Net-SNMP 5.4.1.pre3 - Need a fix for AIX support

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Hello all,

I tested 5.4.1.pre3 on AIX. This version still needs a fix for dlopen use on
AIX. (AIX dlopen does not support lazy loading. When dlopen is called for a
Net-SNMP library, there cannot be unresolved symbols. Otherwise, dlopen
fails.)

Followings are the build order of Net-SNMP library files.

1. libnetsnmp.so (self-contained)
2. libnetsnmpagent.so (import symbols from 1 and 3) (linked with 1)
3. libnetsnmphelpers.so (import symbols from 1 and 2) (linked with 1 and 2)
4. libnetsnmpmibs.so (import symbols from 1, 2 and 3) (linked with 1, 2 and
3)

The way it builds libs in this version is one-pass build linking with libs
built before. You build 1 first. You build 2 linking with 1 and build 3
linking with 1 and 2 (and so on). Therefore, 2 ( libnetsnmpagent.so) must be
linked with 3 which is missing here. Because of this, 2 has undefined
symbols imported from 3 which results in dlopen failure. However, if we
arrange the order of dlopen (i.e., do dlopen 2 later than 3), then it works
because all symbols can be resolved.

I think followings must be considered for the next version.

A. Make 2 (libnetsnmpagent.so) be linked with 3 (libnetsnmphelpers.so). It
requires the second-pass build.
B. If option A is not feasible, README.aix should include the explanation
about dlopen orders. It should state that 2 ( libnetsnmpagent.so) must be
dlopened later than others.

It seems that restricting dlopen orders is not that good idea. Do you think
it is feasible to incorporate option A in your libtool?

Sincerely,

Sukwoo Kang

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Hello all,<br><br>I tested 5.4.1.pre3 on AIX. This version still needs a fix for dlopen use on AIX. (AIX dlopen does not support lazy loading. When dlopen is called for a Net-SNMP library, there cannot be unresolved symbols. Otherwise, dlopen fails.)
<br><br>Followings are the build order of Net-SNMP library files.<br><br>1. libnetsnmp.so (self-contained)<br>2. libnetsnmpagent.so (import symbols from 1 and 3) (linked with 1) <br>3. libnetsnmphelpers.so (import symbols from 1 and 2) (linked with 1 and 2)
<br>4. libnetsnmpmibs.so (import symbols from 1, 2 and 3) (linked with 1, 2 and 3)<br><br>The way it builds libs in this version is one-pass build linking with libs built before. You build 1 first. You build 2 linking with 1 and build 3 linking with 1 and 2 (and so on). Therefore, 2 (
libnetsnmpagent.so) must be linked with 3 which is missing here. Because of this, 2 has undefined symbols imported from 3 which results in dlopen failure. However, if we arrange the order of dlopen (i.e., do dlopen 2 later than 3), then it works because all symbols can be resolved.
<br><br>I think followings must be considered for the next version.<br><br>A. Make 2 (libnetsnmpagent.so) be linked with 3 (libnetsnmphelpers.so). It requires the second-pass build.<br>B. If option A is not feasible, README.aix
should include the explanation about dlopen orders. It should state that 2 ( libnetsnmpagent.so) must be dlopened later than others.<br><br>It seems that restricting dlopen orders is not that good idea. Do you think it is feasible to incorporate option A in your libtool?
<br><br>Sincerely,<br><br>Sukwoo Kang <br>

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