[lldb][test] Prevent infinite loop while looking for use_lldb_suite_root.py.

Several scripts (two copies of use_lldb_suite.py, and an __init__.py) look for use_lldb_suite_root.py by checking parent directories. If for some reason it doesn't exist, it keeps checking parent directories until it finds it.

However, this only breaks when the parent directory is None, but at least on Linux, dirname('/') == '/', so this will never be None.

This changes the lookup to stop if the dirname(lldb_root) is unchanged. This was previously fixed in 67f6d842fa, but only in one copy of this script.

Additionally, this makes the failure mode more visible -- if the root is not found, it complains loudly instead of silently failing, and having later modules that need lldb_root fail.

Differential Revision: https://reviews.llvm.org/D83840

lldb/packages/Python/lldbsuite/__init__.py

@@ -8,14 +8,14 @@ import sys
 def find_lldb_root():
     lldb_root = os.path.dirname(inspect.getfile(inspect.currentframe()))
     while True:
-        lldb_root = os.path.dirname(lldb_root)
-        if lldb_root is None:
-            return None
+        parent = os.path.dirname(lldb_root)
+        if parent == lldb_root: # dirname('/') == '/'
+            raise Exception("use_lldb_suite_root.py not found")
+        lldb_root = parent
 
         test_path = os.path.join(lldb_root, "use_lldb_suite_root.py")
         if os.path.isfile(test_path):
             return lldb_root
-    return None
 
 # lldbsuite.lldb_root refers to the root of the git/svn source checkout
 lldb_root = find_lldb_root()

lldb/scripts/use_lldb_suite.py

@@ -8,20 +8,18 @@ def find_lldb_root():
     while True:
         parent = os.path.dirname(lldb_root)
         if parent == lldb_root: # dirname('/') == '/'
-            break
+            raise Exception("use_lldb_suite_root.py not found")
         lldb_root = parent
 
         test_path = os.path.join(lldb_root, "use_lldb_suite_root.py")
         if os.path.isfile(test_path):
             return lldb_root
-    return None
 
 lldb_root = find_lldb_root()
-if lldb_root is not None:
-    import imp
-    fp, pathname, desc = imp.find_module("use_lldb_suite_root", [lldb_root])
-    try:
-        imp.load_module("use_lldb_suite_root", fp, pathname, desc)
-    finally:
-        if fp:
-            fp.close()
+import imp
+fp, pathname, desc = imp.find_module("use_lldb_suite_root", [lldb_root])
+try:
+    imp.load_module("use_lldb_suite_root", fp, pathname, desc)
+finally:
+    if fp:
+        fp.close()

lldb/test/API/use_lldb_suite.py

@@ -8,21 +8,21 @@ def find_lldb_root():
         os.path.abspath(inspect.getfile(inspect.currentframe()))
     )
     while True:
-        lldb_root = os.path.dirname(lldb_root)
-        if lldb_root is None:
-            return None
+        parent = os.path.dirname(lldb_root)
+        if parent == lldb_root: # dirname('/') == '/'
+            raise Exception("use_lldb_suite_root.py not found")
+        lldb_root = parent
 
         test_path = os.path.join(lldb_root, "use_lldb_suite_root.py")
         if os.path.isfile(test_path):
             return lldb_root
-    return None
 
 lldb_root = find_lldb_root()
-if lldb_root is not None:
-    import imp
-    fp, pathname, desc = imp.find_module("use_lldb_suite_root", [lldb_root])
-    try:
-        imp.load_module("use_lldb_suite_root", fp, pathname, desc)
-    finally:
-        if fp:
-            fp.close()
+
+import imp
+fp, pathname, desc = imp.find_module("use_lldb_suite_root", [lldb_root])
+try:
+    imp.load_module("use_lldb_suite_root", fp, pathname, desc)
+finally:
+    if fp:
+        fp.close()