Merge bitcoin/bitcoin#27919: ci: Run fuzz target even if input folder is empty

0000f55293 ci: Run fuzz target even if input folder is empty (MarcoFalke)

Pull request description:

  This should catch trivial integer sanitizer bugs if the author and all reviewers forget to look for them.

ACKs for top commit:
  brunoerg:
    reACK 0000f55293
  dergoegge:
    reACK 0000f55293

Tree-SHA512: f139b9d56f0cf1aae339c2890721c77c88d1fea77b73d492c1386ec99b4f393c5b664029919ff4a22e4e8a2929f085699a148c6acc2cc3e40df8a72fd39ff474

ci/test/06_script_b.sh

@@ -170,5 +170,5 @@ if [ "${RUN_TIDY}" = "true" ]; then
 fi
 
 if [ "$RUN_FUZZ_TESTS" = "true" ]; then
-  bash -c "LD_LIBRARY_PATH=${DEPENDS_DIR}/${HOST}/lib test/fuzz/test_runner.py ${FUZZ_TESTS_CONFIG} $MAKEJOBS -l DEBUG ${DIR_FUZZ_IN}"
+  bash -c "LD_LIBRARY_PATH=${DEPENDS_DIR}/${HOST}/lib test/fuzz/test_runner.py ${FUZZ_TESTS_CONFIG} $MAKEJOBS -l DEBUG ${DIR_FUZZ_IN} --empty_min_time=60"
 fi

test/fuzz/test_runner.py

@@ -6,6 +6,7 @@
 """
 
 from concurrent.futures import ThreadPoolExecutor, as_completed
+from pathlib import Path
 import argparse
 import configparser
 import logging
@@ -41,6 +42,11 @@ def main():
         action='store_true',
         help='If true, run fuzzing binaries under the valgrind memory error detector',
     )
+    parser.add_argument(
+        "--empty_min_time",
+        type=int,
+        help="If set, run at least this long, if the existing fuzz inputs directory is empty.",
+    )
     parser.add_argument(
         '-x',
         '--exclude',
@@ -76,6 +82,7 @@ def main():
     )
 
     args = parser.parse_args()
+    args.corpus_dir = Path(args.corpus_dir)
 
     # Set up logging
     logging.basicConfig(
@@ -180,6 +187,7 @@ def main():
             src_dir=config['environment']['SRCDIR'],
             build_dir=config["environment"]["BUILDDIR"],
             use_valgrind=args.valgrind,
+            empty_min_time=args.empty_min_time,
         )
 
 
@@ -251,16 +259,22 @@ def merge_inputs(*, fuzz_pool, corpus, test_list, src_dir, build_dir, merge_dir)
         future.result()
 
 
-def run_once(*, fuzz_pool, corpus, test_list, src_dir, build_dir, use_valgrind):
+def run_once(*, fuzz_pool, corpus, test_list, src_dir, build_dir, use_valgrind, empty_min_time):
     jobs = []
     for t in test_list:
-        corpus_path = os.path.join(corpus, t)
+        corpus_path = corpus / t
         os.makedirs(corpus_path, exist_ok=True)
         args = [
             os.path.join(build_dir, 'src', 'test', 'fuzz', 'fuzz'),
-            '-runs=1',
-            corpus_path,
         ]
+        empty_dir = not any(corpus_path.iterdir())
+        if empty_min_time and empty_dir:
+            args += [f"-max_total_time={empty_min_time}"]
+        else:
+            args += [
+                "-runs=1",
+                corpus_path,
+            ]
         if use_valgrind:
             args = ['valgrind', '--quiet', '--error-exitcode=1'] + args