🔨 added macro to disable compiler check #1128

README.md

@@ -820,6 +820,8 @@ Please note:
 
 - For GCC running on MinGW or Android SDK, the error `'to_string' is not a member of 'std'` (or similarly, for `strtod`) may occur. Note this is not an issue with the code,  but rather with the compiler itself. On Android, see above to build with a newer environment.  For MinGW, please refer to [this site](http://tehsausage.com/mingw-to-string) and [this discussion](https://github.com/nlohmann/json/issues/136) for information on how to fix this bug. For Android NDK using `APP_STL := gnustl_static`, please refer to [this discussion](https://github.com/nlohmann/json/issues/219).
 
+- Unsupported versions of GCC and Clang are rejected by `#error` directives. This can be switched off by defining `JSON_SKIP_UNSUPPORTED_COMPILER_CHECK`. Note that you can expect no support in this case.
+
 The following compilers are currently used in continuous integration at [Travis](https://travis-ci.org/nlohmann/json) and [AppVeyor](https://ci.appveyor.com/project/nlohmann/json):
 
 | Compiler        | Operating System             | Version String |

include/nlohmann/detail/macro_scope.hpp

@@ -4,14 +4,16 @@
 // You MUST include macro_unscope.hpp at the end of json.hpp to undef all of them
 
 // exclude unsupported compilers
-#if defined(__clang__)
+#if !defined(JSON_SKIP_UNSUPPORTED_COMPILER_CHECK)
+    #if defined(__clang__)
         #if (__clang_major__ * 10000 + __clang_minor__ * 100 + __clang_patchlevel__) < 30400
             #error "unsupported Clang version - see https://github.com/nlohmann/json#supported-compilers"
         #endif
-#elif defined(__GNUC__) && !(defined(__ICC) || defined(__INTEL_COMPILER))
+    #elif defined(__GNUC__) && !(defined(__ICC) || defined(__INTEL_COMPILER))
         #if (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__) < 40900
             #error "unsupported GCC version - see https://github.com/nlohmann/json#supported-compilers"
         #endif
+    #endif
 #endif
 
 // disable float-equal warnings on GCC/clang

single_include/nlohmann/json.hpp

@@ -119,14 +119,16 @@ using json = basic_json<>;
 // You MUST include macro_unscope.hpp at the end of json.hpp to undef all of them
 
 // exclude unsupported compilers
-#if defined(__clang__)
+#if !defined(JSON_SKIP_UNSUPPORTED_COMPILER_CHECK)
+    #if defined(__clang__)
         #if (__clang_major__ * 10000 + __clang_minor__ * 100 + __clang_patchlevel__) < 30400
             #error "unsupported Clang version - see https://github.com/nlohmann/json#supported-compilers"
         #endif
-#elif defined(__GNUC__) && !(defined(__ICC) || defined(__INTEL_COMPILER))
+    #elif defined(__GNUC__) && !(defined(__ICC) || defined(__INTEL_COMPILER))
         #if (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__) < 40900
             #error "unsupported GCC version - see https://github.com/nlohmann/json#supported-compilers"
         #endif
+    #endif
 #endif
 
 // disable float-equal warnings on GCC/clang