From cf8871ae40ae85f86b0d396b6af1eb657134ffc1 Mon Sep 17 00:00:00 2001
From: Willy Tarreau <w@1wt.eu>
Date: Wed, 6 Aug 2025 19:05:29 +0200
Subject: [PATCH] BUILD: compat: provide relaxed versions of the MIN/MAX macros

In 3.0 the MIN/MAX macros were converted to compound expressions with
commit 0999e3d959 ("CLEANUP: compat: make the MIN/MAX macros more
reliable"). However with older compilers these are not supported out
of code blocks (e.g. to initialize variables or struct members). This
is the case on Solaris 10 with gcc-5.5 when QUIC doesn't compile
anymore with the future pool registration:

  In file included from include/haproxy/quic_tx.h:26:0,
                   from src/quic_tx.c:15:
  include/haproxy/compat.h:106:19: error: braced-group within expression allowed only inside a function
   #define MAX(a, b) ({    \
                     ^
  include/haproxy/pool.h:41:11: note: in definition of macro '__REGISTER_POOL'
     .size = _size,           \
             ^
  ...
  include/haproxy/quic_tx-t.h:6:29: note: in expansion of macro 'MAX'
   #define QUIC_MAX_CC_BUFSIZE MAX(QUIC_INITIAL_IPV6_MTU, QUIC_INITIAL_IPV4_MTU)

Let's provide the old relaxed versions as _MIN/_MAX for use with constants
like such cases where it's certain that there is no risk. A previous attempt
using __builtin_constant_p() to switch between the variants did not work,
and it's really not worth the hassle of going this far.
---
 include/haproxy/compat.h | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/include/haproxy/compat.h b/include/haproxy/compat.h
index e4fec3e1b..ad91b901c 100644
--- a/include/haproxy/compat.h
+++ b/include/haproxy/compat.h
@@ -94,11 +94,21 @@ typedef struct { } empty_t;
 # endif
 #endif
 
+/* unsafe ones for use with constant macros needed in initializers */
+#ifndef _MIN
+#define _MIN(a, b) ((a < b) ? a : b)
+#endif
+
+#ifndef _MAX
+#define _MAX(a, b) ((a > b) ? a : b)
+#endif
+
+/* safe versions for use anywhere except in initializers */
 #ifndef MIN
 #define MIN(a, b) ({				\
 	typeof(a) _a = (a);			\
 	typeof(a) _b = (b);			\
-	((_a < _b) ? _a : _b);			\
+	_MIN(_a, _b);				\
 })
 #endif
 
@@ -106,7 +116,7 @@ typedef struct { } empty_t;
 #define MAX(a, b) ({				\
 	typeof(a) _a = (a);			\
 	typeof(a) _b = (b);			\
-	((_a > _b) ? _a : _b);			\
+	_MAX(_a, _b);				\
 })
 #endif