From 6aa919990d6f0f241e9e5584c78abb3b16ce6b25 Mon Sep 17 00:00:00 2001
From: Rolf Madsen <rolf_madsen@keysight.com>
Date: Tue, 9 Jun 2026 13:53:49 +0200
Subject: [PATCH] Fixed loading vcredist when vcredist is not installed. (#221)

Bumped git version to 3.2.2
---
 .gitversion                 |  2 +-
 OpenTap.Python/SharedLib.cs | 32 ++++++++++++++++++++++++++++++--
 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/.gitversion b/.gitversion
index b440777..1aebe2b 100644
--- a/.gitversion
+++ b/.gitversion
@@ -3,7 +3,7 @@
 
 # This is the version number that will be used. Prerelease numbers are calculated by 
 # counting git commits since the last change in this value.
-version = 3.2.1
+version = 3.2.2
 
 # A version is determined to be a "beta" prerelease if it originates from the default branch
 # The default branch is the first branch that matches the following regular expession.
diff --git a/OpenTap.Python/SharedLib.cs b/OpenTap.Python/SharedLib.cs
index be72015..b9fc767 100644
--- a/OpenTap.Python/SharedLib.cs
+++ b/OpenTap.Python/SharedLib.cs
@@ -62,9 +62,13 @@ static void clearError()
     }
 
 
-    [DllImport("kernel32.dll")]
+    [DllImport("kernel32.dll", SetLastError = true)]
     static extern IntPtr LoadLibrary(string dllToLoad);
     
+    const uint LOAD_WITH_ALTERED_SEARCH_PATH = 0x00000008;
+    [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
+    static extern IntPtr LoadLibraryEx(string lpFileName, IntPtr hFile, uint dwFlags);
+    
     [DllImport("kernel32", CharSet = CharSet.Ansi, SetLastError = true)]
     static extern IntPtr GetProcAddress(IntPtr hModule, string procName);
 
@@ -157,13 +161,37 @@ public IntPtr GetSymbol(string symbolName)
         return libdl.dlsym(lib, symbolName);
     }
 
+    private static TraceSource log = Log.CreateSource("Python");
     public static SharedLib Load(string name)
     {
         clearError();
-        IntPtr p = load(name);
+        IntPtr p;
+        if (IsWin32)
+        {
+            p = LoadLibrary(name);
+            if (p == IntPtr.Zero)
+            {
+                // if vcredist is not installed, we can usually find it right next to python dll.
+                // If LoadLibraryEx is used this way, it will try to load the DLL with alternative search strategy.
+                //   this usually resolves in it finding vcredist dll right next ot the python dll and then successfully loading.
+                p = LoadLibraryEx(name, IntPtr.Zero, LOAD_WITH_ALTERED_SEARCH_PATH);
+                if (p == IntPtr.Zero)
+                {
+                    int err = Marshal.GetLastWin32Error();
+                    var ex = new Win32Exception(err); // gives readable message
+                    log.Error($"Unable to load {name}: {ex.Message}");
+                }
+            }
+        }
+        else
+        {
+            p = load(name);
+        }
+
         if (p == IntPtr.Zero)
         {
             checkError();
+            
             return null;
         }
         return new SharedLib(p);