Question about dlopen load ordering

[Caslyn Tonelli]

Hello,

I’m hoping someone could help clarify the load ordering semantics of
glibc’s dlopen for a specific scenario:

multiple-foo-deps.so has the following DT_NEEDEDs in this order:

  - libfoo-v1.so where foo() returns 2

  - libfoo-v2.so where foo() returns 7

If I perform the following steps:
1. dlopen(“libfoo-v2.so”, RTLD_NOW | RTLD_LOCAL);
2. dlopen(“multiple-foo-deps.so”, RTLD_NOW | RTLD_LOCAL);

What would be the value of the resolved `foo()` from “multiple-foo-deps.so
”?

Based on POSIX documentation, I would expect the value to be 7 since “
libfoo-v2.so” was already loaded. However, my tests are showing that the
dependency order is prioritized and the foo symbol is resolved from “
libfoo-v1.so”. Is that right? Would someone be able to explain the
reasoning around this?

Let me know if I can clarify anything or provide a reproducer.

Thanks!
Caslyn