[PATCH] D30684: [libFuzzer] Don't use same seed for all parallel jobs

[Vitaly Buka via Phabricator via llvm-commits]

vitalybuka created this revision.

If booth -seed and -jobs are set we could set deterministic but unique seed for
each jobs by combining input seed with a job number.


https://reviews.llvm.org/D30684

Files:
  lib/Fuzzer/FuzzerDriver.cpp
  lib/Fuzzer/test/fuzzer-jobs.test


Index: lib/Fuzzer/test/fuzzer-jobs.test
===================================================================
--- lib/Fuzzer/test/fuzzer-jobs.test
+++ lib/Fuzzer/test/fuzzer-jobs.test
@@ -8,7 +8,7 @@
 RUN: rm -f fuzz-{0,1}.log
 # Start fuzzer and in parallel check that the output files
 # that should be created exist.
-RUN: LLVMFuzzer-EmptyTest -max_total_time=4 -jobs=2 -workers=2 FuzzerJobsTestCORPUS > %t-fuzzer-jobs-test.log 2>&1 & export FUZZER_PID=$!
+RUN: LLVMFuzzer-EmptyTest -seed=127 -max_total_time=4 -jobs=2 -workers=2 FuzzerJobsTestCORPUS > %t-fuzzer-jobs-test.log 2>&1 & export FUZZER_PID=$!
 # Wait a short while to give time for the child processes
 # to start fuzzing
 RUN: sleep 2
@@ -27,5 +27,8 @@
 RUN: rm %t-fuzzer-jobs-test.log
 RUN: cd ../
 
+CHECK-DAG: Seed: 127
+CHECK-DAG: Seed: 128
+
 CHECK-DAG: Job 0 exited with exit code 0
 CHECK-DAG: Job 1 exited with exit code 0
Index: lib/Fuzzer/FuzzerDriver.cpp
===================================================================
--- lib/Fuzzer/FuzzerDriver.cpp
+++ lib/Fuzzer/FuzzerDriver.cpp
@@ -206,8 +206,11 @@
   while (true) {
     unsigned C = (*Counter)++;
     if (C >= NumJobs) break;
+    std::string Seed;
+    if (Flags.seed)
+      Seed = "-seed=" + std::to_string(C + Flags.seed);
     std::string Log = "fuzz-" + std::to_string(C) + ".log";
-    std::string ToRun = Cmd + " > " + Log + " 2>&1\n";
+    std::string ToRun = Cmd + " " + Seed + " > " + Log + " 2>&1\n";
     if (Flags.verbosity)
       Printf("%s", ToRun.c_str());
     int ExitCode = ExecuteCommand(ToRun);


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