diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index 389c5eeb5d..636307bedf 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -84,7 +84,7 @@ static ssize_t ga_pipe_read_str(int fd[2], char **str)
         *str = g_realloc(*str, len + n + 1);
         memcpy(*str + len, buf, n);
         len += n;
-        *str[len] = '\0';
+        (*str)[len] = '\0';
     }
     close(fd[0]);
     fd[0] = -1;
diff --git a/qga/commands-windows-ssh.c b/qga/commands-windows-ssh.c
index 6a642e3ba8..df45c17b75 100644
--- a/qga/commands-windows-ssh.c
+++ b/qga/commands-windows-ssh.c
@@ -377,7 +377,7 @@ error:
 static bool set_file_permissions(PWindowsUserInfo userInfo, Error **errp)
 {
     PACL pACL = NULL;
-    PSID userPSID;
+    PSID userPSID = NULL;
 
     /* Creates the access control structure */
     if (!create_acl(userInfo, &pACL, errp)) {
diff --git a/qga/vss-win32/install.cpp b/qga/vss-win32/install.cpp
index 84944133f7..5cea5bcf74 100644
--- a/qga/vss-win32/install.cpp
+++ b/qga/vss-win32/install.cpp
@@ -39,7 +39,7 @@ const GUID CLSID_WbemLocator = { 0x4590f811, 0x1d3a, 0x11d0,
 const GUID IID_IWbemLocator = { 0xdc12a687, 0x737f, 0x11cf,
     {0x88, 0x4d, 0x00, 0xaa, 0x00, 0x4b, 0x2e, 0x24} };
 
-void errmsg(DWORD err, const char *text)
+static void errmsg(DWORD err, const char *text)
 {
     /*
      * `text' contains function call statement when errmsg is called via chk().
@@ -242,6 +242,7 @@ out:
 }
 
 /* Unregister this module from COM+ Applications Catalog */
+STDAPI COMUnregister(void);
 STDAPI COMUnregister(void)
 {
     qga_debug_begin;
@@ -256,6 +257,7 @@ out:
 }
 
 /* Register this module to COM+ Applications Catalog */
+STDAPI COMRegister(void);
 STDAPI COMRegister(void)
 {
     qga_debug_begin;
@@ -380,11 +382,13 @@ out:
     return hr;
 }
 
+STDAPI_(void) CALLBACK DLLCOMRegister(HWND, HINSTANCE, LPSTR, int);
 STDAPI_(void) CALLBACK DLLCOMRegister(HWND, HINSTANCE, LPSTR, int)
 {
     COMRegister();
 }
 
+STDAPI_(void) CALLBACK DLLCOMUnregister(HWND, HINSTANCE, LPSTR, int);
 STDAPI_(void) CALLBACK DLLCOMUnregister(HWND, HINSTANCE, LPSTR, int)
 {
     COMUnregister();
diff --git a/qga/vss-win32/provider.cpp b/qga/vss-win32/provider.cpp
index cc72e5ef1b..a102a23fbf 100644
--- a/qga/vss-win32/provider.cpp
+++ b/qga/vss-win32/provider.cpp
@@ -45,7 +45,7 @@ const IID IID_IVssEnumObject = { 0xAE1C7110, 0x2F60, 0x11d3,
     {0x8A, 0x39, 0x00, 0xC0, 0x4F, 0x72, 0xD8, 0xE3} };
 
 
-void LockModule(BOOL lock)
+static void LockModule(BOOL lock)
 {
     if (lock) {
         InterlockedIncrement(&g_nComObjsInUse);
@@ -527,6 +527,9 @@ STDAPI DllCanUnloadNow()
     return g_nComObjsInUse == 0 ? S_OK : S_FALSE;
 }
 
+EXTERN_C
+BOOL WINAPI DllMain(HINSTANCE hinstDll, DWORD dwReason, LPVOID lpReserved);
+
 EXTERN_C
 BOOL WINAPI DllMain(HINSTANCE hinstDll, DWORD dwReason, LPVOID lpReserved)
 {
diff --git a/qga/vss-win32/requester.cpp b/qga/vss-win32/requester.cpp
index 9884c65e70..4401d55e3a 100644
--- a/qga/vss-win32/requester.cpp
+++ b/qga/vss-win32/requester.cpp
@@ -254,8 +254,8 @@ out:
     qga_debug_end;
 }
 
-DWORD get_reg_dword_value(HKEY baseKey, LPCSTR subKey, LPCSTR valueName,
-                          DWORD defaultData)
+static DWORD get_reg_dword_value(HKEY baseKey, LPCSTR subKey, LPCSTR valueName,
+                                 DWORD defaultData)
 {
     qga_debug_begin;
 
@@ -272,12 +272,12 @@ DWORD get_reg_dword_value(HKEY baseKey, LPCSTR subKey, LPCSTR valueName,
     return dwordData;
 }
 
-bool is_valid_vss_backup_type(VSS_BACKUP_TYPE vssBT)
+static bool is_valid_vss_backup_type(VSS_BACKUP_TYPE vssBT)
 {
     return (vssBT > VSS_BT_UNDEFINED && vssBT < VSS_BT_OTHER);
 }
 
-VSS_BACKUP_TYPE get_vss_backup_type(
+static VSS_BACKUP_TYPE get_vss_backup_type(
     VSS_BACKUP_TYPE defaultVssBT = DEFAULT_VSS_BACKUP_TYPE)
 {
     qga_debug_begin;