📝 update documentation

README.md

@@ -1648,7 +1648,7 @@ Here is a related issue [#1924](https://github.com/nlohmann/json/issues/1924).
 - The code contains numerous debug **assertions** which can be switched off by defining the preprocessor macro `NDEBUG`, see the [documentation of `assert`](https://en.cppreference.com/w/cpp/error/assert). In particular, note [`operator[]`](https://nlohmann.github.io/json/api/basic_json/operator%5B%5D/) implements **unchecked access** for const objects: If the given key is not present, the behavior is undefined (think of a dereferenced null pointer) and yields an [assertion failure](https://github.com/nlohmann/json/issues/289) if assertions are switched on. If you are not sure whether an element in an object exists, use checked access with the [`at()` function](https://nlohmann.github.io/json/api/basic_json/at/). Furthermore, you can define `JSON_ASSERT(x)` to replace calls to `assert(x)`.
 - As the exact type of a number is not defined in the [JSON specification](https://tools.ietf.org/html/rfc8259.html), this library tries to choose the best fitting C++ number type automatically. As a result, the type `double` may be used to store numbers which may yield [**floating-point exceptions**](https://github.com/nlohmann/json/issues/181) in certain rare situations if floating-point exceptions have been unmasked in the calling code. These exceptions are not caused by the library and need to be fixed in the calling code, such as by re-masking the exceptions prior to calling library functions.
 - The code can be compiled without C++ **runtime type identification** features; that is, you can use the `-fno-rtti` compiler flag.
-- **Exceptions** are used widely within the library. They can, however, be switched off with either using the compiler flag `-fno-exceptions` or by defining the symbol `JSON_NOEXCEPTION`. In this case, exceptions are replaced by `abort()` calls. You can further control this behavior by defining `JSON_THROW_USER` (overriding `throw`), `JSON_TRY_USER` (overriding `try`), and `JSON_CATCH_USER` (overriding `catch`). Note that `JSON_THROW_USER` should leave the current scope (e.g., by throwing or aborting), as continuing after it may yield undefined behavior.
+- **Exceptions** are used widely within the library. They can, however, be switched off with either using the compiler flag `-fno-exceptions` or by defining the symbol `JSON_NOEXCEPTION`. In this case, exceptions are replaced by `abort()` calls. You can further control this behavior by defining `JSON_THROW_USER` (overriding `throw`), `JSON_TRY_USER` (overriding `try`), and `JSON_CATCH_USER` (overriding `catch`). Note that `JSON_THROW_USER` should leave the current scope (e.g., by throwing or aborting), as continuing after it may yield undefined behavior. Note the explanatory [`what()`](https://en.cppreference.com/w/cpp/error/exception/what) string of exceptions is not available for MSVC if exceptions are disabled, see [#2824](https://github.com/nlohmann/json/discussions/2824).
 
 ## Execute unit tests
 

doc/mkdocs/docs/features/macros.md

@@ -32,6 +32,8 @@ When defining `JSON_NOEXCEPTION`, `#!cpp try` is replaced by `#!cpp if (true)`,
 
 The same effect is achieved by setting the compiler flag `-fno-exceptions`.
 
+Note the explanatory [`what()`](https://en.cppreference.com/w/cpp/error/exception/what) string of exceptions is not available for MSVC if exceptions are disabled, see [#2824](https://github.com/nlohmann/json/discussions/2824).
+
 ## `JSON_NO_IO`
 
 When defined, headers `<cstdio>`, `<ios>`, `<iosfwd>`, `<istream>`, and `<ostream>` are not included and parse functions relying on these headers are excluded. This is relevant for environment where these I/O functions are disallowed for security reasons (e.g., Intel Software Guard Extensions (SGX)).

doc/mkdocs/docs/home/exceptions.md

@@ -50,6 +50,8 @@ Note that `JSON_THROW_USER` should leave the current scope (e.g., by throwing or
     #include <nlohmann/json.hpp>
     ```
 
+Note the explanatory [`what()`](https://en.cppreference.com/w/cpp/error/exception/what) string of exceptions is not available for MSVC if exceptions are disabled, see [#2824](https://github.com/nlohmann/json/discussions/2824).
+
 ### Extended diagnostic messages
 
 Exceptions in the library are thrown in the local context of the JSON value they are detected. This makes detailed diagnostics messages, and hence debugging, difficult.

test/CMakeLists.txt

@@ -95,8 +95,9 @@ target_compile_definitions(test-disabled_exceptions PUBLIC JSON_NOEXCEPTION)
 if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang" OR CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang" OR CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
     target_compile_options(test-disabled_exceptions PUBLIC -fno-exceptions)
 elseif (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
-    target_compile_options(test-disabled_exceptions PUBLIC /EH)
-    target_compile_definitions(test-disabled_exceptions PUBLIC _HAS_EXCEPTIONS=0)
+    # disabled due to https://github.com/nlohmann/json/discussions/2824
+    #target_compile_options(test-disabled_exceptions PUBLIC /EH)
+    #target_compile_definitions(test-disabled_exceptions PUBLIC _HAS_EXCEPTIONS=0)
 endif()
 
 add_executable(json_unit EXCLUDE_FROM_ALL $<TARGET_OBJECTS:doctest_main> ${files})

test/src/unit-disabled_exceptions.cpp

@@ -52,48 +52,6 @@ class sax_no_exception : public nlohmann::detail::json_sax_dom_parser<json>
 
 std::string* sax_no_exception::error_string = nullptr;
 
-//
-#include <exception> // exception
-#include <stdexcept> // runtime_error
-
-//
-namespace nlohmann
-{
-namespace detail2
-{
-
-class exception : public std::exception
-{
-  public:
-    const char* what() const noexcept override
-    {
-        return m.what();
-    }
-
-  protected:
-    exception(const char* what_arg) : m(what_arg) {}
-
-  private:
-    std::runtime_error m;
-};
-
-class parse_error : public exception
-{
-  public:
-    static parse_error create(const std::string& what_arg)
-    {
-        std::string w = "[json.exception.parse_error] " + what_arg;
-        return parse_error(w.c_str());
-    }
-
-  private:
-    parse_error(const char* what_arg) : exception(what_arg) {}
-};
-
-}  // namespace detail2
-}  // namespace nlohmann
-//
-
 TEST_CASE("Tests with disabled exceptions")
 {
     SECTION("issue #2824 - encoding of json::exception::what()")
@@ -102,13 +60,7 @@ TEST_CASE("Tests with disabled exceptions")
         sax_no_exception sax(j);
 
         CHECK (!json::sax_parse("xyz", &sax));
-        //CHECK(*sax_no_exception::error_string == "[json.exception.parse_error.101] parse error at line 1, column 1: syntax error while parsing value - invalid literal; last read: 'x'");
+        CHECK(*sax_no_exception::error_string == "[json.exception.parse_error.101] parse error at line 1, column 1: syntax error while parsing value - invalid literal; last read: 'x'");
         delete sax_no_exception::error_string; // NOLINT(cppcoreguidelines-owning-memory)
     }
-
-    SECTION("test")
-    {
-        auto error = nlohmann::detail2::parse_error::create("foo");
-        CHECK(std::string(error.what()) == "[json.exception.parse_error] foo");
-    }
 }