Always use our own MAX/MIN definitions

code in src/shared/macro.h only defined MAX/MIN in case
they were not defined previously. however the MAX/MIN
macros implemented in glibc are not of the "safe" kind but defined
as:

define MIN(a,b) (((a)<(b))?(a):(b))
define MAX(a,b) (((a)>(b))?(a):(b))

Avoid nasty side effects by using our own versions instead.

Also fix the warnings derived from this change.

[zj: - modify MAX3 macro to fix warning about _a shadowing _a,
     - do bootchart/svg.c too,
     - remove unused MIN3.]

src/shared/macro.h

@@ -71,29 +71,27 @@ static inline size_t ALIGN_TO(size_t l, size_t ali) {
         const typeof( ((type *)0)->member ) *__mptr = (ptr); \
         (type *)( (char *)__mptr - offsetof(type,member) );})
 
-#ifndef MAX
-#define MAX(a,b)                                \
-        __extension__ ({                        \
-                        typeof(a) _a = (a);     \
-                        typeof(b) _b = (b);     \
-                        _a > _b ? _a : _b;      \
+#undef MAX
+#define MAX(a,b)                                 \
+        __extension__ ({                         \
+                        typeof(a) _a = (a);      \
+                        typeof(b) _b = (b);      \
+                        _a > _b ? _a : _b;       \
                 })
-#endif
 
-#define MAX3(a,b,c)                             \
-        MAX(MAX(a,b),c)
+#define MAX3(x,y,z)                              \
+        __extension__ ({                         \
+                        typeof(x) _c = MAX(x,y); \
+                        MAX(_c, z);              \
+                })
 
-#ifndef MIN
+#undef MIN
 #define MIN(a,b)                                \
         __extension__ ({                        \
                         typeof(a) _a = (a);     \
                         typeof(b) _b = (b);     \
                         _a < _b ? _a : _b;      \
                 })
-#endif
-
-#define MIN3(a,b,c)                             \
-        MIN(MIN(a,b),c)
 
 #ifndef CLAMP
 #define CLAMP(x, low, high)                                             \

src/shared/prioq.c

@@ -159,7 +159,7 @@ int prioq_put(Prioq *q, void *data, unsigned *idx) {
                 unsigned n;
                 struct prioq_item *j;
 
-                n = MAX((q->n_items+1) * 2, 16);
+                n = MAX((q->n_items+1) * 2, 16u);
                 j = realloc(q->items, sizeof(struct prioq_item) * n);
                 if (!j)
                         return -ENOMEM;

src/shared/util.c

@@ -5862,7 +5862,7 @@ void* greedy_realloc(void **p, size_t *allocated, size_t need) {
         if (*allocated >= need)
                 return *p;
 
-        a = MAX(64, need * 2);
+        a = MAX(64u, need * 2);
         q = realloc(*p, a);
         if (!q)
                 return NULL;