diff --git a/base/poco/Foundation/include/Poco/Alignment.h b/base/poco/Foundation/include/Poco/Alignment.h
index b1d48ffd62d..300c55ee8ef 100644
--- a/base/poco/Foundation/include/Poco/Alignment.h
+++ b/base/poco/Foundation/include/Poco/Alignment.h
@@ -136,7 +136,6 @@ struct AlignedCharArrayImpl;
 
 // MSVC requires special handling here.
 
-#        ifdef POCO_COMPILER_CLANG
 
 #            if __has_feature(cxx_alignas)
 #                define POCO_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(x) \
@@ -148,17 +147,6 @@ struct AlignedCharArrayImpl;
 #                define POCO_HAVE_ALIGNMENT
 #            endif
 
-#        elif defined(__GNUC__) || defined(__IBM_ATTRIBUTES)
-
-#            define POCO_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(x) \
-                template <> \
-                struct AlignedCharArrayImpl<x> \
-                { \
-                    char aligned __attribute__((aligned(x))); \
-                }
-#            define POCO_HAVE_ALIGNMENT
-
-#        endif
 
 #        ifdef POCO_HAVE_ALIGNMENT
 POCO_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(1);
diff --git a/base/poco/Foundation/include/Poco/ByteOrder.h b/base/poco/Foundation/include/Poco/ByteOrder.h
index 09f673c2718..a8abf09f93b 100644
--- a/base/poco/Foundation/include/Poco/ByteOrder.h
+++ b/base/poco/Foundation/include/Poco/ByteOrder.h
@@ -82,11 +82,7 @@ public:
 
 
 #if !defined(POCO_NO_BYTESWAP_BUILTINS)
-#    if   defined(__clang__)
-#        if __has_builtin(__builtin_bswap32)
-#            define POCO_HAVE_GCC_BYTESWAP 1
-#        endif
-#    elif defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3))
+#    if __has_builtin(__builtin_bswap32)
 #        define POCO_HAVE_GCC_BYTESWAP 1
 #    endif
 #endif
diff --git a/base/poco/Foundation/include/Poco/Foundation.h b/base/poco/Foundation/include/Poco/Foundation.h
index 34493041720..bee9d9d90a9 100644
--- a/base/poco/Foundation/include/Poco/Foundation.h
+++ b/base/poco/Foundation/include/Poco/Foundation.h
@@ -98,10 +98,8 @@
 #    define POCO_DEPRECATED
 #elif defined(_GNUC_)
 #    define POCO_DEPRECATED __attribute__((deprecated))
-#elif defined(__clang__)
-#    define POCO_DEPRECATED __attribute__((deprecated))
 #else
-#    define POCO_DEPRECATED
+#    define POCO_DEPRECATED __attribute__((deprecated))
 #endif
 
 
diff --git a/base/poco/Foundation/include/Poco/Platform.h b/base/poco/Foundation/include/Poco/Platform.h
index eb8f80a0d25..fe45833aea6 100644
--- a/base/poco/Foundation/include/Poco/Platform.h
+++ b/base/poco/Foundation/include/Poco/Platform.h
@@ -212,25 +212,6 @@
 #endif
 
 
-#if defined(__clang__)
-#    define POCO_COMPILER_CLANG
-#elif defined(__GNUC__)
-#    define POCO_COMPILER_GCC
-#elif defined(__MINGW32__) || defined(__MINGW64__)
-#    define POCO_COMPILER_MINGW
-#elif defined(__INTEL_COMPILER) || defined(__ICC) || defined(__ECC) || defined(__ICL)
-#    define POCO_COMPILER_INTEL
-#elif defined(__MWERKS__) || defined(__CWCC__)
-#    define POCO_COMPILER_CODEWARRIOR
-#elif defined(__sgi) || defined(sgi)
-#    define POCO_COMPILER_SGI
-#elif defined(__BORLANDC__) || defined(__CODEGEARC__)
-#    define POCO_COMPILER_CBUILDER
-#elif defined(__DMC__)
-#    define POCO_COMPILER_DMARS
-#endif
-
-
 #ifdef __GNUC__
 #    define POCO_UNUSED __attribute__((unused))
 #else
diff --git a/base/poco/Foundation/include/Poco/Platform_POSIX.h b/base/poco/Foundation/include/Poco/Platform_POSIX.h
index 96f0c32cb9e..b23c6d68b90 100644
--- a/base/poco/Foundation/include/Poco/Platform_POSIX.h
+++ b/base/poco/Foundation/include/Poco/Platform_POSIX.h
@@ -32,10 +32,8 @@
 //
 // Thread-safety of local static initialization
 //
-#if __cplusplus >= 201103L || __GNUC__ >= 4 || defined(__clang__)
-#    ifndef POCO_LOCAL_STATIC_INIT_IS_THREADSAFE
-#        define POCO_LOCAL_STATIC_INIT_IS_THREADSAFE 1
-#    endif
+#ifndef POCO_LOCAL_STATIC_INIT_IS_THREADSAFE
+#    define POCO_LOCAL_STATIC_INIT_IS_THREADSAFE 1
 #endif
 
 
diff --git a/base/poco/Foundation/include/Poco/Types.h b/base/poco/Foundation/include/Poco/Types.h
index d10047344f6..4f4924a2542 100644
--- a/base/poco/Foundation/include/Poco/Types.h
+++ b/base/poco/Foundation/include/Poco/Types.h
@@ -25,7 +25,6 @@ namespace Poco
 {
 
 
-#if   defined(__GNUC__) || defined(__clang__)
 //
 // Unix/GCC/Clang
 //
@@ -46,7 +45,6 @@ typedef unsigned long UInt64;
 typedef signed long long Int64;
 typedef unsigned long long UInt64;
 #        endif
-#endif
 
 
 } // namespace Poco
diff --git a/base/poco/Net/include/Poco/Net/HTTPRequest.h b/base/poco/Net/include/Poco/Net/HTTPRequest.h
index 7f17342b22d..269167feb83 100644
--- a/base/poco/Net/include/Poco/Net/HTTPRequest.h
+++ b/base/poco/Net/include/Poco/Net/HTTPRequest.h
@@ -132,14 +132,10 @@ namespace Net
         /// Writes the HTTP request to the given
         /// output stream.
 
-#if __clang__
 #    pragma clang diagnostic push
 #    pragma clang diagnostic ignored "-Woverloaded-virtual"
-#endif
         void read(std::istream & istr);
-#if __clang__
 #    pragma clang diagnostic pop
-#endif
 
         /// Reads the HTTP request from the
         /// given input stream.
diff --git a/base/poco/Net/include/Poco/Net/HTTPResponse.h b/base/poco/Net/include/Poco/Net/HTTPResponse.h
index b889f0b30fb..3c444c3d38c 100644
--- a/base/poco/Net/include/Poco/Net/HTTPResponse.h
+++ b/base/poco/Net/include/Poco/Net/HTTPResponse.h
@@ -188,14 +188,10 @@ namespace Net
         /// Writes the HTTP response to the given
         /// output stream, but do not finish with \r\n delimiter.
 
-#if __clang__
 #    pragma clang diagnostic push
 #    pragma clang diagnostic ignored "-Woverloaded-virtual"
-#endif
         void read(std::istream & istr);
-#if __clang__
 #    pragma clang diagnostic pop
-#endif
         /// Reads the HTTP response from the
         /// given input stream.
         ///