostmduserapi.so
2) add the following into implementation section:
{$linklib thostmduserapi.so}
{$linklib ThostMdIntf.a}
{$linklib stdc++}
{$linklib gcc_s}
{$linklib c}
3) Compile the project with LD_RUN_PATH=.

However, my last question is: How can I instruct FPC to look for thostmduserapi.so, NOT libthostmduserapi.so, i.e. WITHOUT the lib prefix?

I checked the ld man page, it said to put a colon prefix, to tell ld not to prepend "lib". I then did this:

{$linklib :thostmduserapi.so}

Unfortunately, ld still cannot find the library, however the error message changed:

/usr/bin/ld: cannot find thostmduserapi

while using {$linklib thostmduserapi.so}, the error was:

/usr/bin/ld: cannot find -lthostmduserapi

How to let ld look for library WITHOUT lib prefix?

Thanks!

[...] {$linklib :thostmduserapi.so} [...] How to let ld look for library WITHOUT lib prefix?

Have you tried to pass options to the linker using -k?

Mattias

Have you tried to pass options to the linker using -k?

That worked, thanks.

Xiangrong Fang wrote

Hi All, I need to use a C++ so file in FreePascal

AFAIK, you only can use C++ libraries in Pascal, if the functions for the mutual interface are "flat" C function (i. e. ANSI C functions not using any C++ classes). Of course, on top of this in both source codes the same ABI spec needs to be defined (e.g. "PASCAL" or "STDCALL").

-Michael

You know that he wrote this the following as well (directly after your quote ends)?

I have written a C wrapper for it, which successfully connected to Pascal.

He only has problems LINKING the library and here it does not matter whether the library is written in C or C++.

Regards,
Sven