[clang] [clang][bytecode] Reject uninitialized bases in builtin_bit_cast (PR #194625)

Thu Apr 30 02:34:22 PDT 2026

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `sanitizer-x86_64-linux` running on `sanitizer-buildbot2` while building `clang` at step 2 "annotate".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/66/builds/30201

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 2 (annotate) failure: 'python ../sanitizer_buildbot/sanitizers/zorg/buildbot/builders/sanitizers/buildbot_selector.py' (failure)
...
[415/421] Generating MSAN_INST_GTEST.gtest-all.cc.x86_64-with-call.o
[416/421] Generating MSAN_INST_GTEST.gtest-all.cc.x86_64.o
[417/421] Generating MSAN_INST_TEST_OBJECTS.msan_test.cpp.x86_64-with-call.o
[418/421] Generating Msan-x86_64-with-call-Test
[419/421] Generating MSAN_INST_TEST_OBJECTS.msan_test.cpp.x86_64.o
[420/421] Generating Msan-x86_64-Test
[420/421] Running compiler_rt regression tests
llvm-lit: /home/b/sanitizer-x86_64-linux/build/llvm-project/llvm/utils/lit/lit/main.py:74: note: The test suite configuration requested an individual test timeout of 0 seconds but a timeout of 900 seconds was requested on the command line. Forcing timeout to be 900 seconds.
-- Testing: 5426 of 11498 tests, 64 workers --
Testing:  0.. 10.. 20.. 30.. 40.. 50
FAIL: SanitizerCommon-tsan-x86_64-Linux :: Posix/create_thread_loop2.cpp (2982 of 5426)
******************** TEST 'SanitizerCommon-tsan-x86_64-Linux :: Posix/create_thread_loop2.cpp' FAILED ********************
Exit Code: 66

Command Output (stdout):
--
# RUN: at line 3
/home/b/sanitizer-x86_64-linux/build/build_default/./bin/clang  --driver-mode=g++ -gline-tables-only -fsanitize=thread  -m64 -funwind-tables  -I/home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test -ldl -O3 -pthread /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/sanitizer_common/TestCases/Posix/create_thread_loop2.cpp -o /home/b/sanitizer-x86_64-linux/build/build_default/runtimes/runtimes-bins/compiler-rt/test/sanitizer_common/tsan-x86_64-Linux/Posix/Output/create_thread_loop2.cpp.tmp &&  /home/b/sanitizer-x86_64-linux/build/build_default/runtimes/runtimes-bins/compiler-rt/test/sanitizer_common/tsan-x86_64-Linux/Posix/Output/create_thread_loop2.cpp.tmp 10
# executed command: /home/b/sanitizer-x86_64-linux/build/build_default/./bin/clang --driver-mode=g++ -gline-tables-only -fsanitize=thread -m64 -funwind-tables -I/home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test -ldl -O3 -pthread /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/sanitizer_common/TestCases/Posix/create_thread_loop2.cpp -o /home/b/sanitizer-x86_64-linux/build/build_default/runtimes/runtimes-bins/compiler-rt/test/sanitizer_common/tsan-x86_64-Linux/Posix/Output/create_thread_loop2.cpp.tmp
# note: command had no output on stdout or stderr
# executed command: /home/b/sanitizer-x86_64-linux/build/build_default/runtimes/runtimes-bins/compiler-rt/test/sanitizer_common/tsan-x86_64-Linux/Posix/Output/create_thread_loop2.cpp.tmp 10
# .---command stderr------------
# | ThreadSanitizer: CHECK failed: tsan_platform.h:992 "((IsAppMemImpl::Apply<Mapping>(x))) != (0)" (0x0, 0x0) (tid=3556570)
# |     #0 __tsan::CheckUnwind() /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp:697:21 (create_thread_loop2.cpp.tmp+0x10048f)
# |     #1 __sanitizer::CheckFailed(char const*, int, char const*, unsigned long long, unsigned long long) /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/sanitizer_common/sanitizer_termination.cpp:86:5 (create_thread_loop2.cpp.tmp+0x8b782)
# |     #2 unsigned long __tsan::MemToShadowImpl::Apply<__tsan::Mapping48AddressSpace>(unsigned long) /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/tsan/rtl/tsan_platform.h:992:5 (create_thread_loop2.cpp.tmp+0xffeeb)
# |     #3 auto __tsan::SelectMapping<__tsan::MemToShadowImpl, unsigned long>(unsigned long) /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/tsan/rtl/tsan_platform.h:800:10 (create_thread_loop2.cpp.tmp+0xffeeb)
# |     #4 __tsan::MemToShadow(unsigned long) /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/tsan/rtl/tsan_platform.h:1003:7 (create_thread_loop2.cpp.tmp+0xffeeb)
# |     #5 __tsan::DontNeedShadowFor(unsigned long, unsigned long) /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp (create_thread_loop2.cpp.tmp+0xffeeb)
# |     #6 __tsan::ThreadFinish(__tsan::ThreadState*) /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/tsan/rtl/tsan_rtl_thread.cpp:244:5 (create_thread_loop2.cpp.tmp+0x11efc8)
# |     #7 __tsan::DestroyThreadState() /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp:1004:3 (create_thread_loop2.cpp.tmp+0xe0921)
# |     #8 thread_finalize(void*) /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp:1033:3 (create_thread_loop2.cpp.tmp+0xe0921)
# |     #9 <null> <null> (libc.so.6+0xa9071) (BuildId: ae327f26c123ea1374623c41e676a4bf00e5c1cb)
# |     #10 <null> <null> (libc.so.6+0xabfa0) (BuildId: ae327f26c123ea1374623c41e676a4bf00e5c1cb)
# |     #11 <null> <null> (libc.so.6+0x13f67b) (BuildId: ae327f26c123ea1374623c41e676a4bf00e5c1cb)
# | 
# `-----------------------------
# error: command failed with exit status: 66

--

********************
Testing:  0.. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90.. 
Slowest Tests:
--------------------------------------------------------------------------
68.96s: ThreadSanitizer-x86_64 :: deadlock_detector_stress_test.cpp
54.75s: ThreadSanitizer-x86_64 :: restore_stack.cpp
41.36s: libFuzzer-i386-static-libcxx-Linux :: fork_corpus_groups.test
40.16s: libFuzzer-i386-default-Linux :: fork_corpus_groups.test
Step 11 (test compiler-rt debug) failure: test compiler-rt debug (failure)
...
[415/421] Generating MSAN_INST_GTEST.gtest-all.cc.x86_64-with-call.o
[416/421] Generating MSAN_INST_GTEST.gtest-all.cc.x86_64.o
[417/421] Generating MSAN_INST_TEST_OBJECTS.msan_test.cpp.x86_64-with-call.o
[418/421] Generating Msan-x86_64-with-call-Test
[419/421] Generating MSAN_INST_TEST_OBJECTS.msan_test.cpp.x86_64.o
[420/421] Generating Msan-x86_64-Test
[420/421] Running compiler_rt regression tests
llvm-lit: /home/b/sanitizer-x86_64-linux/build/llvm-project/llvm/utils/lit/lit/main.py:74: note: The test suite configuration requested an individual test timeout of 0 seconds but a timeout of 900 seconds was requested on the command line. Forcing timeout to be 900 seconds.
-- Testing: 5426 of 11498 tests, 64 workers --
Testing:  0.. 10.. 20.. 30.. 40.. 50
FAIL: SanitizerCommon-tsan-x86_64-Linux :: Posix/create_thread_loop2.cpp (2982 of 5426)
******************** TEST 'SanitizerCommon-tsan-x86_64-Linux :: Posix/create_thread_loop2.cpp' FAILED ********************
Exit Code: 66

Command Output (stdout):
--
# RUN: at line 3
/home/b/sanitizer-x86_64-linux/build/build_default/./bin/clang  --driver-mode=g++ -gline-tables-only -fsanitize=thread  -m64 -funwind-tables  -I/home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test -ldl -O3 -pthread /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/sanitizer_common/TestCases/Posix/create_thread_loop2.cpp -o /home/b/sanitizer-x86_64-linux/build/build_default/runtimes/runtimes-bins/compiler-rt/test/sanitizer_common/tsan-x86_64-Linux/Posix/Output/create_thread_loop2.cpp.tmp &&  /home/b/sanitizer-x86_64-linux/build/build_default/runtimes/runtimes-bins/compiler-rt/test/sanitizer_common/tsan-x86_64-Linux/Posix/Output/create_thread_loop2.cpp.tmp 10
# executed command: /home/b/sanitizer-x86_64-linux/build/build_default/./bin/clang --driver-mode=g++ -gline-tables-only -fsanitize=thread -m64 -funwind-tables -I/home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test -ldl -O3 -pthread /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/test/sanitizer_common/TestCases/Posix/create_thread_loop2.cpp -o /home/b/sanitizer-x86_64-linux/build/build_default/runtimes/runtimes-bins/compiler-rt/test/sanitizer_common/tsan-x86_64-Linux/Posix/Output/create_thread_loop2.cpp.tmp
# note: command had no output on stdout or stderr
# executed command: /home/b/sanitizer-x86_64-linux/build/build_default/runtimes/runtimes-bins/compiler-rt/test/sanitizer_common/tsan-x86_64-Linux/Posix/Output/create_thread_loop2.cpp.tmp 10
# .---command stderr------------
# | ThreadSanitizer: CHECK failed: tsan_platform.h:992 "((IsAppMemImpl::Apply<Mapping>(x))) != (0)" (0x0, 0x0) (tid=3556570)
# |     #0 __tsan::CheckUnwind() /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp:697:21 (create_thread_loop2.cpp.tmp+0x10048f)
# |     #1 __sanitizer::CheckFailed(char const*, int, char const*, unsigned long long, unsigned long long) /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/sanitizer_common/sanitizer_termination.cpp:86:5 (create_thread_loop2.cpp.tmp+0x8b782)
# |     #2 unsigned long __tsan::MemToShadowImpl::Apply<__tsan::Mapping48AddressSpace>(unsigned long) /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/tsan/rtl/tsan_platform.h:992:5 (create_thread_loop2.cpp.tmp+0xffeeb)
# |     #3 auto __tsan::SelectMapping<__tsan::MemToShadowImpl, unsigned long>(unsigned long) /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/tsan/rtl/tsan_platform.h:800:10 (create_thread_loop2.cpp.tmp+0xffeeb)
# |     #4 __tsan::MemToShadow(unsigned long) /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/tsan/rtl/tsan_platform.h:1003:7 (create_thread_loop2.cpp.tmp+0xffeeb)
# |     #5 __tsan::DontNeedShadowFor(unsigned long, unsigned long) /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp (create_thread_loop2.cpp.tmp+0xffeeb)
# |     #6 __tsan::ThreadFinish(__tsan::ThreadState*) /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/tsan/rtl/tsan_rtl_thread.cpp:244:5 (create_thread_loop2.cpp.tmp+0x11efc8)
# |     #7 __tsan::DestroyThreadState() /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp:1004:3 (create_thread_loop2.cpp.tmp+0xe0921)
# |     #8 thread_finalize(void*) /home/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp:1033:3 (create_thread_loop2.cpp.tmp+0xe0921)
# |     #9 <null> <null> (libc.so.6+0xa9071) (BuildId: ae327f26c123ea1374623c41e676a4bf00e5c1cb)
# |     #10 <null> <null> (libc.so.6+0xabfa0) (BuildId: ae327f26c123ea1374623c41e676a4bf00e5c1cb)
# |     #11 <null> <null> (libc.so.6+0x13f67b) (BuildId: ae327f26c123ea1374623c41e676a4bf00e5c1cb)
# | 
# `-----------------------------
# error: command failed with exit status: 66

--

********************
Testing:  0.. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90.. 
Slowest Tests:
--------------------------------------------------------------------------
68.96s: ThreadSanitizer-x86_64 :: deadlock_detector_stress_test.cpp
54.75s: ThreadSanitizer-x86_64 :: restore_stack.cpp
41.36s: libFuzzer-i386-static-libcxx-Linux :: fork_corpus_groups.test
40.16s: libFuzzer-i386-default-Linux :: fork_corpus_groups.test

```

</details>

https://github.com/llvm/llvm-project/pull/194625