From f7a628267af575bdbfe478c11ceef875087252b8 Mon Sep 17 00:00:00 2001
From: Marco Casaroli <marco.casaroli@gmail.com>
Date: Mon, 3 Aug 2026 12:26:13 +0200
Subject: [PATCH] examples/sotest: Check that a library can be opened twice.

dlopen() of an already loaded library used to fail, so nothing exercised
what happens when two callers hold the same object.

Open the library a second time, check the same handle comes back, close
one of the two and check the library is still usable through the other.

Needs the counterpart change in nuttx; without it the second dlopen()
returns NULL and this reports it.

Assisted-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com>
---
 examples/sotest/main/sotest_main.c | 37 ++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/examples/sotest/main/sotest_main.c b/examples/sotest/main/sotest_main.c
index 6b2417ddb21..94b7eab8180 100644
--- a/examples/sotest/main/sotest_main.c
+++ b/examples/sotest/main/sotest_main.c
@@ -130,6 +130,7 @@ int main(int argc, FAR char *argv[])
   FAR void *handle1;
 #endif
   FAR void *handle2;
+  FAR void *handle3;
   CODE void (*testfunc)(FAR const char *msg);
   FAR const char *msg;
   int ret;
@@ -326,6 +327,42 @@ int main(int argc, FAR char *argv[])
 
   testfunc(msg);
 
+  /* Open the same library again.  dlopen() must return the object that is
+   * already loaded, and closing one of the two handles must leave the
+   * other usable.
+   */
+
+  handle3 = dlopen(sotest_path, RTLD_NOW | RTLD_LOCAL);
+  if (handle3 == NULL)
+    {
+      fprintf(stderr, "ERROR: dlopen(%s) failed on an already loaded "
+                      "library\n", sotest_path);
+      exit(EXIT_FAILURE);
+    }
+
+  if (handle3 != handle2)
+    {
+      fprintf(stderr, "ERROR: dlopen() returned %p for a library already "
+                      "loaded at %p\n", handle3, handle2);
+      exit(EXIT_FAILURE);
+    }
+
+  ret = dlclose(handle3);
+  if (ret != 0)
+    {
+      fprintf(stderr, "ERROR: dlclose(handle3) failed: %d\n", ret);
+      exit(EXIT_FAILURE);
+    }
+
+  testfunc = (CODE void (*)(FAR const char *))dlsym(handle2, "testfunc1");
+  if (testfunc == NULL)
+    {
+      fprintf(stderr, "ERROR: closing one handle unloaded the library\n");
+      exit(EXIT_FAILURE);
+    }
+
+  testfunc(msg);
+
 #if CONFIG_LIBC_ELF_MAXDEPEND > 0
   /* This should fail because the second shared library depends on
    * the first.