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Date: Thu, 21 Jun 2012 14:12:46 -0600
From: Joe Lewis <joe@joe-lewis.com>
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To: modules-dev@httpd.apache.org
Subject: Re: How to compiling/link/use Apache module that uses shared library?
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On 6/21/12 1:40 PM, ohaya@cox.net wrote:
> ---- ohaya@cox.net wrote:
>> ---- Sorin Manolache<sorinm@gmail.com>  wrote:
>>> On 2012-06-21 19:47, ohaya@cox.net wrote:
>>>
>>>> I've tried using "-l" pointing directly to the .so, libobaccess.so, but when I do that, it says it can't find the .so:
>>>>
>>>> [root@apachemodule build-mod_headers]# ./compile-mod-headers.sh
>>>> /apps/httpd2222/build/libtool --silent --mode=compile gcc -prefer-pic   -DLINUX=2 -D_REENTRANT -D_GNU_SOURCE -g -O2 -pthread -I/apps/httpd2222/include  -I/apps/httpd2222/include   -I/apps/httpd2222/include   -c -o mod_headers.lo mod_headers.c&&  touch mod_headers.slo
>>>> /apps/httpd2222/build/libtool --silent --mode=link gcc -o mod_headers.la  -l/apps/netpoint/AccessServerSDK/oblix/lib/libobaccess.so -rpath /apps/httpd2222/modules -module -avoid-version    mod_headers.lo
>>>> /usr/bin/ld: cannot find -l/apps/netpoint/AccessServerSDK/oblix/lib/libobaccess.so
>>>> collect2: ld returned 1 exit status
>>>> apxs:Error: Command failed with rc=65536
>>> Try -lobaccess
>>>
>>> S
>>
>> Sorin,
>>
>> I was able to get Apache to start, kind of, using the apxs I posted, but adding LoadFile directives to the Apache httpd.conf, to load libobaccess.so.
>>
>> Now, when I run "apachectl -t", it says "OK", but when I try to actually start Apache, I get a segfault (see below).  The thing is, I have a bunch of printfs in almost every function in mod_headers.c, so I could see what functions are being called, and it looks like the segfault is occurring even before it gets to any of the code parts that I've tweaked (vs. original mod_headers.c):
>>
>>
>> [root@apachemodule build-mod_headers]# /apps/httpd2222/bin/apachectl -k start -X
>> mod_headers-jl V0.09 - start calling OAM API
>> In register_hooks
>> In create_headers_dir_config
>> In create_headers_dir_config
>> In header_cmd
>> In header_inout_cmd
>> In parse_format_tag
>> In parse_misc_string
>> In create_headers_dir_config
>> In header_cmd
>> In header_inout_cmd
>> In parse_format_tag
>> In parse_misc_string
>> In header_post_config
>>
>> I tried running strace, and got (the ending of the strace):
>>
>>
>> In register_hooks
>> In create_headers_dir_config
>> In create_headers_dir_config
>> In header_cmd
>> In header_inout_cmd
>> In parse_format_tag
>> In parse_misc_string
>> In create_headers_dir_config
>> In header_cmd
>> In header_inout_cmd
>> In parse_format_tag
>> In parse_misc_string
>> In header_post_config
>> rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
>> rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
>> rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
>> rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
>> rt_sigaction(SIGINT, {0x432cc0, [], SA_RESTORER, 0x351432e300}, {SIG_DFL}, 8) = 0
>> wait4(-1, [{WIFSIGNALED(s)&&  WTERMSIG(s) == SIGSEGV}], 0, NULL) = 11711
>> fstat(2, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 5), ...}) = 0
>> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2a983bf000
>> open("/usr/share/locale/locale.alias", O_RDONLY) = 3
>> fstat(3, {st_mode=S_IFREG|0644, st_size=2528, ...}) = 0
>> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2a983c0000
>> read(3, "# Locale name alias data base.\n#"..., 4096) = 2528
>> read(3, "", 4096)                       = 0
>> close(3)                                = 0
>> munmap(0x2a983c0000, 4096)              = 0
>> open("/usr/share/locale/en_US.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
>> open("/usr/share/locale/en_US.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
>> open("/usr/share/locale/en_US/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
>> open("/usr/share/locale/en.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
>> open("/usr/share/locale/en.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
>> open("/usr/share/locale/en/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
>> write(2, "/apps/httpd2222/bin/apachectl: l"..., 83/apps/httpd2222/bin/apachectl: line 78: 11711 Segmentation fault      $HTTPD $ARGV
>> ) = 83
>> rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
>> --- SIGCHLD (Child exited) @ 0 (0) ---
>> wait4(-1, 0x7fbfffed64, WNOHANG, NULL)  = -1 ECHILD (No child processes)
>> rt_sigreturn(0xffffffffffffffff)        = 0
>> rt_sigaction(SIGINT, {SIG_DFL}, {0x432cc0, [], SA_RESTORER, 0x351432e300}, 8) = 0
>> rt_sigprocmask(SIG_BLOCK, NULL, [], 8)  = 0
>> read(255, "\nexit $ERROR\n\n", 3420)    = 14
>> rt_sigprocmask(SIG_BLOCK, NULL, [], 8)  = 0
>> rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
>> exit_group(139)                         = ?
>>
>>
>> I'll try to do the apxs with -lobccess and post back...
>>
>> Jim
>
> Hi,
>
> It looks like just including the .so in the apxs command is enough to cause the segfault, even if I remove all references to the functions in the .so from my module code.
>
> Is there something else I need to do when using my module that uses "external" .so files?
>
> Jim

You may need to ensure the .so is in your ldconfig paths.  If you do an 
"ldconfig -p" and grep for your module, it should show up.  
Additionally, on your compile, split your -l/-L into two parts :

-L/apps/netpoint/AccessServerSDK/oblix/lib/ -llibobaccess

See if that behaves any differently.

Joe
--
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