From dbd70d4884916009fa89e7423c71ca2c226c51f1 Mon Sep 17 00:00:00 2001
From: Patrick Niklaus <patrick.niklaus@student.kit.edu>
Date: Fri, 13 Jan 2017 15:56:36 +0000
Subject: [PATCH] Throw exception with more helpful error message when shmctl
 fails

---
 include/storage/shared_memory.hpp | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/include/storage/shared_memory.hpp b/include/storage/shared_memory.hpp
index 0190b0207..d199f40b5 100644
--- a/include/storage/shared_memory.hpp
+++ b/include/storage/shared_memory.hpp
@@ -111,10 +111,35 @@ class SharedMemory
     {
         auto shmid = shm.get_shmid();
         ::shmid_ds xsi_ds;
+        const auto errorToMessage = [](int error) -> std::string {
+            switch (error)
+            {
+            case EPERM:
+                return "EPERM";
+                break;
+            case EACCES:
+                return "ACCESS";
+                break;
+            case EINVAL:
+                return "EINVAL";
+                break;
+            case EFAULT:
+                return "EFAULT";
+                break;
+            default:
+                return "Unknown Error " + std::to_string(error);
+                break;
+            }
+        };
+
         do
         {
             int ret = ::shmctl(shmid, IPC_STAT, &xsi_ds);
-            (void)ret; // no unused warning
+            if (ret < 0)
+            {
+                throw util::exception("shmctl encountered an error: " + errorToMessage(ret) +
+                                      SOURCE_REF);
+            }
             BOOST_ASSERT(ret >= 0);
 
             std::this_thread::sleep_for(std::chrono::microseconds(100));