ffi/pointer_arithmetic_operators_test is failing on vm-asan-linux-release-x64

[derekxu16]

==365904==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 12 byte(s) in 1 object(s) allocated from:
    #0 0x5639d28de2cf in calloc ../llvm_build/tools/clang/stage2-bins/runtimes/runtimes-x86_64-unknown-linux-gnu-bins/compiler-rt/lib/asan/asan_malloc_linux.cpp:77:3
    #1 0x7f5df8486b5a  (<unknown module>)
    #2 0x7f5df68a3df1  (<unknown module>)
    #3 0x7f5df68a316c  (<unknown module>)
    #4 0x7f5df68a2ce9  (<unknown module>)
    #5 0x7f5df68a2c25  (<unknown module>)
    #6 0x7f5df68a2b52  (<unknown module>)
    #7 0x7f5df68a1a12  (<unknown module>)
    #8 0x7f5df68a1755  (<unknown module>)
    #9 0x7f5df68a080b  (<unknown module>)
    #10 0x7f5df8482ee5  (<unknown module>)
    #11 0x5639d2d314a7 in dart::DartEntry::InvokeFunction(dart::Function const&, dart::Array const&, dart::Array const&) /b/f/w/out/ReleaseASANX64/../../runtime/vm/dart_entry.cc:125:33
    #12 0x5639d2d35c0e in dart::DartEntry::InvokeFunction(dart::Function const&, dart::Array const&) /b/f/w/out/ReleaseASANX64/../../runtime/vm/dart_entry.cc:37:10
    #13 0x5639d2d35c0e in dart::DartLibraryCalls::HandleMessage(long, dart::Instance const&) /b/f/w/out/ReleaseASANX64/../../runtime/vm/dart_entry.cc:718:28
    #14 0x5639d2da549e in dart::IsolateMessageHandler::HandleMessage(std::__2::unique_ptr<dart::Message, std::__2::default_delete<dart::Message>>) /b/f/w/out/ReleaseASANX64/../../runtime/vm/isolate.cc:1394:15
    #15 0x5639d2e242df in dart::MessageHandler::HandleMessages(dart::MonitorLocker*, bool, bool) /b/f/w/out/ReleaseASANX64/../../runtime/vm/message_handler.cc:238:16
    #16 0x5639d2e2579e in dart::MessageHandler::TaskCallback() /b/f/w/out/ReleaseASANX64/../../runtime/vm/message_handler.cc:457:18
    #17 0x5639d31d6615 in dart::ThreadPool::WorkerLoop(dart::ThreadPool::Worker*) /b/f/w/out/ReleaseASANX64/../../runtime/vm/thread_pool.cc:158:15
    #18 0x5639d31d747a in dart::ThreadPool::Worker::Main(unsigned long) /b/f/w/out/ReleaseASANX64/../../runtime/vm/thread_pool.cc:330:9
    #19 0x5639d3013103 in dart::ThreadStart(void*) /b/f/w/out/ReleaseASANX64/../../runtime/vm/os_thread_linux.cc:154:5
    #20 0x5639d28dbc38 in asan_thread_start(void*) ../llvm_build/tools/clang/stage2-bins/runtimes/runtimes-x86_64-unknown-linux-gnu-bins/compiler-rt/lib/asan/asan_interceptors.cpp:234:28

SUMMARY: AddressSanitizer: 12 byte(s) leaked in 1 allocation(s).

--- Re-run this test:
python3 tools/test.py -n vm-asan-linux-release-x64 ffi/pointer_arithmetic_operators_test

https://ci.chromium.org/ui/p/dart/builders/ci.sandbox/vm-asan-linux-release-x64/335/overview

@dcharkes

[dcharkes]

@shikharish

void main() {
  Pointer<Int32> p = calloc<Int32>(3);
  p.value = 1;
  (p + 1).value = 2;
  (p + 2).value = 3;
  Expect.equals(1, p.value);
  p += 2;
  Expect.equals(3, p.value);
  p -= 1;
  Expect.equals(2, p.value);
  calloc.free(p); // <-- missing
}

[shikharish]

@shikharish

void main() {
  Pointer<Int32> p = calloc<Int32>(3);
  p.value = 1;
  (p + 1).value = 2;
  (p + 2).value = 3;
  Expect.equals(1, p.value);
  p += 2;
  Expect.equals(3, p.value);
  p -= 1;
  Expect.equals(2, p.value);
  calloc.free(p); // <-- missing
}

We cannot free a pointer after we have changed its address (by doing p+=2 and then p-=1). This code would give an error.

[dcharkes]

Ah, yes! We need to save the original p.

[shikharish]

Oh right. I didn't think of that while writing the test, my bad. I will upload a patch soon!

[dcharkes]

Thanks @shikharish !

You can add the following to the bottom of the commit message to ensure that the ASAN bots run before we land the patch:

Cq-Include-Trybots: luci.dart.try:vm-aot-asan-linux-release-x64-try,vm-asan-linux-release-x64-try

[shikharish]

Patch uploaded: https://dart-review.googlesource.com/c/sdk/+/342460