ld.so: add RTLD_LOCAL, RTLD_DEEPBIND notes + example

1 files changed, 40 insertions, 0 deletions

diff --git a/src/development/ldso/deepbind/main.c b/src/development/ldso/deepbind/main.c
new file mode 100644
index 0000000..6d93520
--- /dev/null
+++ b/src/development/ldso/deepbind/main.c
@@ -0,0 +1,40 @@
+#include <dlfcn.h>
+#include <stdio.h>
+
+int main() {
+  puts("-- deep --");
+  // Load library into its own LOCAL scope with DEEPBINDING, meaning that
+  // symbols will first resolve to the library + its dependencies first before
+  // considering global symbols.
+  void* h1 = dlopen("./libdeep.so", RTLD_LAZY | RTLD_LOCAL | RTLD_DEEPBIND);
+  if (h1) {
+    // Lookup symbol in the libraries LOCAL scope (library + its own
+    // dependencies).
+    void (*test_fn)() = dlsym(h1, "test");
+    test_fn();
+
+    // Lookup non-existing symbol in the libraries LOCAL scope (library + its
+    // own dependencies).
+    (void)dlsym(h1, "libdeep_main");
+  }
+
+  puts("-- nodp --");
+  // Load library into its own LOCAL scope.
+  void* h2 = dlopen("./libnodp.so", RTLD_LOCAL | RTLD_LAZY);
+  if (h2) {
+    // Lookup symbol in the libraries LOCAL scope (library + its own
+    // dependencies).
+    void (*test_fn)() = dlsym(h2, "test");
+    test_fn();
+
+    // Lookup non-existing symbol in the libraries LOCAL scope (library + its
+    // own dependencies).
+    (void)dlsym(h2, "libnodp_main");
+  }
+
+  puts("-- main --");
+  // Lookup non-existing symbol in the GLOBAL scope.
+  (void)dlsym(RTLD_DEFAULT, "default_main");
+
+  return 0;
+}