问题
A compulsion of LD_PRELOAD on HP platform only and not on other unix flavors (AIX,Linux, and Solaris).
I built Perl Module XML::LibXML::Common on all of Unix flavors.I had to specifically do LD_PRELOAD for libcl.2 library on HP Platform only. While on other unix platforms nothing as such was required.
Is this an OS behaviour or something really missing in HP loader/compiler?
I was running a perl script which simply creates a new object of "XML::LibXML::SAX"
use XML::LibXML::SAX;
$x = XML::LibXML::SAX->new();
and it complained for
Can't load 'site_perl/5.8.8/PA-RISC2.0-thread-multi/auto/XML/LibXML/Common/Common.sl' for module XML::LibXML::Common: Exec format error
and when i do the LD_PRELOAD for libcl.2 the error goes away and the Perl is built for a multi threaded support.
回答1:
I think you are asking why you have to use it. If you are running Perl multi-threaded one of the libraries you are calling is getting loaded before libc and it is likely single threaded. As part of its dependency processing, it is attempting to load a multi-threaded library in your environment. By using LD_PRELOAD I think you are using the principle of library interposition to force that library to load prior to loading the unsafe library. The notion of interposition is a complex one and you might gain some benefit from the following link:
Excerpt:
To use library interposition, you need to create a special shared library and set the LD_PRELOAD environment variable. When LD_PRELOAD is set, the dynamic linker will use the specified library before any other when it searches for shared libraries.
回答2:
Your question isn't clear...why did you have to use LD_PRELOAD?
Is it because HP-UX uses SHLIB_PATH instead of LD_LIBRARY_PATH, so you were setting the wrong environment variable?
It has other spellings on other platforms, too - Solaris and Linux happen to share much the same set of env. vars. MacOS X uses DYLIB_LIBRARY_PATH; AIX uses use LIBPATH, I believe.
回答3:
Though this is an old subject, I'm seeing something similar on HP-UX right now. In my case, it's not Perl, but while building Python's sqlite3 binding, dynamic loading of /usr/lib/libcl.2 is failing.
I've run the configure script with --with-libs='-lcl'. Though linking it to the binary and using LD_PRELOAD is not the same, both changes when /usr/lib/libcl.2 is loaded. Since it solved mine, try that.
回答4:
I'm not sure if this is relevant, but it probably is. THe Perl included with HP-UX is not the standard Perl but is a copy of ActiveState Perl - along with whatever strangeness that might include. If you find Perl acting strangely on HP-UX in contrast to every other environment - check whether ActiveState Perl is at fault.
来源：https://stackoverflow.com/questions/752573/why-do-i-have-to-use-ld-preload-for-libcl-2-to-use-xmllibxmlcommon-on-hp-ux