loadNativeObj: fail if we attempt to load an object that is already loaded

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(cherry picked from commit 74d8cadeef8a509f1ee612795f5af6142edb006c)

2 files changed, 32 insertions, 1 deletions

diff --git a/rts/Linker.c b/rts/Linker.c
index 33af36c356..62959b6707 100644
--- a/rts/Linker.c
+++ b/rts/Linker.c
@@ -1926,6 +1926,26 @@ static void * loadNativeObj_ELF (pathchar *path, char **errmsg)
 
    IF_DEBUG(linker, debugBelch("loadNativeObj_ELF %" PATH_FMT "\n", path));
 
+   // Loading the same object multiple times will lead to chaos
+   // because we will have two NativeCodes but one underlying handle,
+   // so let's fail if this happens.
+   for (nc = native_objects; nc; nc = nc->next) {
+       if (!pathcmp(nc->fileName,path)) {
+           copyErrmsg(errmsg, "native object already loaded");
+           return NULL;
+       }
+   }
+
+   // We also cannot load the same object if we are in the process of
+   // unloading it. We cannot resurrect it because we've already
+   // released the StablePtrs.
+   for (nc = unloaded_native_objects; nc; nc = nc->next) {
+       if (!pathcmp(nc->fileName,path)) {
+           copyErrmsg(errmsg, "unload in progress");
+           return NULL;
+       }
+   }
+
    retval = NULL;
    ACQUIRE_LOCK(&dl_mutex);
 
diff --git a/testsuite/tests/rts/linker_unload_native.c b/testsuite/tests/rts/linker_unload_native.c
index 14e7e2c44a..65e8a42259 100644
--- a/testsuite/tests/rts/linker_unload_native.c
+++ b/testsuite/tests/rts/linker_unload_native.c
@@ -41,7 +41,6 @@ int main (int argc, char *argv[])
 
     for (i=0; i < ITERATIONS; i++) {
         char* errmsg;
-        // load 2 libraries at once
         void* handle = loadNativeObj(OBJPATH, &errmsg);
         if (!handle) {
             errorBelch("loadNativeObj(%s) failed: %s", OBJPATH, errmsg);
@@ -49,6 +48,18 @@ int main (int argc, char *argv[])
             exit(1);
         }
 
+        // loading the same library again should fail
+        void* handle1 = loadNativeObj(OBJPATH, &errmsg);
+        if (!handle1) {
+            // don't spam the output file:
+            // errorBelch("loadNativeObj(%s) failed: %s", OBJPATH, errmsg);
+            free(errmsg);
+        } else {
+            errorBelch("loadNativeObj(%s) should have failed", OBJPATH);
+            exit(1);
+        }
+
+        // load 2 libraries at once
         void* handle2 = loadNativeObj(OBJPATH2, &errmsg);
         if (!handle2) {
             errorBelch("loadNativeObj(%s) failed: %s", OBJPATH2, errmsg);