♻️ change behavior for null FILE*

docs/mkdocs/docs/api/basic_json/accept.md

@@ -29,7 +29,7 @@ Unlike the [`parse`](parse.md) function, this function neither throws an excepti
 :   A compatible input, for instance:
     
     - an `std::istream` object
-    - a `FILE` pointer
+    - a `FILE` pointer (must not be null)
     - a C-style array of characters
     - a pointer to a null-terminated string of single byte characters
     - a `std::string`
@@ -64,10 +64,6 @@ Whether the input is valid JSON.
 
 Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
 
-## Exceptions
-
-Throws [`parse_error.116`](../../home/exceptions.md#jsonexceptionparse_error116) if passed `#!cpp FILE` pointer is `#!cpp nullptr`.
-
 ## Complexity
 
 Linear in the length of the input. The parser is a predictive LL(1) parser.
@@ -76,6 +72,11 @@ Linear in the length of the input. The parser is a predictive LL(1) parser.
 
 (1) A UTF-8 byte order mark is silently ignored.
 
+!!! danger "Runtime assertion"
+
+    The precondition that a passed `#!cpp FILE` pointer must not be null is enforced with a
+    [runtime assertion](../../features/assertions.md).
+
 ## Examples
 
 ??? example

docs/mkdocs/docs/api/basic_json/parse.md

@@ -28,7 +28,7 @@ static basic_json parse(IteratorType first, IteratorType last,
 :   A compatible input, for instance:
     
     - an `std::istream` object
-    - a `FILE` pointer
+    - a `FILE` pointer (must not be null)
     - a C-style array of characters
     - a pointer to a null-terminated string of single byte characters
     - a `std::string`
@@ -77,7 +77,6 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
 - Throws [`parse_error.102`](../../home/exceptions.md#jsonexceptionparse_error102) if to_unicode fails or surrogate
   error.
 - Throws [`parse_error.103`](../../home/exceptions.md#jsonexceptionparse_error103) if to_unicode fails.
-- Throws [`parse_error.116`](../../home/exceptions.md#jsonexceptionparse_error116) if passed `#!cpp FILE` pointer is `#!cpp nullptr`.
 
 ## Complexity
 
@@ -89,6 +88,11 @@ super-linear complexity.
 
 (1) A UTF-8 byte order mark is silently ignored.
 
+!!! danger "Runtime assertion"
+
+    The precondition that a passed `#!cpp FILE` pointer must not be null is enforced with a
+    [runtime assertion](../../features/assertions.md).
+
 ## Examples
 
 ??? example "Parsing from a character array"

docs/mkdocs/docs/features/assertions.md

@@ -102,3 +102,30 @@ behavior and yields a runtime assertion.
     ```
     Assertion failed: (m_object != nullptr), function operator++, file iter_impl.hpp, line 368.
     ```
+
+### Reading from a null `FILE` pointer
+
+Reading from a null `#!cpp FILE` pointer is undefined behavior and yields a runtime assertion. This can happen when
+calling `#!cpp std::fopen` on a nonexisting file.
+
+??? example "Example 4: Uninitialized iterator"
+
+    The following code will trigger an assertion at runtime:
+
+    ```cpp
+    #include <nlohmann/json.hpp>
+
+    using json = nlohmann::json;
+
+    int main()
+    {
+      std::FILE* f = std::fopen("nonexisting_file.json", "r");
+      json j = json::parse(f);
+    }
+    ```
+
+    Output:
+
+    ```
+    Assertion failed: (m_file != nullptr), function file_input_adapter, file input_adapters.hpp, line 55.
+    ```

docs/mkdocs/docs/home/exceptions.md

@@ -354,16 +354,6 @@ A UBJSON high-precision number could not be parsed.
     [json.exception.parse_error.115] parse error at byte 5: syntax error while parsing UBJSON high-precision number: invalid number text: 1A
     ```
 
-### json.exception.parse_error.116
-
-A `#!cpp FILE` pointer passed to the [parse](../api/basic_json/parse.md) function is `#!cpp nullptr`; that is, a previous call to `#!cpp std::fopen` failed.
-
-!!! failure "Example message"
-
-    ```
-    [json.exception.parse_error.116] parse error: input file is invalid
-    ```
-
 ## Iterator errors
 
 This exception is thrown if iterators passed to a library function do not match

include/nlohmann/detail/input/input_adapters.hpp

@@ -49,13 +49,10 @@ class file_input_adapter
     using char_type = char;
 
     JSON_HEDLEY_NON_NULL(2)
-    explicit file_input_adapter(std::FILE* f)
+    explicit file_input_adapter(std::FILE* f) noexcept
         : m_file(f)
     {
-        if (m_file == nullptr)
-        {
-            JSON_THROW(parse_error::create(116, 0, "input file is invalid", nullptr));
-        }
+        JSON_ASSERT(m_file != nullptr);
     }
 
     // make class move-only
@@ -67,7 +64,11 @@ class file_input_adapter
 
     std::char_traits<char>::int_type get_character() noexcept
     {
-        return std::fgetc(m_file);
+        if (JSON_HEDLEY_LIKELY(m_file != nullptr))
+        {
+            return std::fgetc(m_file);
+        }
+        return std::char_traits<char>::eof(); // LCOV_EXCL_LINE
     }
 
   private:

single_include/nlohmann/json.hpp

@@ -5936,13 +5936,10 @@ class file_input_adapter
     using char_type = char;
 
     JSON_HEDLEY_NON_NULL(2)
-    explicit file_input_adapter(std::FILE* f)
+    explicit file_input_adapter(std::FILE* f) noexcept
         : m_file(f)
     {
-        if (m_file == nullptr)
-        {
-            JSON_THROW(parse_error::create(116, 0, "input file is invalid", nullptr));
-        }
+        JSON_ASSERT(m_file != nullptr);
     }
 
     // make class move-only
@@ -5954,7 +5951,11 @@ class file_input_adapter
 
     std::char_traits<char>::int_type get_character() noexcept
     {
-        return std::fgetc(m_file);
+        if (JSON_HEDLEY_LIKELY(m_file != nullptr))
+        {
+            return std::fgetc(m_file);
+        }
+        return std::char_traits<char>::eof(); // LCOV_EXCL_LINE
     }
 
   private:

tests/src/unit-deserialization.cpp

@@ -166,26 +166,6 @@ struct SaxEventLoggerExitAfterStartArray : public SaxEventLogger
 };
 } // namespace
 
-// Passing a NULL pointer to the input adapter violates its NON_NULL attribute which is detected by UBSAN.
-// To still test whether exceptions are thrown, we need to exclude these tests from UBSAN which can only
-// be done with a function attribute. See
-// https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html#disabling-instrumentation-with-attribute-no-sanitize-undefined
-#if defined(__clang__)
-    __attribute__((no_sanitize("undefined")))
-#endif
-void test_file_exception();
-
-#if defined(__clang__)
-    __attribute__((no_sanitize("undefined")))
-#endif
-void test_file_exception()
-{
-    std::FILE* f = std::fopen("nonexisting_file", "r"); // NOLINT(cppcoreguidelines-owning-memory)
-    json _;
-    CHECK_THROWS_WITH_AS(_ = json::parse(f), "[json.exception.parse_error.116] parse error: input file is invalid", json::parse_error&);
-    CHECK_THROWS_WITH_AS(_ = json::accept(f), "[json.exception.parse_error.116] parse error: input file is invalid", json::parse_error&);
-}
-
 TEST_CASE("deserialization")
 {
     SECTION("successful deserialization")
@@ -352,11 +332,6 @@ TEST_CASE("deserialization")
         {
             CHECK_THROWS_WITH_AS("[\"foo\",1,2,3,false,{\"one\":1}"_json, "[json.exception.parse_error.101] parse error at line 1, column 29: syntax error while parsing array - unexpected end of input; expected ']'", json::parse_error&);
         }
-
-        SECTION("FILE*")
-        {
-            test_file_exception();
-        }
     }
 
     SECTION("contiguous containers")