[Lldb-commits] [PATCH] D134581: [lldb] Prevent re-adding a module that is already loaded

[Alvin Wong via Phabricator via lldb-commits]

alvinhochun created this revision.
alvinhochun added reviewers: labath, mstorsjo, clayborg, jingham.
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Herald added a project: LLDB.
Herald added a subscriber: lldb-commits.

LLDB preloads some dependent modules when creating the target. On
Windows, when the target is run and the dependent DLLs are actually
loaded by the process, `ProcessWindows::OnLoadDll` calls
`DynamicLoaderWindowsDYLD::OnLoadModule` which in turn calls
`Target::GetOrCreateModule` to try to load the DLL module. However, it
did not properly handle the case of getting an already-preloaded module,
and as a result any dependent DLLs preloaded by LLDB will end up being
duplicated in the target module list and causing some commands to return
repeated results (e.g. `target modules lookup`).

This issue does not seem to affect Linux, because the codepath it uses,
which goes through `DynamicLoader::FindModuleViaTarget`, has an
additional check to find existing modules before calling
`Target::GetOrCreateModule`.

This patch adds an early return to `Target::GetOrCreateModule` for when
it finds a pre-existing module already in the target module list to fix
the issue for Windows.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D134581

Files:
  lldb/source/Target/Target.cpp
  lldb/test/Shell/Target/Inputs/main.c
  lldb/test/Shell/Target/Inputs/shlib.c
  lldb/test/Shell/Target/dependent-modules-nodupe-windows.test


Index: lldb/test/Shell/Target/dependent-modules-nodupe-windows.test
===================================================================
--- /dev/null
+++ lldb/test/Shell/Target/dependent-modules-nodupe-windows.test
@@ -0,0 +1,20 @@
+# REQUIRES: system-windows
+
+# Checks that dependent modules preloaded by LLDB are not duplicated when the
+# process actually loads the DLL.
+
+# RUN: %clang_host -g0 -O0 -shared %S/Inputs/shlib.c -o %t.shlib.dll
+# RUN: %clang_host -g0 -O0 %S/Inputs/main.c %t.shlib.dll -o %t.main.exe
+# RUN: %lldb -b -o "#before" -o "target modules list" -o "b main" -o run \
+# RUN:       -o "#after" -o "target modules list" %t.main.exe | FileCheck %s
+
+# CHECK-LABEL: #before
+# CHECK-NEXT: target modules list
+# CHECK-NEXT: .main.exe
+# CHECK-NEXT: .shlib.dll
+
+# CHECK-LABEL: #after
+# CHECK-NEXT: target modules list
+# CHECK-NEXT: .main.exe
+# CHECK-NEXT: .shlib.dll
+# CHECK-NOT:  .shlib.dll
Index: lldb/test/Shell/Target/Inputs/shlib.c
===================================================================
--- /dev/null
+++ lldb/test/Shell/Target/Inputs/shlib.c
@@ -0,0 +1 @@
+__declspec(dllexport) void exportFunc(void) {}
Index: lldb/test/Shell/Target/Inputs/main.c
===================================================================
--- /dev/null
+++ lldb/test/Shell/Target/Inputs/main.c
@@ -0,0 +1,2 @@
+__declspec(dllimport) void exportFunc(void);
+int main() { exportFunc(); }
Index: lldb/source/Target/Target.cpp
===================================================================
--- lldb/source/Target/Target.cpp
+++ lldb/source/Target/Target.cpp
@@ -2134,6 +2134,13 @@
       }
     }
 
+    // If we found a pre-existing module, just return it.
+    if (module_sp && !did_create_module) {
+      if (error_ptr)
+        *error_ptr = error;
+      return module_sp;
+    }
+
     // We found a module that wasn't in our target list.  Let's make sure that
     // there wasn't an equivalent module in the list already, and if there was,
     // let's remove it.


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