diff --git a/examples/arkode/CXX_parallel/ark_brusselator1D.h b/examples/arkode/CXX_parallel/ark_brusselator1D.h
index 38cc6ee7a4..b95390bc4a 100644
--- a/examples/arkode/CXX_parallel/ark_brusselator1D.h
+++ b/examples/arkode/CXX_parallel/ark_brusselator1D.h
@@ -12,6 +12,9 @@
  * SUNDIALS Copyright End
  * ---------------------------------------------------------------------------*/
 
+#ifndef _ARK_BRUSSELATOR1D_H
+#define _ARK_BRUSSELATOR1D_H
+
 #include <cmath>
 #include <cstdio>
 #include <cstdlib>
@@ -266,3 +269,5 @@ static int check_retval(void* returnvalue, const char* funcname, int opt);
 static void gpuAssert(GPU_PREFIX(Error_t) code, const char* file, int line,
                       int abort);
 #endif
+
+#endif
diff --git a/examples/nvector/test_nvector.h b/examples/nvector/test_nvector.h
index 9ff1c6163e..7984712649 100644
--- a/examples/nvector/test_nvector.h
+++ b/examples/nvector/test_nvector.h
@@ -15,6 +15,9 @@
  * test an NVECTOR module implementation.
  * -----------------------------------------------------------------*/
 
+#ifndef _TEST_NVECTOR_H
+#define _TEST_NVECTOR_H
+
 #include <math.h>
 #include <sundials/sundials_types.h>
 
@@ -146,3 +149,5 @@ void SetTiming(int onoff, int myid);
 #ifdef __cplusplus
 }
 #endif
+
+#endif
diff --git a/examples/utilities/custom_memory_helper_gpu.h b/examples/utilities/custom_memory_helper_gpu.h
index ca5950a7f9..08872f983e 100644
--- a/examples/utilities/custom_memory_helper_gpu.h
+++ b/examples/utilities/custom_memory_helper_gpu.h
@@ -15,6 +15,9 @@
  * unmanaged memory only and synchronous copies.
  * -----------------------------------------------------------------*/
 
+#ifndef _CUSTOM_MEMORY_HELPER_GPU_H
+#define _CUSTOM_MEMORY_HELPER_GPU_H
+
 #include <assert.h>
 #include <string.h>
 #if defined(__NVCC__)
@@ -157,3 +160,5 @@ SUNMemoryHelper MyMemoryHelper(SUNContext sunctx)
 
   return helper;
 }
+
+#endif
diff --git a/examples/utilities/custom_memory_helper_sycl.h b/examples/utilities/custom_memory_helper_sycl.h
index 6af7c0d435..3135f3ad5d 100644
--- a/examples/utilities/custom_memory_helper_sycl.h
+++ b/examples/utilities/custom_memory_helper_sycl.h
@@ -15,6 +15,9 @@
  * unmanaged memory only and synchronous copies.
  * -----------------------------------------------------------------*/
 
+#ifndef _CUSTOM_MEMORY_HELPER_SYCL_H
+#define _CUSTOM_MEMORY_HELPER_SYCL_H
+
 #include <cstdlib>
 #include <sundials/sundials_memory.h>
 #include <sycl/sycl.hpp>
@@ -116,3 +119,5 @@ SUNMemoryHelper MyMemoryHelper(SUNContext sunctx)
 
   return helper;
 }
+
+#endif
diff --git a/src/arkode/arkode.c b/src/arkode/arkode.c
index 69ec2d37fe..eac2af4222 100644
--- a/src/arkode/arkode.c
+++ b/src/arkode/arkode.c
@@ -133,6 +133,7 @@ ARKodeMem arkCreate(SUNContext sunctx)
   {
     arkProcessError(NULL, ARK_MEM_FAIL, __LINE__, __func__, __FILE__,
                     "Allocation of step adaptivity structure failed");
+    arkFree((void**)&ark_mem);
     return (NULL);
   }
   ark_mem->lrw += ARK_ADAPT_LRW;
@@ -144,6 +145,7 @@ ARKodeMem arkCreate(SUNContext sunctx)
   {
     arkProcessError(NULL, ARK_MEM_FAIL, __LINE__, __func__, __FILE__,
                     "Allocation of step controller object failed");
+    arkFree((void**)&ark_mem);
     return (NULL);
   }
   ark_mem->hadapt_mem->owncontroller = SUNTRUE;
@@ -180,6 +182,7 @@ ARKodeMem arkCreate(SUNContext sunctx)
   {
     arkProcessError(NULL, 0, __LINE__, __func__, __FILE__,
                     "Error setting default solver options");
+    arkFree((void**)&ark_mem);
     return (NULL);
   }
 
diff --git a/src/arkode/arkode_arkstep.c b/src/arkode/arkode_arkstep.c
index 7e4361c516..0d7fc94394 100644
--- a/src/arkode/arkode_arkstep.c
+++ b/src/arkode/arkode_arkstep.c
@@ -89,6 +89,7 @@ void* ARKStepCreate(ARKRhsFn fe, ARKRhsFn fi, sunrealtype t0, N_Vector y0,
   {
     arkProcessError(ark_mem, ARK_MEM_FAIL, __LINE__, __func__, __FILE__,
                     MSG_ARK_ARKMEM_FAIL);
+    ARKStepFree((void**)&ark_mem);
     return (NULL);
   }
   memset(step_mem, 0, sizeof(struct ARKodeARKStepMemRec));
diff --git a/src/arkode/arkode_erkstep.c b/src/arkode/arkode_erkstep.c
index 1e80ea0f20..8fec869acf 100644
--- a/src/arkode/arkode_erkstep.c
+++ b/src/arkode/arkode_erkstep.c
@@ -85,6 +85,7 @@ void* ERKStepCreate(ARKRhsFn f, sunrealtype t0, N_Vector y0, SUNContext sunctx)
   {
     arkProcessError(ark_mem, ARK_MEM_FAIL, __LINE__, __func__, __FILE__,
                     MSG_ARK_ARKMEM_FAIL);
+    ERKStepFree((void**)&ark_mem);
     return (NULL);
   }
   memset(step_mem, 0, sizeof(struct ARKodeERKStepMemRec));
@@ -101,6 +102,7 @@ void* ERKStepCreate(ARKRhsFn f, sunrealtype t0, N_Vector y0, SUNContext sunctx)
   {
     arkProcessError(ark_mem, retval, __LINE__, __func__, __FILE__,
                     "Error setting default solver options");
+    ERKStepFree((void**)&ark_mem);
     return (NULL);
   }
 
@@ -124,6 +126,7 @@ void* ERKStepCreate(ARKRhsFn f, sunrealtype t0, N_Vector y0, SUNContext sunctx)
   {
     arkProcessError(ark_mem, retval, __LINE__, __func__, __FILE__,
                     "Unable to initialize main ARKODE infrastructure");
+    ERKStepFree((void**)&ark_mem);
     return (NULL);
   }
 
diff --git a/src/sundials/sundials_adiak_metadata.h b/src/sundials/sundials_adiak_metadata.h
index 8013dbdc6b..4e7e908a66 100644
--- a/src/sundials/sundials_adiak_metadata.h
+++ b/src/sundials/sundials_adiak_metadata.h
@@ -12,6 +12,9 @@
  * SUNDIALS Copyright End
  * ----------------------------------------------------------------*/
 
+#ifndef _SUNDIALS_ADIAK_METADATA_H
+#define _SUNDIALS_ADIAK_METADATA_H
+
 #ifdef SUNDIALS_ADIAK_ENABLED
 #include <adiak.h>
 
@@ -142,3 +145,5 @@ static void sunAdiakCollectMetadata()
 #endif
 }
 #endif
+
+#endif
diff --git a/src/sundials/sundials_iterative_impl.h b/src/sundials/sundials_iterative_impl.h
index 5ebf796761..ea6c17c10e 100644
--- a/src/sundials/sundials_iterative_impl.h
+++ b/src/sundials/sundials_iterative_impl.h
@@ -15,6 +15,9 @@
  * different iterative solvers.
  * ---------------------------------------------------------------------------*/
 
+#ifndef _SUNDIALS_ITERATIVE_IMPL_H
+#define _SUNDIALS_ITERATIVE_IMPL_H
+
 #include <sundials/sundials_iterative.h>
 
 /* -----------------------------------------------------------------------------
@@ -33,3 +36,5 @@ struct _SUNQRData
   N_Vector vtemp2;
   sunrealtype* temp_array;
 };
+
+#endif