From 2b761d5f50b7dc17dc55c31980c2253c37b3c920 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Thu, 11 May 2017 17:06:07 +0200
Subject: [PATCH] Make fmt() non-recursive

---
 src/libutil/logging.hh |  2 +-
 src/libutil/types.hh   | 17 ++++++-----------
 2 files changed, 7 insertions(+), 12 deletions(-)

diff --git a/src/libutil/logging.hh b/src/libutil/logging.hh
index 81aebccdc..a8c69dbd9 100644
--- a/src/libutil/logging.hh
+++ b/src/libutil/logging.hh
@@ -88,7 +88,7 @@ template<typename... Args>
 inline void warn(const std::string & fs, Args... args)
 {
     boost::format f(fs);
-    formatHelper(f, args...);
+    nop{boost::io::detail::feed(f, args)...};
     logger->warn(f.str());
 }
 
diff --git a/src/libutil/types.hh b/src/libutil/types.hh
index 1429c2385..9f32d31ad 100644
--- a/src/libutil/types.hh
+++ b/src/libutil/types.hh
@@ -32,6 +32,11 @@ using std::vector;
 using boost::format;
 
 
+/* A variadic template that does nothing. Useful to call a function
+   for all variadic arguments but ignoring the result. */
+struct nop { template<typename... T> nop(T...) {} };
+
+
 struct FormatOrString
 {
     string s;
@@ -46,16 +51,6 @@ struct FormatOrString
    ... a_n’. However, ‘fmt(s)’ is equivalent to ‘s’ (so no %-expansion
    takes place). */
 
-inline void formatHelper(boost::format & f)
-{
-}
-
-template<typename T, typename... Args>
-inline void formatHelper(boost::format & f, T x, Args... args)
-{
-    formatHelper(f % x, args...);
-}
-
 inline std::string fmt(const std::string & s)
 {
     return s;
@@ -75,7 +70,7 @@ template<typename... Args>
 inline std::string fmt(const std::string & fs, Args... args)
 {
     boost::format f(fs);
-    formatHelper(f, args...);
+    nop{boost::io::detail::feed(f, args)...};
     return f.str();
 }