From: Lennart Poettering <lennart@poettering.net>
Date: Fri, 29 May 2020 21:27:59 +0000 (+0200)
Subject: macro: add CONST_MIN() similar to CONST_MAX()
X-Git-Tag: v246-rc1~84^2~17
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=d1d8f0f369ce386878e79d56b2795397902bc221;p=thirdparty%2Fsystemd.git

macro: add CONST_MIN() similar to CONST_MAX()
---

diff --git a/src/basic/macro.h b/src/basic/macro.h
index 78e4262e41d..fd8772f377f 100644
--- a/src/basic/macro.h
+++ b/src/basic/macro.h
@@ -286,6 +286,15 @@ static inline size_t GREEDY_ALLOC_ROUND_UP(size_t l) {
                 UNIQ_T(A, aq) < UNIQ_T(B, bq) ? UNIQ_T(A, aq) : UNIQ_T(B, bq); \
         })
 
+/* evaluates to (void) if _A or _B are not constant or of different types */
+#define CONST_MIN(_A, _B) \
+        (__builtin_choose_expr(                                         \
+                __builtin_constant_p(_A) &&                             \
+                __builtin_constant_p(_B) &&                             \
+                __builtin_types_compatible_p(typeof(_A), typeof(_B)),   \
+                ((_A) < (_B)) ? (_A) : (_B),                            \
+                VOID_0))
+
 #define MIN3(x, y, z)                                   \
         ({                                              \
                 const typeof(x) _c = MIN(x, y);         \