Undefined behavior in AutoFile::write (gcc only) #28761

1. 
   dergoegge commented at 1:03 pm on October 31, 2023: member

    0$ CC=gcc CXX=g++ ./configure --with-sanitizers=undefined && make
    1$ export UBSAN_OPTIONS=print_stacktrace=1:halt_on_error=1:report_error_type=1
    2$ FUZZ=utxo_snapshot ./src/test/fuzz/fuzz ../qa-assets/fuzz_seed_corpus/utxo_snapshot/
    3streams.cpp:48:24: runtime error: null pointer passed as argument 1, which is declared to never be null
    4    [#0](/bitcoin-bitcoin/0/) 0x5634737bcdc0 in AutoFile::write(Span<std::byte const>) src/streams.cpp:48
    5    [#1](/bitcoin-bitcoin/1/) 0x5634749e553b in void Serialize<AutoFile, unsigned char const>(AutoFile&, Span<unsigned char const>) serialize.h:288
    6    [#2](/bitcoin-bitcoin/2/) 0x5634749e553b in AutoFile& AutoFile::operator<< <Span<unsigned char const> >(Span<unsigned char const> const&) streams.h:527
    7    [#3](/bitcoin-bitcoin/3/) 0x5634749e553b in utxo_snapshot_fuzz_target test/fuzz/utxo_snapshot.cpp:45
    8    ...
    9$ ./src/test/test_bitcoin --run_test="net_tests"
   10streams.cpp:49:24: runtime error: null pointer passed as argument 1, which is declared to never be null
   11    [#0](/bitcoin-bitcoin/0/) 0x55613837a3ee in AutoFile::write(Span<std::byte const>) src/streams.cpp:49
   12    [#1](/bitcoin-bitcoin/1/) 0x55613b9747cc in void Serialize<AutoFile, unsigned char const>(AutoFile&, Span<unsigned char const>) serialize.h:288
   13    [#2](/bitcoin-bitcoin/2/) 0x55613b9747cc in AutoFile& AutoFile::operator<< <Span<unsigned char const> >(Span<unsigned char const> const&) streams.h:527
   14    [#3](/bitcoin-bitcoin/3/) 0x55613b9747cc in CaptureMessageToFile src/net.cpp:3885
   

   This is harmless since the spans passed to AutoFile::write will always be of size 0 in this case.

2. 
   maflcko commented at 4:49 pm on October 31, 2023: member

   I think this is a “bug” in gcc that should be fixed upstream. See also the related discussion in https://reviews.llvm.org/D86993
3. maflcko added the label Upstream on Oct 31, 2023
4. maflcko added the label Tests on Oct 31, 2023
5. 
   maflcko commented at 3:47 pm on November 2, 2023: member

   Also, a suppression can be added in the meantime, if anyone is using g++
6. willcl-ark closed this on Oct 14, 2024

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