fix: incorrect number of dirty pages printed (#766)

The `log_dirty_bitmap` function in `dma.c` would output the wrong number of dirty pages due to the `char` of the bitmap being sign-extended when implicitly being converted to `unsigned int` for `__builtin_popcount`. By adding an intermediate cast to `uint8_t` we avoid this incorrect behaviour. See #746 (comment). Signed-off-by: William Henderson <[email protected]>
nutanix · Aug 23, 2023 · 149aa84 · 149aa84
1 parent cfb7d90
commit 149aa84
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/lib/dma.c b/lib/dma.c
@@ -535,7 +535,7 @@ log_dirty_bitmap(vfu_ctx_t *vfu_ctx, dma_memory_region_t *region,
     size_t i;
     size_t count;
     for (i = 0, count = 0; i < size; i++) {
-        count += __builtin_popcount(bitmap[i]);
+        count += __builtin_popcount((uint8_t)bitmap[i]);
     }
     vfu_log(vfu_ctx, LOG_DEBUG, "dirty pages: get [%p, %p), %zu dirty pages",
             region->info.iova.iov_base, iov_end(&region->info.iova),