[PATCH nft 1/2] utils: add memory_allocation_check() helper

[Thomas Haller <thaller@redhat.com>]

libnftables kills the process on out of memory (xmalloc()), so
when we use libraries that propagate ENOMEM to libnftables, we
also abort the process.

For example:

     nlr = nftnl_rule_alloc();
     if (!nlr)
          memory_allocation_error();

Add memory_allocation_check() macro which can simplify this common
check to:

     nlr = memory_allocation_check(nftnl_rule_alloc());

Signed-off-by: Thomas Haller <thaller@redhat.com>
---
 include/utils.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/include/utils.h b/include/utils.h
index 36a28f893667..fcd7c598fe9f 100644
--- a/include/utils.h
+++ b/include/utils.h
@@ -142,6 +142,16 @@ extern void __memory_allocation_error(const char *filename, uint32_t line) __nor
 #define memory_allocation_error()		\
 	__memory_allocation_error(__FILE__, __LINE__);
 
+#define memory_allocation_check(cmd)               \
+	({                                         \
+		typeof((cmd)) _v = (cmd);          \
+		const void *const _v2 = _v;        \
+                                                   \
+		if (!_v2)                          \
+			memory_allocation_error(); \
+		_v;                                \
+	})
+
 extern void xfree(const void *ptr);
 extern void *xmalloc(size_t size);
 extern void *xmalloc_array(size_t nmemb, size_t size);
-- 
2.41.0