[dlfcn] E: Add tests for ctors/dtors and DT_RUNPATH

[esaurez]

Summary

Add a new test suite dlfcn-init-runpath-c that exercises three System V ABI capabilities of the Nanvix dynamic loader:

1. .init_array constructor invocation on dlopen
2. .fini_array destructor invocation on dlclose
3. DT_RUNPATH-driven DT_NEEDED resolution

The companion loader PR that implements these features is nanvix/nanvix#2473.

Test design

• libctor.so — has __attribute__((constructor)) writing a sentinel to a library-local global, and __attribute__((destructor)) writing a different sentinel to the test program's extern volatile int g_dtor_ran (exported by -rdynamic). The destructor witness survives the library being unloaded because the global lives in the main executable.
• libparent.so — linked with -lchild -Wl,--enable-new-dtags,-rpath,lib/subdir. The linker emits DT_NEEDED libchild.so plus DT_RUNPATH lib/subdir.
• libchild.so — staged into lib/subdir/ only (never lib/) via SUITE_RAMFS_LIBS. The only way the loader can find it is by honouring libparent's DT_RUNPATH.

Hooks

File	Change
src/dlfcn-init-runpath-c/{Makefile,main.c,libs/*}	New suite
Makefile, src/Makefile	Register dlfcn-init-runpath-c in SUITES
.nanvix/z.py	Register suite in ALL_SUITES, STANDALONE_ONLY_SUITES, and SUITE_RAMFS_LIBS (the latter stages libchild.so under lib/subdir/)

Validation

Run on a standalone Nanvix VM with the loader changes from nanvix/nanvix#2473:

RUN  dlfcn-init-runpath-c...
=== dlfcn init_array + DT_RUNPATH tests ===
  PASS: init_array fires on dlopen
  PASS: fini_array fires on dlclose
  PASS: DT_RUNPATH dependency search

3 passed, 0 failed
OK   dlfcn-init-runpath-c
        *** POSIX tests PASSED ***

All 15 testable suites pass (the new suite plus the 14 pre-existing ones).

ELF metadata sanity check

$ readelf -d build/libparent.so | head -4
 0x00000001 (NEEDED)                     Shared library: [libchild.so]
 0x0000001d (RUNPATH)                    Library runpath: [lib/subdir]

$ readelf -d build/libctor.so | grep -E "INIT_ARRAY|FINI_ARRAY"
 0x00000019 (INIT_ARRAY)                 0x1188
 0x0000001b (INIT_ARRAYSZ)               4 (bytes)
 0x0000001a (FINI_ARRAY)                 0x118c
 0x0000001c (FINI_ARRAYSZ)               4 (bytes)

This PR is unlinked-but-meaningful without the loader change: the test would fail with "destructor sentinel not set" / "DT_RUNPATH dependency search" / "constructor sentinel not set" on an unpatched loader.

[Copilot]

Pull request overview

Adds a new POSIX test suite that validates Nanvix’s dynamic loader behavior around ELF constructors/destructors and DT_RUNPATH resolution, integrating it into the build and standalone test harness wiring.

Changes:

• Introduces new suite dlfcn-init-runpath-c that checks .init_array on dlopen, .fini_array on dlclose, and DT_RUNPATH-driven DT_NEEDED lookup.
• Registers the suite in the build system (Makefile, src/Makefile) so it’s built alongside existing suites.
• Hooks the suite into .nanvix/z.py standalone execution and ramfs library staging (including staging libchild.so under lib/subdir/).

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/Makefile	Adds dlfcn-init-runpath-c to the full suite build list.
src/dlfcn-init-runpath-c/Makefile	Builds the new test ELF and its companion shared libraries (libctor.so, libparent.so, libchild.so).
src/dlfcn-init-runpath-c/main.c	Implements the three runtime checks for ctor/dtor execution and DT_RUNPATH dependency search.
src/dlfcn-init-runpath-c/libs/subdir/child.c	Defines libchild.so dependency target for DT_NEEDED resolution via DT_RUNPATH.
src/dlfcn-init-runpath-c/libs/parent.c	Defines libparent.so that declares DT_NEEDED on libchild.so.
src/dlfcn-init-runpath-c/libs/ctor.c	Defines libctor.so with constructor/destructor sentinels used by the test.
Makefile	Adds dlfcn-init-runpath-c to the Docker/host build suite list.
.nanvix/z.py	Registers suite and stages required shared libraries into the ramfs (including subdir placement for DT_RUNPATH).

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