[asterisk-dev] Problems with custom C-file: undefined reference

Mon Dec 12 04:40:12 CST 2016

Thank you for this simple solution, it solved the last problem.

Another issue arised: Before, system.c was in the main/ directory and used
the project wide exports file to export its functions, now it's in
channels/ where apparantly doesn't exist such a file.
I created *system.exports.in <http://system.exports.in>* in channels/ to
export the functions but the Asterisk build system does not automatically
generate the *system.exports* file and manually creating it doesn't work
either.

*system.h*
void ast_system_get_address(struct ast_sockaddr *us);

*system.c*
#include "asterisk/system.h"

void ast_system_get_address(struct ast_sockaddr *us)
{
   ...
}

*chan_sip.c*
#include "asterisk/system.h"

ast_system_get_address(us);

2016-12-09 18:42 GMT+01:00 Corey Farrell <git at cfware.com>:

> I'm not sure what you're trying to accomplish but this is not the approach
> I'd take for expanding chan_sip.  My advice is to simply put your system.c
> into channels/sip.  This will automatically link it into the binary
> chan_sip module, but allow you to keep your source code in a separate
> file.  I believe MODULEINFO (for any added dependencies) and possibly a
> call to your init/cleanup would be the only changes you'd need to make in
> chan_sip.c.  All non-static symbols in chan_sip.c and channels/sip/*.c are
> available across all sources of chan_sip.so without needing
> chan_sip.exports.in or AST_MODFLAG_GLOBAL_SYMBOLS.
>
> The only exception is if you need to call chan_sip functions from another
> existing module, then you will have to export the symbols.  To do this you
> have to tell the linker (via chan_sip.exports.in) and you have to tell
> the module loader.  AST_MODULE_INFO at the very end of chan_sip.c would
> need AST_MODFLAG_GLOBAL_SYMBOLS so the module loader knows to share the
> globals:
>
> AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_GLOBAL_SYMBOLS
> | AST_MODFLAG_LOAD_ORDER, "Session Initiation Protocol (SIP)",
>
>
>
> On Fri, Dec 9, 2016 at 10:50 AM, Julian Fleischhauer <
> julian.fleischhauer at stud.uni-due.de> wrote:
>
>> I could resolve the XML and pcap issues, but still have problems
>> concerning "sip_get_header()". I don't want to rename the function since
>> it's a frequently used function in chan_sip.c, I therefore defined an .
>> exports.in file. I don't know if Mr. Michelson understood me correctly,
>> but I think chan_sip.c exports "sip_get_header()" (doesn't it?) so I
>> modified *chan_sip.exports.in <http://chan_sip.exports.in>* so it looks
>> like
>> {
>> global:
>> LINKER_SYMBOL_PREFIXsip_get_header;            // I also tried
>> LINKER_SYMBOL_PREFIXsip_*;
>> LINKER_SYMBOL_PREFIX_IO_stdin_used;
>> local:
>> *;
>> };
>> But it doesn't work. I did the same with *system.exports.in
>> <http://system.exports.in>*, without success.
>>
>>
>> Sorry for the badly formatted last mail. I will post the updated file
>> structure again below.
>>
>> *sip.h*
>> const char *sip_get_header(const struct sip_request *req, const char
>> *name);
>>
>> *system.h*
>> #include "asterisk/netsock2.h"
>>
>> void ast_some_function(struct sip_pvt *p, struct ast_sockaddr *addr);
>>
>> *system.c*
>> #include "asterisk/system.h"
>> #include "asterisk/sip.h"
>>
>> void ast_some_function(struct sip_pvt *p, struct ast_sockaddr *addr)
>> {
>>    ast_copy_string(touser, sip_get_header(req, "To"),
>> strlen(sip_get_header(req, "To")) + 1);
>> }
>>
>> *chan_sip.c*
>> #include "asterisk/system.h"
>> #include "asterisk/sip.h"
>>
>> ast_some_function(p, addr);
>>
>>
>> Best regards,
>> Julian Fleischhauer
>>
>> 2016-12-06 18:35 GMT+01:00 Mark Michelson <mmichelson at digium.com>:
>>
>>> On 12/05/2016 04:53 PM, Julian Fleischhauer wrote:
>>>
>>>> Hey all,
>>>>
>>>> I have a problem using a custom C-file. The error ouput received when
>>>> compiling is given below.
>>>>
>>>> error output
>>>> .../system.c:1330: undefined reference to `XML_ParserCreate'
>>>> ...
>>>> .../system.c:1465: undefined reference to `sip_get_header'
>>>> ...
>>>> .../system.c:1608: undefined reference to `pcap_lookupnet'
>>>> ...
>>>>
>>>>
>>>> Before, I had all code in chan_sip.c. I want to transfer the code into
>>>> a separate file (system.c) now. The dependencies given below MODULEINFO are
>>>> customly set and worked fine when used in chan_sip.c. Can anyone figure out
>>>> if something else has to be added somewhere? The code is quoted below:
>>>>
>>>> sip.h
>>>> const char *sip_get_header(const struct sip_request *req, const char
>>>> *name);
>>>>
>>>> system.h
>>>> #include "asterisk/netsock2.h"
>>>>
>>>> void ast_some_function(struct sip_pvt *p, struct ast_sockaddr *addr);
>>>>
>>>> system.c
>>>> /*** MODULEINFO
>>>>      <depend>sqlite3</depend>
>>>>      <depend>expat</depend>
>>>>      <depend>pcap</depend>
>>>>     <support_level>extended</support_level>
>>>> ***/
>>>>
>>>> #include "asterisk/system.h"
>>>> #include "asterisk/sip.h"
>>>>
>>>> void ast_some_function(struct sip_pvt *p, struct ast_sockaddr *addr)
>>>> {
>>>>     xmlParser = XML_ParserCreate(NULL);
>>>>    ...
>>>>    ast_copy_string(touser, sip_get_header(req, "To"),
>>>> strlen(sip_get_header(req,       "To"))+1);
>>>>    ...
>>>>    pcap_lookupnet(pcapDev, &netp, &maskp, errbuf);
>>>> }
>>>>
>>>> chan_sip.c
>>>> #include "asterisk/system.h"
>>>> #include "asterisk/sip.h"
>>>>
>>>> ast_some_function(p, addr);
>>>>
>>>>
>>>> Thank you for any help!
>>>>
>>>> Regards,
>>>> Juliannn
>>>>
>>>> I can explain why sip_get_header() is causing a problem. In order for
>>> functions to be callable from other modules, they need to be explicitly
>>> exported. This is why you'll see files like res/res_agi.exports.in,
>>> which define functions that can be called globally from that module. You
>>> have a couple of options here:
>>>
>>> * Define a .exports.in file for your system.c file that exports the
>>> sip_get_header() function.
>>> * Change "sip_get_header()" to "ast_sip_get_header()". Assuming that
>>> system.c is in the main/ directory, there is a project-wide exports file
>>> that makes it so any function starting with "ast" can be called externally.
>>>
>>> Regarding the XML and pcap issues, the issues are either that
>>> * You're not #including the necessary files.
>>> * The libraries are not being linked during compilation.
>>>
>>> The first problem is easy to fix: just #include the right files :). The
>>> second problem is a bit more tricky because you'll need to dig into
>>> Makefiles and try to figure out how libraries get linked when Asterisk is
>>> built.
>>>
>>>
>>> --
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>>>
>>
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>
>
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