Change JCC error log location and upload (google#11789)

Upload `JCC`'s error log to assist `OSS-Fuzz-Gen` analyzing and
classifying build errors:
1. Change JCC `err.log` location, because`/out` was removed before
`compile` by default and `err.log` cannot be saved there.
2. Add a step in `target_experiment.py` to upload `err.log` to gcloud
bucket.

---------

Co-authored-by: Jim Choi <[email protected]>

Author: cjx10

infra/base-images/base-builder/jcc/jcc.go

@@ -357,7 +357,7 @@ func WriteStdErrOut(outstr string, errstr string) {
 	// Prints |outstr| to stdout, prints |errstr| to stderr, and saves |errstr| to err.log.
 	fmt.Print(outstr)
 	fmt.Fprint(os.Stderr, errstr)
-	AppendStringToFile("/out/err.log", errstr)
+	AppendStringToFile("/workspace/err.log", errstr)
 }
 
 func main() {

infra/build/functions/target_experiment.py

@@ -28,7 +28,7 @@
 JCC_DIR = '/usr/local/bin'
 
 
-def run_experiment(project_name, target_name, args, output_path,
+def run_experiment(project_name, target_name, args, output_path, errlog_path,
                    build_output_path, upload_corpus_path, upload_coverage_path,
                    experiment_name, upload_reproducer_path):
   config = build_project.Config(testing=True,
@@ -72,6 +72,7 @@ def run_experiment(project_name, target_name, args, output_path,
 
   build = build_project.Build('libfuzzer', 'address', 'x86_64')
   local_output_path = '/workspace/output.log'
+  local_jcc_err_path = '/workspace/err.log'  # From jcc.go:360.
   local_corpus_path_base = '/workspace/corpus'
   local_corpus_path = os.path.join(local_corpus_path_base, target_name)
   default_target_path = os.path.join(build.out, target_name)
@@ -81,6 +82,24 @@ def run_experiment(project_name, target_name, args, output_path,
   local_stacktrace_path = os.path.join(build.out, 'stacktrace/')
   fuzzer_args = ' '.join(args + [f'-artifact_prefix={local_artifact_path}'])
 
+  # Upload JCC's err.log.
+  if errlog_path:
+    compile_step_index = -1
+    for i, step in enumerate(steps):
+      step_args = step.get('args', [])
+      if '&& compile' in ' '.join(step_args):
+        compile_step_index = i
+        break
+    if compile_step_index == -1:
+      print('Cannot find compile step.')
+    else:
+      # Insert the upload step right after compile step.
+      upload_jcc_err_step = {
+          'name': 'gcr.io/cloud-builders/gsutil',
+          'args': ['cp', local_jcc_err_path, errlog_path]
+      }
+      steps.insert(compile_step_index + 1, upload_jcc_err_step)
+
   env = build_project.get_env(project_yaml['language'], build)
   env.append('RUN_FUZZER_MODE=batch')
   env.append('CORPUS_DIR=' + local_corpus_path)
@@ -268,6 +287,10 @@ def main():
   parser.add_argument('--upload_build_log',
                       required=True,
                       help='GCS build log location.')
+  parser.add_argument('--upload_err_log',
+                      required=False,
+                      default='',
+                      help='GCS JCC error log location.')
   parser.add_argument('--upload_output_log',
                       required=True,
                       help='GCS log location.')
@@ -287,7 +310,7 @@ def main():
   args = parser.parse_args()
 
   run_experiment(args.project, args.target, args.args, args.upload_output_log,
-                 args.upload_build_log, args.upload_corpus,
+                 args.upload_err_log, args.upload_build_log, args.upload_corpus,
                  args.upload_coverage, args.experiment_name,
                  args.upload_reproducer)