GH-128469: warn when libpython was loaded from outside the build directory

Signed-off-by: Filipe Laíns <[email protected]

Author: FFY00

Modules/getpath.py

@@ -783,6 +783,19 @@ def search_up(prefix, *landmarks, test=isfile):
     base_exec_prefix = config.get('base_exec_prefix') or EXEC_PREFIX or base_prefix
 
 
+# ******************************************************************************
+# MISC. RUNTIME WARNINGS
+# ******************************************************************************
+
+# When running Python from the build directory, if libpython is dynamically
+# linked, the wrong library might be loaded.
+if build_prefix and not build_prefix.startswith(dirname(abspath(library))):
+    msg = f'The runtime library has been loaded from outside the build directory ({library})!'
+    if os_name == 'posix':
+        msg += ' Consider setting LD_LIBRARY_PATH=. to force it to be loaded from the build directory.'
+    warn(msg)
+
+
 # ******************************************************************************
 # SET pythonpath FROM _PTH FILE
 # ******************************************************************************