Remove dependency on Boost.Preprocessor

Closes #3050

CMakeLists.txt

@@ -67,7 +67,6 @@ set(BOOST_BEAST_DEPENDENCIES
     Boost::logic
     Boost::mp11
     Boost::optional
-    Boost::preprocessor
     Boost::smart_ptr
     Boost::static_string
     Boost::system

build.jam

@@ -20,7 +20,6 @@ constant boost_dependencies :
     /boost/logic//boost_logic
     /boost/mp11//boost_mp11
     /boost/optional//boost_optional
-    /boost/preprocessor//boost_preprocessor
     /boost/smart_ptr//boost_smart_ptr
     /boost/static_string//boost_static_string
     /boost/system//boost_system

include/boost/beast/core/detail/config.hpp

@@ -15,7 +15,6 @@
 #include <boost/version.hpp>
 #include <boost/core/ignore_unused.hpp>
 #include <boost/core/detail/static_assert.hpp>
-#include <boost/preprocessor/cat.hpp>
 
 namespace boost {
 namespace asio
@@ -102,15 +101,16 @@ namespace net = boost::asio;
 #define BOOST_BEAST_ASYNC_TPARAM2 BOOST_ASIO_COMPLETION_TOKEN_FOR(void(::boost::beast::error_code, ::std::size_t))
 #endif
 
-
 #ifdef BOOST_BEAST_NO_SOURCE_LOCATION
 #define BOOST_BEAST_ASSIGN_EC(ec, error) ec = error
 #else
-
 #define BOOST_BEAST_ASSIGN_EC(ec, error) \
-    static constexpr auto BOOST_PP_CAT(loc_, __LINE__) ((BOOST_CURRENT_LOCATION)); \
-    ec.assign(error, & BOOST_PP_CAT(loc_, __LINE__) )
-
+    do \
+    { \
+        static constexpr auto loc__((BOOST_CURRENT_LOCATION)); \
+        ec.assign(error, &loc__); \
+    } \
+    while (false)
 #endif
 
 #ifndef BOOST_BEAST_FILE_BUFFER_SIZE

test/cmake_test/CMakeLists.txt

@@ -36,7 +36,6 @@ else()
   logic
   mp11
   optional
-  preprocessor
   smart_ptr
   static_string
   system
@@ -63,6 +62,7 @@ else()
   numeric/conversion
   range
   tokenizer
+  preprocessor
   array
   concept_check
   exception