3 files changed, 12 insertions, 4 deletions
diff --git a/driver/utils/cwrapper.c b/driver/utils/cwrapper.c
index 5a30274ba7..522c2b329a 100644
--- a/driver/utils/cwrapper.c
+++ b/driver/utils/cwrapper.c
@@ -70,9 +70,12 @@ char *flattenAndQuoteArgs(char *ptr, int argc, char *argv[])
     return ptr;
 }
 
+/* This function takes a callback to be called after the creation of the child
+   process but before we block waiting for the child. Can be NULL.  */
 __attribute__((noreturn)) int run (char *exePath,
                                    int numArgs1, char **args1,
-                                   int numArgs2, char **args2)
+                                   int numArgs2, char **args2,
+                                   runCallback callback)
 {
     int i, cmdline_len;
     char *new_cmdline, *ptr;
@@ -134,6 +137,10 @@ __attribute__((noreturn)) int run (char *exePath,
     /* Synchronize input and wait for target to be ready.  */
     WaitForInputIdle(pi.hProcess, INFINITE);
 
+    /* If we have a registered callback then call it before we block.  */
+    if (callback)
+      callback();
+
     switch (WaitForSingleObject(pi.hProcess, INFINITE) ) {
     case WAIT_OBJECT_0:
     {
diff --git a/driver/utils/cwrapper.h b/driver/utils/cwrapper.h
index 324470e5ed..3e9ccd4fe5 100644
--- a/driver/utils/cwrapper.h
+++ b/driver/utils/cwrapper.h
@@ -1,5 +1,7 @@
 
 void die(const char *fmt, ...);
 char *mkString(const char *fmt, ...);
-__attribute__((noreturn)) int run(char *exePath, int numArgs1, char **args1, int numArgs2, char **args2);
-
+typedef void (*runCallback)(void);
+__attribute__((noreturn)) int run(char *exePath, int numArgs1, char **args1,
+                                  int numArgs2, char **args2,
+                                  runCallback callback);
diff --git a/driver/utils/dynwrapper.c b/driver/utils/dynwrapper.c
index a9250f58ba..7fb06e5945 100644
--- a/driver/utils/dynwrapper.c
+++ b/driver/utils/dynwrapper.c
@@ -155,7 +155,6 @@ HINSTANCE GetNonNullModuleHandle(LPTSTR dll) {
 typedef int (*hs_main_t)(int , char **, StgClosure *, RtsConfig);
 
 int main(int argc, char *argv[]) {
-    void *p;
     HINSTANCE hRtsDll, hProgDll;
     LPTSTR oldPath;