Clarify condition on BUF_SIZE in monitor example.

Thanks to Terje Mathiesen for pointing out this issue.

diff --git a/doc/reference.texi b/doc/reference.texi
index 5e4db9e8fc482065383f73f5fe4bb7f7049b4571..3d7d9bcbd2bbb2df58152293f4b09173cb60aff4 100644 (file)
--- a/doc/reference.texi
+++ b/doc/reference.texi
@@ -844,6 +844,11 @@ char get (void) @{
 @}
 @end example
 
 @}
 @end example
 

+Note that @code{BUF_SIZE} must divide evenly into @code{SIZE_MAX + 1}
+for the above code to be completely correct.  Otherwise, it will fail
+the first time @code{head} wraps around to 0.  In practice,
+@code{BUF_SIZE} would ordinarily be a power of 2.
+

 @node Optimization Barriers
 @subsection Optimization Barriers
 
 @node Optimization Barriers
 @subsection Optimization Barriers