Qi.Tests: rule1: Fixed -Wuninitialized warning

libs/spirit/test/qi/rule1.cpp:75:47: warning: variable 'start' is uninitialized when used within its own initialization [-Wuninitialized]

.travis.yml

@@ -115,11 +115,12 @@ before_install:
     # Ignore some warnings
     feature.feature known-warnings : suppress : optional incidental propagated ;
     toolset.flags gcc.compile OPTIONS <known-warnings>suppress :
-        -Wno-uninitialized -Wno-bool-operation -Wno-sign-compare : unchecked ;
+        -Wno-maybe-uninitialized  # this warning is known to give false positives
+        -Wno-bool-operation -Wno-sign-compare : unchecked ;
     toolset.flags clang-linux.compile OPTIONS <known-warnings>suppress :
         -Wno-unused-command-line-argument # Sometimes it barks on -I and -stdlib
         -Wno-nested-anon-types # Boost.Random
-        -Wno-uninitialized : unchecked ;
+      : unchecked ;
 
   - |
     # Determining the root branch

test/qi/rule1.cpp

@@ -72,7 +72,9 @@ main()
         rule<char const*> a ('a');
         rule<char const*> b ('b');
         rule<char const*> c ('c');
-        rule<char const*> start = (a | b) >> (start | b);
+        rule<char const*> start;
+
+        start = (a | b) >> (start | b);
 
         BOOST_TEST(test("aaaabababaaabbb", start));
         BOOST_TEST(test("aaaabababaaabba", start, false));