Fix compilation error on some versions of GCC

src/libexpr/primops.cc:42:8: error: looser throw specifier for 'virtual nix::InvalidPathError::~InvalidPathError()'
src/libexpr/nixexpr.hh:12:1: error:   overriding 'virtual nix::EvalError::~EvalError() noexcept (true)'

http://hydra.nixos.org/build/12385750

2 files changed, 3 insertions, 2 deletions

diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 01c7ca444119..543266b22aa1 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -44,6 +44,7 @@ struct InvalidPathError : EvalError
     Path path;
     InvalidPathError(const Path & path) :
         EvalError(format("path `%1%' is not valid") % path), path(path) {};
+    ~InvalidPathError() throw () { };
 };
 
 
diff --git a/src/libutil/types.hh b/src/libutil/types.hh
index 4b5ce9a78c48..906a959e3079 100644
--- a/src/libutil/types.hh
+++ b/src/libutil/types.hh
@@ -41,8 +41,8 @@ public:
     BaseError(const FormatOrString & fs, unsigned int status = 1);
     ~BaseError() throw () { };
     const char * what() const throw () { return err.c_str(); }
-    const string & msg() const throw () { return err; }
-    const string & prefix() const throw () { return prefix_; }
+    const string & msg() const { return err; }
+    const string & prefix() const { return prefix_; }
     BaseError & addPrefix(const FormatOrString & fs);
 };