Fix: make umf_ba_linear_alloc(0) always return NULL

umf_ba_linear_alloc(0) didn't return NULL and
umf_ba_linear_free(umf_ba_linear_alloc(0)) always failed,
because pool_contains_ptr(umf_ba_linear_alloc(0)) always
returned false, since umf_ba_linear_alloc(0) pointed
at the very end of the pool (ptr == (char *)pool + pool_size).

Fixes: #260

Signed-off-by: Lukasz Dorau <lukasz.dorau@intel.com>

Author: ldorau

src/base_alloc/base_alloc_linear.c

@@ -118,6 +118,9 @@ umf_ba_linear_pool_t *umf_ba_linear_create(size_t pool_size) {
 }
 
 void *umf_ba_linear_alloc(umf_ba_linear_pool_t *pool, size_t size) {
+    if (size == 0) {
+        return NULL;
+    }
     size_t aligned_size = ALIGN_UP(size, MEMORY_ALIGNMENT);
     util_mutex_lock(&pool->metadata.lock);
     if (pool->metadata.size_left < aligned_size) {

test/test_base_alloc_linear.cpp

@@ -73,10 +73,11 @@ TEST_F(test, baseAllocLinearMultiThreadedAllocMemset) {
         } buffer[ITERATIONS];
 
         for (int i = 0; i < ITERATIONS; i++) {
-            buffer[i].size =
-                (size_t)((rand() / (double)RAND_MAX) * MAX_ALLOCATION_SIZE);
-            buffer[i].ptr =
-                (unsigned char *)umf_ba_linear_alloc(pool, buffer[i].size);
+            // size must be greater than 0
+            size_t size = (size_t)(1 + (MAX_ALLOCATION_SIZE - 1) *
+                                           (rand() / (double)RAND_MAX));
+            buffer[i].size = size;
+            buffer[i].ptr = (unsigned char *)umf_ba_linear_alloc(pool, size);
             UT_ASSERTne(buffer[i].ptr, NULL);
             memset(buffer[i].ptr, (i + TID) & 0xFF, buffer[i].size);
         }