Use std::less to detect string overlap in path::append.

Pointer ordering is unspecified if the pointers are to unrelated
objects, which triggers ASAN warnings. Use std::less to avoid this.

Closes #335.

Author: Lastique

build/Jamfile.v2

@@ -137,6 +137,7 @@ local cxx_requirements = [ requires
     cxx11_defaulted_moves
     cxx11_deleted_functions
     cxx11_function_template_default_args
+    cxx11_unified_initialization_syntax
     cxx11_final
     cxx11_override
 ] ;

doc/release_history.html

@@ -40,6 +40,11 @@
   </tr>
 </table>
 
+<h2>1.89.0</h2>
+<ul>
+  <li>Corrected ASAN warnings about comparing pointers to potentially unrelated objects in <code>path::append</code>. (<a href="https://github.com/boostorg/filesystem/issues/335">#335</a>)</li>
+</ul>
+
 <h2>1.87.0</h2>
 <ul>
   <li>As was announced in 1.84.0, Windows versions prior to 10 are no longer supported.</li>

src/path.cpp

@@ -15,6 +15,7 @@
 #include <boost/filesystem/detail/path_traits.hpp> // codecvt_error_category()
 #include <boost/system/error_category.hpp> // for BOOST_SYSTEM_HAS_CONSTEXPR
 #include <boost/assert.hpp>
+#include <functional>
 #include <algorithm>
 #include <iterator>
 #include <utility>
@@ -139,6 +140,13 @@ inline void first_element(string_type const& src, size_type& element_pos, size_t
     first_element(src, element_pos, element_size, src.size());
 }
 
+// Checks if the second string overlaps in memory with the first string
+inline bool is_overlapping(string_type const& str, const value_type* arg)
+{
+    std::less< const value_type* > ptr_less{};
+    return !(ptr_less(arg, str.data()) || ptr_less(str.data() + str.size(), arg));
+}
+
 } // unnamed namespace
 
 //--------------------------------------------------------------------------------------//
@@ -478,7 +486,7 @@ BOOST_FILESYSTEM_DECL void path_algorithms::append_v3(path& p, const value_type*
 {
     if (begin != end)
     {
-        if (BOOST_LIKELY(begin < p.m_pathname.data() || begin >= (p.m_pathname.data() + p.m_pathname.size())))
+        if (BOOST_LIKELY(!is_overlapping(p.m_pathname, begin)))
         {
             if (!detail::is_directory_separator(*begin))
                 path_algorithms::append_separator_if_needed(p);
@@ -497,7 +505,7 @@ BOOST_FILESYSTEM_DECL void path_algorithms::append_v4(path& p, const value_type*
 {
     if (begin != end)
     {
-        if (BOOST_LIKELY(begin < p.m_pathname.data() || begin >= (p.m_pathname.data() + p.m_pathname.size())))
+        if (BOOST_LIKELY(!is_overlapping(p.m_pathname, begin)))
         {
             const size_type that_size = end - begin;
             size_type that_root_name_size = 0;