[clue-tech] Broke Apache by upgrading PCRE

[Matt Gushee]

William wrote:

> httpd was updated with yum and was working fine until the PCRE upgrade.
> PCRE was upgraded from source (ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/) to the
> latest version.

Do you know what your Apache uses PCRE for? Mine doesn't, and neither do 
   any of the modules I have installed--at least not directly.

> Error message when executing "service httpd start" (as root):
> =============================================================
> Starting httpd: /usr/sbin/httpd: symbol lookup error: /usr/lib/libpcreposix.so.0: undefined
> symbol: pcre_compile2     [FAILED]

Let's see ... you probably know this, but just for the sake of 
thoroughness, "symbol lookup error" means that *something* is trying to 
call a function that is expected to be provided by an external library, 
but for some reason that function is unavailable. From the above error 
message, it appears that some function in libpcreposix is attempting to 
call pcre_compile2. Now, what library would provide that?

Well, time to play "Grep-the-Headers." On my system:

   $ grep pcre_compile /usr/include/*.h
   /usr/include/pcre.h:extern pcre *pcre_compile(const char *, int, ...

So there is a 'pcre_compile' function defined in libpcre. I'd be willing 
to bet that (1) some version of libpcre has a 'pcre_compile2' function, 
but not the one I have, and (2) if you run the above 'grep' command, you 
will also find 'pcre_compile' but not 'pcre_compile2'.

So first of all I would check the timestamps on the relevant libraries:

   $ ls -l /path/to/libs/libpcre*

libpcre.so.* and libpcreposix.so.* should have been created at the same 
time. If they weren't, that is presumably because you compiled/installed 
one of them but not the other. In that case you would need to rebuild 
PCRE, this time making sure that both libs get built ... maybe there's a 
configure option, '--with-posix' or something like that?

On the other hand, if the two libraries were created at the same time, 
it could be a bug in PCRE ... but I wouldn't rule out a configuration 
problem just yet.

Two things that come to mind are:

Did you remember to run 'ldconfig' after you installed PCRE?

Is it possible you have another version of either libpcre or 
libpcreposix that you installed once and forgot about ... in 
/usr/local/lib, for example? Check all the paths listed in 
/etc/ld.so.conf; and if you have $LD_LIBRARY_PATH defined, check those 
paths too.

Hope this helps.

--
Matt Gushee
Englewood, CO, USA

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