Clarification about the custom interface and macros.

* doc/mpfr.texi: added some text in Section "Custom Interface".
* src/mpfr.h: replaced the remaining FIXME by another comment.

git-svn-id: https://scm.gforge.inria.fr/anonscm/svn/mpfr/trunk@14462 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 6 insertions, 0 deletions

diff --git a/doc/mpfr.texi b/doc/mpfr.texi
index 424997714..2622b1c4b 100644
--- a/doc/mpfr.texi
+++ b/doc/mpfr.texi
@@ -3902,6 +3902,12 @@ to the application.
 Each function in this interface is also implemented as a macro for
 efficiency reasons: for example @code{mpfr_custom_init (s, p)}
 uses the macro, while @code{(mpfr_custom_init) (s, p)} uses the function.
+Note that the macro may evaluate arguments multiple times (or none).
+Moreover, macros implementing functions with the @code{void} return type
+may not be used in contexts where an expression is expected, e.g., inside
+@code{for(...)} or before a comma operator.
+@c These limitations with macros cannot be avoided in a C90 compatible way.
+@c In the future, inline functions could be used.
 
 Note 1: MPFR functions may still initialize temporary floating-point numbers
 using @code{mpfr_init} and similar functions. See Custom Allocation (GNU MP)@.