Andres Freund <andres@anarazel.de> writes:
> Wonder if we should try to get rid of the problem by also fixing the double
> evaluation of val? I think something like
Good idea. The attached also silences the warning, and getting rid
of the double-eval hazard seems like a net win.
> Might also be worth adding an assertion that base < val.
Did that too. On the whole I like this better.
regards, tom lane
diff --git a/src/include/utils/relptr.h b/src/include/utils/relptr.h
index fdc2124d2c..cc80a7200d 100644
--- a/src/include/utils/relptr.h
+++ b/src/include/utils/relptr.h
@@ -56,11 +56,24 @@
#define relptr_is_null(rp) \
((rp).relptr_off == 0)
+/* We use this inline to avoid double eval of "val" in relptr_store */
+static inline Size
+relptr_store_eval(char *base, char *val)
+{
+ if (val == NULL)
+ return 0;
+ else
+ {
+ Assert(val > base);
+ return val - base;
+ }
+}
+
#ifdef HAVE__BUILTIN_TYPES_COMPATIBLE_P
#define relptr_store(base, rp, val) \
(AssertVariableIsOfTypeMacro(base, char *), \
AssertVariableIsOfTypeMacro(val, __typeof__((rp).relptr_type)), \
- (rp).relptr_off = ((val) == NULL ? 0 : ((char *) (val)) - (base)))
+ (rp).relptr_off = relptr_store_eval(base, (char *) (val)))
#else
/*
* If we don't have __builtin_types_compatible_p, assume we might not have
@@ -68,7 +81,7 @@
*/
#define relptr_store(base, rp, val) \
(AssertVariableIsOfTypeMacro(base, char *), \
- (rp).relptr_off = ((val) == NULL ? 0 : ((char *) (val)) - (base)))
+ (rp).relptr_off = relptr_store_eval(base, (char *) (val)))
#endif
#define relptr_copy(rp1, rp2) \
