Refuse to build the fuzzer drivers with NDEBUG (#5562)

The fuzzer drivers check their round trips with assert(), which NDEBUG
compiles away. The OSS-Fuzz build keeps assertions on today, but nothing
pins that: a build change that adds NDEBUG would silently turn every
round-trip check into a mere "does not crash" check. Each driver now
stops the build with an #error instead, and includes <cassert> itself
rather than relying on json.hpp.

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

tests/src/fuzzer-parse_bjdata.cpp

@@ -46,10 +46,16 @@ The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */
 
+#include <cassert>
 #include <iostream>
 #include <sstream>
 #include <nlohmann/json.hpp>
 
+// the round-trip checks below are assertions; NDEBUG would compile them away
+#ifdef NDEBUG
+    #error "the fuzzer drivers must be built without NDEBUG"
+#endif
+
 using json = nlohmann::json;
 
 // value-stable comparison for the round-trip checks below; see the note

tests/src/fuzzer-parse_bson.cpp

@@ -19,10 +19,16 @@ The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */
 
+#include <cassert>
 #include <iostream>
 #include <sstream>
 #include <nlohmann/json.hpp>
 
+// the round-trip checks below are assertions; NDEBUG would compile them away
+#ifdef NDEBUG
+    #error "the fuzzer drivers must be built without NDEBUG"
+#endif
+
 using json = nlohmann::json;
 
 // see http://llvm.org/docs/LibFuzzer.html

tests/src/fuzzer-parse_cbor.cpp

@@ -19,10 +19,16 @@ The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */
 
+#include <cassert>
 #include <iostream>
 #include <sstream>
 #include <nlohmann/json.hpp>
 
+// the round-trip checks below are assertions; NDEBUG would compile them away
+#ifdef NDEBUG
+    #error "the fuzzer drivers must be built without NDEBUG"
+#endif
+
 using json = nlohmann::json;
 
 // see http://llvm.org/docs/LibFuzzer.html

tests/src/fuzzer-parse_json.cpp

@@ -20,10 +20,16 @@ The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */
 
+#include <cassert>
 #include <iostream>
 #include <sstream>
 #include <nlohmann/json.hpp>
 
+// the round-trip checks below are assertions; NDEBUG would compile them away
+#ifdef NDEBUG
+    #error "the fuzzer drivers must be built without NDEBUG"
+#endif
+
 using json = nlohmann::json;
 
 // see http://llvm.org/docs/LibFuzzer.html

tests/src/fuzzer-parse_msgpack.cpp

@@ -19,10 +19,16 @@ The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */
 
+#include <cassert>
 #include <iostream>
 #include <sstream>
 #include <nlohmann/json.hpp>
 
+// the round-trip checks below are assertions; NDEBUG would compile them away
+#ifdef NDEBUG
+    #error "the fuzzer drivers must be built without NDEBUG"
+#endif
+
 using json = nlohmann::json;
 
 // see http://llvm.org/docs/LibFuzzer.html

tests/src/fuzzer-parse_ubjson.cpp

@@ -25,10 +25,16 @@ The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */
 
+#include <cassert>
 #include <iostream>
 #include <sstream>
 #include <nlohmann/json.hpp>
 
+// the round-trip checks below are assertions; NDEBUG would compile them away
+#ifdef NDEBUG
+    #error "the fuzzer drivers must be built without NDEBUG"
+#endif
+
 using json = nlohmann::json;
 
 // see http://llvm.org/docs/LibFuzzer.html