From 90fcdc90d3559d8df98f5b7586dfef0ca45abf61 Mon Sep 17 00:00:00 2001
From: Mickey Rose <mickey.rose@seznam.cz>
Date: Tue, 16 Feb 2016 16:27:32 +0100
Subject: [PATCH] benchmarks: fix output formatting

snprintf is a better tool for this task, anyway, but here's what was
wrong with the stream formatting:

s << name << ":" << std::setw(45 - (int)s.tellp())

cannot be used to align columns, tellp() may return any of:
    0
    name.length()
    name.length() + strlen(":")

because the compiler is allowed to reorder the evaluation of
sub-expressions as it likes -- it may evaluate s.tellp() before
evaluating (s << name) or in-between (s << name) and (s << ":")

try with gcc-4.8
---
 benchmark/bench_framework.hpp | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/benchmark/bench_framework.hpp b/benchmark/bench_framework.hpp
index 52088e4e1..366f82706 100644
--- a/benchmark/bench_framework.hpp
+++ b/benchmark/bench_framework.hpp
@@ -9,7 +9,7 @@
 
 // stl
 #include <chrono>
-#include <iomanip>
+#include <cstdio> // snprintf
 #include <iostream>
 #include <set>
 #include <sstream>
@@ -96,11 +96,7 @@ int run(T const& test_runner, std::string const& name)
         {
             std::chrono::high_resolution_clock::time_point start;
             std::chrono::high_resolution_clock::duration elapsed;
-            std::stringstream s;
-            s << name << ":"
-                << std::setw(45 - (int)s.tellp()) << std::right
-                << " t:" << test_runner.threads()
-                << " i:" << test_runner.iterations();
+
             if (test_runner.threads() > 0)
             {
                 using thread_group = std::vector<std::unique_ptr<std::thread> >;
@@ -120,9 +116,15 @@ int run(T const& test_runner, std::string const& name)
                 test_runner();
                 elapsed = std::chrono::high_resolution_clock::now() - start;
             }
-            s << std::setw(65 - (int)s.tellp()) << std::right
-                << std::chrono::duration_cast<std::chrono::milliseconds>(elapsed).count() << " milliseconds\n";
-            std::clog << s.str();
+
+            char msg[200];
+            std::snprintf(msg, sizeof(msg),
+                    "%-43s %3zu threads %9zu iters %6.0f milliseconds",
+                    name.c_str(),
+                    test_runner.threads(),
+                    test_runner.iterations(),
+                    std::chrono::duration<double, std::milli>(elapsed).count());
+            std::clog << msg << "\n";
         }
         return 0;
     }