Add data() member to float128

include/boost/multiprecision/float128.hpp

@@ -296,6 +296,14 @@ struct float128_backend
    {
       return m_value;
    }
+   BOOST_MP_CXX14_CONSTEXPR float128_type& data()
+   {
+       return m_value;
+   }
+   BOOST_MP_CXX14_CONSTEXPR const float128_type& data() const
+   {
+       return m_value;
+   }
 };
 
 inline BOOST_MP_CXX14_CONSTEXPR void eval_add(float128_backend& result, const float128_backend& a)

test/Jamfile.v2

@@ -1281,6 +1281,7 @@ test-suite misc :
       [ run git_issue_636.cpp : : : [ check-target-builds ../config//has_float128 : <source>quadmath : <build>no ] ]
       [ run git_issue_652.cpp ]
       [ run git_issue_734.cpp ]
+      [ run git_issue_743.cpp : : : [ check-target-builds ../config//has_float128 : <source>quadmath : <build>no ] ]
       [ run git_issue_759.cpp : : : [ check-target-builds ../config//has_float128 : <source>quadmath : <build>no ] ]
       [ compile git_issue_98.cpp :
          [ check-target-builds ../config//has_float128 : <define>TEST_FLOAT128 <source>quadmath : ]

test/git_issue_743.cpp

@@ -0,0 +1,22 @@
+///////////////////////////////////////////////////////////////////////////////
+//  Copyright 2026 Matt Borland. Distributed under the Boost
+//  Software License, Version 1.0. (See accompanying file
+//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+// See: https://github.com/boostorg/multiprecision/issues/743
+
+#include <boost/multiprecision/float128.hpp>
+#include "test.hpp"
+
+int main()
+{
+    using real = boost::multiprecision::float128;
+
+    constexpr real value {5};
+    BOOST_CHECK(value.backend().value() == value.backend().data());
+
+    real mutable_value {42};
+    BOOST_CHECK(mutable_value.backend().value() == mutable_value.backend().data());
+
+    return boost::report_errors();
+}