[Libguestfs] [PATCH nbdkit 2/2] common/include: Fix MIN and MAX macros so they can be nested

[Richard W.M. Jones]

Thanks: Eric Blake
---
 common/include/minmax.h      | 21 +++++++++++++--------
 common/include/test-minmax.c | 14 ++++++++++++++
 2 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/common/include/minmax.h b/common/include/minmax.h
index d3e667ea..8d1fbf19 100644
--- a/common/include/minmax.h
+++ b/common/include/minmax.h
@@ -44,16 +44,23 @@
  * is required.
  */
 
+#include "unique-name.h"
+
+#undef MIN
+#define MIN(x, y) \
+  MIN_1((x), (y), NBDKIT_UNIQUE_NAME(_x), NBDKIT_UNIQUE_NAME(_y))
+#undef MAX
+#define MAX(x, y) \
+  MAX_1((x), (y), NBDKIT_UNIQUE_NAME(_x), NBDKIT_UNIQUE_NAME(_y))
+
 #ifdef HAVE_AUTO_TYPE
 
-#undef MIN
-#define MIN(x, y) ({                           \
+#define MIN_1(x, y, _x, _y) ({                 \
       __auto_type _x = (x);                    \
       __auto_type _y = (y);                    \
       _x < _y ? _x : _y;                       \
     })
-#undef MAX
-#define MAX(x, y) ({                           \
+#define MAX_1(x, y, _x, _y) ({                 \
       __auto_type _x = (x);                    \
       __auto_type _y = (y);                    \
       _x > _y ? _x : _y;                       \
@@ -61,14 +68,12 @@
 
 #else
 
-#undef MIN
-#define MIN(x, y) ({                           \
+#define MIN_1(x, y, _x, _y) ({                 \
       typeof (x) _x = (x);                     \
       typeof (y) _y = (y);                     \
       _x < _y ? _x : _y;                       \
     })
-#undef MAX
-#define MAX(x, y) ({                           \
+#define MAX_1(x, y, _x, _y) ({                 \
       typeof (x) _x = (x);                     \
       typeof (y) _y = (y);                     \
       _x > _y ? _x : _y;                       \
diff --git a/common/include/test-minmax.c b/common/include/test-minmax.c
index 7584ab27..32bc8a11 100644
--- a/common/include/test-minmax.c
+++ b/common/include/test-minmax.c
@@ -154,5 +154,19 @@ main (void)
   SIGNED_TEST (f, -FLT_MAX, FLT_MAX);
   SIGNED_TEST (d, -DBL_MAX, DBL_MAX);
 
+  /* Test that MIN and MAX can be nested.  This is really a compile
+   * test, but we do check the answer.
+   */
+  assert (MIN (MIN (1, 2), 3) == 1);
+  assert (MAX (MIN (1, 2), 3) == 3);
+  assert (MIN (MAX (1, 2), 3) == 2);
+  assert (MAX (MAX (1, 4), 3) == 4);
+  assert (MIN (3, MIN (1, 2)) == 1);
+  assert (MAX (3, MIN (1, 2)) == 3);
+  assert (MIN (3, MAX (1, 2)) == 2);
+  assert (MAX (3, MAX (1, 4)) == 4);
+  assert (MIN (MIN (1, MIN (2, 3)), 4) == 1);
+  assert (MAX (MAX (1, MAX (2, 3)), 4) == 4);
+
   exit (EXIT_SUCCESS);
 }
-- 
2.35.1