diff --git a/src/grib_accessor_class_bufr_string_values.c b/src/grib_accessor_class_bufr_string_values.c
index 88522299f..93c827e16 100644
--- a/src/grib_accessor_class_bufr_string_values.c
+++ b/src/grib_accessor_class_bufr_string_values.c
@@ -175,8 +175,8 @@ static int unpack_string_array(grib_accessor* a, char** buffer, size_t* len)
     grib_accessor* data        = 0;
     grib_context* c            = a->context;
     grib_vsarray* stringValues = NULL;
-    long l = 0, n = 0, tl;
-    size_t i, j;
+    size_t l = 0, tl;
+    size_t i, j, n = 0;
     /*char buf[25]={0,};*/
     char** b = buffer;
 
diff --git a/src/grib_accessor_class_g1end_of_interval_monthly.c b/src/grib_accessor_class_g1end_of_interval_monthly.c
index ebd3b7260..30cc178d0 100644
--- a/src/grib_accessor_class_g1end_of_interval_monthly.c
+++ b/src/grib_accessor_class_g1end_of_interval_monthly.c
@@ -169,7 +169,7 @@ static int unpack_double(grib_accessor* a, double* val, size_t* len)
     if (!a->dirty)
         return GRIB_SUCCESS;
 
-    if (*len != self->number_of_elements)
+    if (*len != (size_t)self->number_of_elements)
         return GRIB_ARRAY_TOO_SMALL;
 
     if ((ret = grib_get_string(grib_handle_of_accessor(a), self->verifyingMonth, verifyingMonth, &slen)) != GRIB_SUCCESS)
diff --git a/src/grib_bufr_descriptors_array.c b/src/grib_bufr_descriptors_array.c
index bf51c5e3e..2e4898640 100644
--- a/src/grib_bufr_descriptors_array.c
+++ b/src/grib_bufr_descriptors_array.c
@@ -185,8 +185,8 @@ void grib_bufr_descriptors_array_delete(bufr_descriptors_array* v)
 
 void grib_bufr_descriptors_array_delete_array(bufr_descriptors_array* v)
 {
-    grib_context* c;
-    int i;
+    grib_context* c = NULL;
+    size_t i = 0;
     bufr_descriptor** vv = NULL;
 
     if (!v)
diff --git a/src/grib_darray.c b/src/grib_darray.c
index 71672421b..bc7c8dab1 100644
--- a/src/grib_darray.c
+++ b/src/grib_darray.c
@@ -108,8 +108,8 @@ void grib_darray_delete(grib_context* c, grib_darray* v)
 
 double* grib_darray_get_array(grib_context* c, grib_darray* v)
 {
-    double* ret;
-    int i;
+    double* ret = NULL;
+    size_t i = 0;
     if (!v)
         return NULL;
     ret = (double*)grib_context_malloc_clear(c, sizeof(double) * v->n);
@@ -120,8 +120,8 @@ double* grib_darray_get_array(grib_context* c, grib_darray* v)
 
 int grib_darray_is_constant(grib_darray* v, double epsilon)
 {
-    int i;
-    double val;
+    size_t i = 0;
+    double val = 0;
     if (v->n == 1)
         return 1;
 
diff --git a/src/grib_oarray.c b/src/grib_oarray.c
index 6697e81a4..5e51751c5 100644
--- a/src/grib_oarray.c
+++ b/src/grib_oarray.c
@@ -102,8 +102,8 @@ void grib_oarray_delete_content(grib_context* c, grib_oarray* v)
 
 void** grib_oarray_get_array(grib_context* c, grib_oarray* v)
 {
-    void** ret;
-    int i;
+    void** ret = NULL;
+    size_t i = 0;
     if (!v)
         return NULL;
     ret = (void**)grib_context_malloc_clear(c, sizeof(char*) * v->n);
@@ -114,7 +114,8 @@ void** grib_oarray_get_array(grib_context* c, grib_oarray* v)
 
 void* grib_oarray_get(grib_oarray* v, int i)
 {
-    if (v == NULL || i > v->n - 1)
+    DebugAssert(i >= 0);
+    if (v == NULL || (size_t)i > v->n - 1)
         return NULL;
     return v->v[i];
 }
diff --git a/src/grib_sarray.c b/src/grib_sarray.c
index 869abde67..7ce3dcd9d 100644
--- a/src/grib_sarray.c
+++ b/src/grib_sarray.c
@@ -78,7 +78,7 @@ void grib_sarray_delete(grib_context* c, grib_sarray* v)
 
 void grib_sarray_delete_content(grib_context* c, grib_sarray* v)
 {
-    int i;
+    size_t i = 0;
     if (!v || !v->v)
         return;
     if (!c)
@@ -93,8 +93,8 @@ void grib_sarray_delete_content(grib_context* c, grib_sarray* v)
 
 char** grib_sarray_get_array(grib_context* c, grib_sarray* v)
 {
-    char** ret;
-    int i;
+    char** ret = NULL;
+    size_t i = 0;
     if (!v)
         return NULL;
     ret = (char**)grib_context_malloc_clear(c, sizeof(char*) * v->n);
diff --git a/src/grib_vdarray.c b/src/grib_vdarray.c
index bce2d0ab0..4063eb19a 100644
--- a/src/grib_vdarray.c
+++ b/src/grib_vdarray.c
@@ -19,7 +19,7 @@
 /* For debugging purposes */
 void grib_vdarray_print(const char* title, const grib_vdarray* vdarray)
 {
-    size_t i;
+    size_t i = 0;
     char text[100] = {0,};
     Assert(vdarray);
     printf("%s: vdarray.n=%lu\n", title, (unsigned long)vdarray->n);
@@ -99,7 +99,7 @@ void grib_vdarray_delete(grib_context* c, grib_vdarray* v)
 
 void grib_vdarray_delete_content(grib_context* c, grib_vdarray* v)
 {
-    int i;
+    size_t i = 0;
     if (!v || !v->v)
         return;
     if (!c)
@@ -114,7 +114,7 @@ void grib_vdarray_delete_content(grib_context* c, grib_vdarray* v)
 grib_darray** grib_vdarray_get_array(grib_context* c, grib_vdarray* v)
 {
     grib_darray** ret;
-    int i;
+    size_t i = 0;
     if (!v)
         return NULL;
     ret = (grib_darray**)grib_context_malloc_clear(c, sizeof(grib_darray*) * v->n);
diff --git a/src/grib_viarray.c b/src/grib_viarray.c
index 5c4f6692b..336e375bf 100644
--- a/src/grib_viarray.c
+++ b/src/grib_viarray.c
@@ -99,7 +99,7 @@ void grib_viarray_delete(grib_context* c, grib_viarray* v)
 
 void grib_viarray_delete_content(grib_context* c, grib_viarray* v)
 {
-    int i;
+    size_t i=0;
     if (!v || !v->v)
         return;
 
@@ -113,7 +113,7 @@ void grib_viarray_delete_content(grib_context* c, grib_viarray* v)
 grib_iarray** grib_viarray_get_array(grib_context* c, grib_viarray* v)
 {
     grib_iarray** ret;
-    int i;
+    size_t i = 0;
     if (!v)
         return NULL;
     ret = (grib_iarray**)grib_context_malloc_clear(c, sizeof(grib_iarray*) * v->n);
diff --git a/src/grib_vsarray.c b/src/grib_vsarray.c
index 227aa41fc..26b88a9db 100644
--- a/src/grib_vsarray.c
+++ b/src/grib_vsarray.c
@@ -84,7 +84,7 @@ void grib_vsarray_delete(grib_context* c, grib_vsarray* v)
 
 void grib_vsarray_delete_content(grib_context* c, grib_vsarray* v)
 {
-    int i;
+    size_t i = 0;
     if (!v || !v->v)
         return;
     if (!c)
@@ -100,7 +100,7 @@ void grib_vsarray_delete_content(grib_context* c, grib_vsarray* v)
 grib_sarray** grib_vsarray_get_array(grib_context* c, grib_vsarray* v)
 {
     grib_sarray** ret;
-    int i;
+    size_t i = 0;
     if (!v)
         return NULL;
     ret = (grib_sarray**)grib_context_malloc_clear(c, sizeof(grib_sarray*) * v->n);
diff --git a/tools/grib_check_gaussian_grid.c b/tools/grib_check_gaussian_grid.c
index 1b1024b57..54fa684f2 100644
--- a/tools/grib_check_gaussian_grid.c
+++ b/tools/grib_check_gaussian_grid.c
@@ -185,7 +185,7 @@ static int process_file(const char* filename)
 
             GRIB_CHECK(grib_get_size(h, "pl", &pl_len), 0);
             assert(pl_len > 0);
-            if (pl_len != 2 * N) {
+            if (pl_len != (size_t)(2 * N)) {
                 error(filename, msg_num, "Length of pl array is %ld but should be 2*N (%ld)\n", pl_len, 2 * N);
             }
             pl = (long*)malloc(pl_len * sizeof(long));
@@ -232,7 +232,7 @@ static int process_file(const char* filename)
         }
 
         GRIB_CHECK(grib_get_size(h, "values", &sizeOfValuesArray), 0);
-        if (sizeOfValuesArray != numberOfDataPoints) {
+        if (sizeOfValuesArray != (size_t)numberOfDataPoints) {
             error(filename, msg_num, "Number of data points %d different from size of values array %d\n",
                   numberOfDataPoints, sizeOfValuesArray);
         }