util: generalize code that checks whether PIDs are alive or unwaited for

[elogind.git] / src / shared / macro.h

diff --git a/src/shared/macro.h b/src/shared/macro.h
index 79bee0396c3a52c4bed07f28f1878915bad8b282..dfbc20142f753172ee8708f5e5aa94eca27fa66b 100644 (file)
--- a/src/shared/macro.h
+++ b/src/shared/macro.h
@@ -117,6 +117,13 @@ static inline size_t ALIGN_TO(size_t l, size_t ali) {
                         _a < _b ? _a : _b;      \
                 })
 
+#define LESS_BY(A,B)                            \
+        __extension__ ({                        \
+                        typeof(A) _A = (A);     \
+                        typeof(B) _B = (B);     \
+                        _A > _B ? _A - _B : 0;  \
+                })
+
 #ifndef CLAMP
 #define CLAMP(x, low, high)                                             \
         __extension__ ({                                                \