Make JSON_STRICT_NUL_HANDLING part of the ABI tag

JSON_STRICT_NUL_HANDLING (#5534) changes the bodies of inline functions:
the lexer's handling of '\0' and input_adapter() for char arrays. So
translation units compiled with and without it define the same functions
differently, an ODR violation - the case the ABI tag exists for, as with
JSON_BRACE_INIT_COPY_SEMANTICS (_bics). It now appends _snul to the inline
namespace. The macro is new in 3.13.0, so no existing namespace changes.

Its default moves to abi_macros.hpp, and it is only #undef'd without
JSON_TEST_KEEP_MACROS, as for the other ABI macros. The ABI config tests,
the namespace docs, the macro's docs and the Natvis file cover the new tag.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

docs/mkdocs/docs/api/macros/json_strict_nul_handling.md

@@ -65,6 +65,12 @@ The default value is `0` (disabled — existing behavior is preserved).
     for CBOR or MessagePack, are never affected by this trimming; their full extent - including a genuine trailing
     `0x00` - is always preserved, in both states of this macro.
 
+!!! note "ABI compatibility"
+
+    The value of this macro is encoded in the [namespace](../../features/namespace.md) (tag `_snul`), resulting in
+    distinct symbol names. Translation units compiled with and without it can therefore be linked into the same program
+    without One Definition Rule (ODR) violations, but they cannot exchange instances of library types.
+
 !!! tip "Workaround without the macro"
 
     To reject a NUL byte without enabling this macro, trim your input yourself before calling `parse()`:

docs/mkdocs/docs/features/namespace.md

@@ -18,6 +18,7 @@ The complete default namespace name is derived as follows:
     - [`JSON_DIAGNOSTIC_POSITIONS`](../api/macros/json_diagnostic_positions.md) defined non-zero appends `_dp`.
     - [`JSON_BRACE_INIT_COPY_SEMANTICS`](../api/macros/json_brace_init_copy_semantics.md) defined non-zero appends
       `_bics`.
+    - [`JSON_STRICT_NUL_HANDLING`](../api/macros/json_strict_nul_handling.md) defined non-zero appends `_snul`.
 - The inline namespace ends with the suffix `_v` followed by the 3 components of the version number separated by
   underscores. To omit the version component, see [Disabling the version component](#disabling-the-version-component)
   below.

include/nlohmann/detail/abi_macros.hpp

@@ -38,6 +38,10 @@
     #define JSON_BRACE_INIT_COPY_SEMANTICS 0
 #endif
 
+#ifndef JSON_STRICT_NUL_HANDLING
+    #define JSON_STRICT_NUL_HANDLING 0
+#endif
+
 #if JSON_DIAGNOSTICS
     #define NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS _diag
 #else
@@ -62,21 +66,28 @@
     #define NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS
 #endif
 
+#if JSON_STRICT_NUL_HANDLING
+    #define NLOHMANN_JSON_ABI_TAG_STRICT_NUL_HANDLING _snul
+#else
+    #define NLOHMANN_JSON_ABI_TAG_STRICT_NUL_HANDLING
+#endif
+
 #ifndef NLOHMANN_JSON_NAMESPACE_NO_VERSION
     #define NLOHMANN_JSON_NAMESPACE_NO_VERSION 0
 #endif
 
 // Construct the namespace ABI tags component
-#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d) json_abi ## a ## b ## c ## d
-#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d) \
-    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d)
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e) json_abi ## a ## b ## c ## d ## e
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d, e) \
+    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e)
 
 #define NLOHMANN_JSON_ABI_TAGS                                       \
     NLOHMANN_JSON_ABI_TAGS_CONCAT(                                   \
             NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS,                       \
             NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON, \
             NLOHMANN_JSON_ABI_TAG_DIAGNOSTIC_POSITIONS,              \
-            NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS)
+            NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS,         \
+            NLOHMANN_JSON_ABI_TAG_STRICT_NUL_HANDLING)
 
 // Construct the namespace version component
 #define NLOHMANN_JSON_NAMESPACE_VERSION_CONCAT_EX(major, minor, patch) \

include/nlohmann/detail/macro_scope.hpp

@@ -812,7 +812,3 @@ void templated_json_throw(ExceptionType exception)
 #ifndef JSON_USE_GLOBAL_UDLS
     #define JSON_USE_GLOBAL_UDLS 1
 #endif
-
-#ifndef JSON_STRICT_NUL_HANDLING
-    #define JSON_STRICT_NUL_HANDLING 0
-#endif

include/nlohmann/detail/macro_unscope.hpp

@@ -26,7 +26,6 @@
 #undef JSON_NO_UNIQUE_ADDRESS
 #undef JSON_DISABLE_ENUM_SERIALIZATION
 #undef JSON_USE_GLOBAL_UDLS
-#undef JSON_STRICT_NUL_HANDLING
 
 #ifndef JSON_TEST_KEEP_MACROS
     #undef JSON_CATCH
@@ -45,6 +44,7 @@
     #undef JSON_HAS_STATIC_RTTI
     #undef JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
     #undef JSON_BRACE_INIT_COPY_SEMANTICS
+    #undef JSON_STRICT_NUL_HANDLING
 #endif
 
 #include <nlohmann/thirdparty/hedley/hedley_undef.hpp>

single_include/nlohmann/json.hpp

@@ -95,6 +95,10 @@
     #define JSON_BRACE_INIT_COPY_SEMANTICS 0
 #endif
 
+#ifndef JSON_STRICT_NUL_HANDLING
+    #define JSON_STRICT_NUL_HANDLING 0
+#endif
+
 #if JSON_DIAGNOSTICS
     #define NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS _diag
 #else
@@ -119,21 +123,28 @@
     #define NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS
 #endif
 
+#if JSON_STRICT_NUL_HANDLING
+    #define NLOHMANN_JSON_ABI_TAG_STRICT_NUL_HANDLING _snul
+#else
+    #define NLOHMANN_JSON_ABI_TAG_STRICT_NUL_HANDLING
+#endif
+
 #ifndef NLOHMANN_JSON_NAMESPACE_NO_VERSION
     #define NLOHMANN_JSON_NAMESPACE_NO_VERSION 0
 #endif
 
 // Construct the namespace ABI tags component
-#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d) json_abi ## a ## b ## c ## d
-#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d) \
-    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d)
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e) json_abi ## a ## b ## c ## d ## e
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d, e) \
+    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e)
 
 #define NLOHMANN_JSON_ABI_TAGS                                       \
     NLOHMANN_JSON_ABI_TAGS_CONCAT(                                   \
             NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS,                       \
             NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON, \
             NLOHMANN_JSON_ABI_TAG_DIAGNOSTIC_POSITIONS,              \
-            NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS)
+            NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS,         \
+            NLOHMANN_JSON_ABI_TAG_STRICT_NUL_HANDLING)
 
 // Construct the namespace version component
 #define NLOHMANN_JSON_NAMESPACE_VERSION_CONCAT_EX(major, minor, patch) \
@@ -3202,10 +3213,6 @@ void templated_json_throw(ExceptionType exception)
     #define JSON_USE_GLOBAL_UDLS 1
 #endif
 
-#ifndef JSON_STRICT_NUL_HANDLING
-    #define JSON_STRICT_NUL_HANDLING 0
-#endif
-
 #if JSON_HAS_THREE_WAY_COMPARISON
     #include <compare> // partial_ordering
 #endif
@@ -30426,7 +30433,6 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c
 #undef JSON_NO_UNIQUE_ADDRESS
 #undef JSON_DISABLE_ENUM_SERIALIZATION
 #undef JSON_USE_GLOBAL_UDLS
-#undef JSON_STRICT_NUL_HANDLING
 
 #ifndef JSON_TEST_KEEP_MACROS
     #undef JSON_CATCH
@@ -30445,6 +30451,7 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c
     #undef JSON_HAS_STATIC_RTTI
     #undef JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
     #undef JSON_BRACE_INIT_COPY_SEMANTICS
+    #undef JSON_STRICT_NUL_HANDLING
 #endif
 
 // #include <nlohmann/thirdparty/hedley/hedley_undef.hpp>

single_include/nlohmann/json_fwd.hpp

@@ -56,6 +56,10 @@
     #define JSON_BRACE_INIT_COPY_SEMANTICS 0
 #endif
 
+#ifndef JSON_STRICT_NUL_HANDLING
+    #define JSON_STRICT_NUL_HANDLING 0
+#endif
+
 #if JSON_DIAGNOSTICS
     #define NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS _diag
 #else
@@ -80,21 +84,28 @@
     #define NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS
 #endif
 
+#if JSON_STRICT_NUL_HANDLING
+    #define NLOHMANN_JSON_ABI_TAG_STRICT_NUL_HANDLING _snul
+#else
+    #define NLOHMANN_JSON_ABI_TAG_STRICT_NUL_HANDLING
+#endif
+
 #ifndef NLOHMANN_JSON_NAMESPACE_NO_VERSION
     #define NLOHMANN_JSON_NAMESPACE_NO_VERSION 0
 #endif
 
 // Construct the namespace ABI tags component
-#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d) json_abi ## a ## b ## c ## d
-#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d) \
-    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d)
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e) json_abi ## a ## b ## c ## d ## e
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d, e) \
+    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e)
 
 #define NLOHMANN_JSON_ABI_TAGS                                       \
     NLOHMANN_JSON_ABI_TAGS_CONCAT(                                   \
             NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS,                       \
             NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON, \
             NLOHMANN_JSON_ABI_TAG_DIAGNOSTIC_POSITIONS,              \
-            NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS)
+            NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS,         \
+            NLOHMANN_JSON_ABI_TAG_STRICT_NUL_HANDLING)
 
 // Construct the namespace version component
 #define NLOHMANN_JSON_NAMESPACE_VERSION_CONCAT_EX(major, minor, patch) \

tests/abi/config/default.cpp

@@ -36,6 +36,10 @@ TEST_CASE("default namespace")
         expected += "_bics";
 #endif
 
+#if JSON_STRICT_NUL_HANDLING
+        expected += "_snul";
+#endif
+
         expected += "_v" STRINGIZE(NLOHMANN_JSON_VERSION_MAJOR);
         expected += "_" STRINGIZE(NLOHMANN_JSON_VERSION_MINOR);
         expected += "_" STRINGIZE(NLOHMANN_JSON_VERSION_PATCH) "::basic_json";

tests/abi/config/noversion.cpp

@@ -37,6 +37,10 @@ TEST_CASE("default namespace without version component")
         expected += "_bics";
 #endif
 
+#if JSON_STRICT_NUL_HANDLING
+        expected += "_snul";
+#endif
+
         expected += "::basic_json";
 
         // fallback for Clang

tests/src/unit-class_parser.cpp

@@ -11,11 +11,15 @@
 // capture whether JSON_STRICT_NUL_HANDLING was enabled on the command line
 // (e.g. -DJSON_STRICT_NUL_HANDLING=1) *before* including json.hpp, since the
 // library #undefs JSON_STRICT_NUL_HANDLING itself once the header has been
-// fully processed (see include/nlohmann/detail/macro_unscope.hpp)
+// fully processed unless JSON_TEST_KEEP_MACROS is defined (see
+// include/nlohmann/detail/macro_unscope.hpp)
 #if defined(JSON_STRICT_NUL_HANDLING) && (JSON_STRICT_NUL_HANDLING == 1)
     #define JSON_TEST_STRICT_NUL_HANDLING_ENABLED 1
 #endif
 
+#define JSON_TEST_STRINGIZE_EX(x) #x
+#define JSON_TEST_STRINGIZE(x) JSON_TEST_STRINGIZE_EX(x)
+
 #define JSON_TESTS_PRIVATE
 #include <nlohmann/json.hpp>
 using nlohmann::json;
@@ -566,6 +570,16 @@ TEST_CASE("parser class")
             // left at its default or forced to 1 (e.g. by the dedicated
             // ci_test_strict_nul_handling CI target), so only the section
             // matching the actual, compiled-in behavior can pass.
+            SECTION("the macro is part of the ABI tag")
+            {
+                const std::string ns = JSON_TEST_STRINGIZE(NLOHMANN_JSON_NAMESPACE);
+#if defined(JSON_TEST_STRICT_NUL_HANDLING_ENABLED)
+                CHECK(ns.find("_snul") != std::string::npos);
+#else
+                CHECK(ns.find("_snul") == std::string::npos);
+#endif
+            }
+
 #if !defined(JSON_TEST_STRICT_NUL_HANDLING_ENABLED)
             SECTION("default behavior (macro not enabled)")
             {

tools/generate_natvis/generate_natvis.py

@@ -20,7 +20,7 @@ if __name__ == '__main__':
 
     namespaces = ['nlohmann']
     abi_prefix = 'json_abi'
-    abi_tags = ['_diag', '_ldvcmp', '_dp', '_bics']
+    abi_tags = ['_diag', '_ldvcmp', '_dp', '_bics', '_snul']
     version = '_v' + args.version.replace('.', '_')
     inline_namespaces = []