util: Fix UB in SetStdinEcho when ENOTTY #34597

1. 
   maflcko commented at 11:37 am on February 16, 2026: member

   The call to tcgetattr may fail with ENOTTY, leaving the struct possibly uninitialized (UB).

   Fix this UB by returning early when isatty fails, or when tcgetattr fails. (Same for Windows)

   This can be tested by a command that fails valgrind before the change and passes after:

   0echo 'pipe' | valgrind --quiet ./bld-cmake/bin/bitcoin-cli -stdinrpcpass uptime
   

2. util: Fix UB in SetStdinEcho when ENOTTY fa5adfb13e
3. DrahtBot added the label Utils/log/libs on Feb 16, 2026
4. 
   DrahtBot commented at 11:37 am on February 16, 2026: contributor

   The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

   Reviews

   See the guideline for information on the review process.

   Type	Reviewers
   Concept ACK	l0rinc

   If your review is incorrectly listed, please copy-paste <!–meta-tag:bot-skip–> into the comment that the bot should ignore.

   Conflicts

   Reviewers, this pull request conflicts with the following ones:

   • #34004 (Implementation of SwiftSync by rustaceanrob)

   If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

5. 
   l0rinc commented at 12:46 pm on February 16, 2026: contributor

   concept ACK

   Does this enable the removal of https://github.com/bitcoin/bitcoin/blob/d7c9d6c2914aadd711544908d0fad8857a809c72/test/sanitizer_suppressions/ubsan#L58?

6. 
   maflcko commented at 1:08 pm on February 16, 2026: member

   No, that is just a harmless warning. I guess I can refactor it a bit while touching this…
7. refactor: Use static_cast<decltype(...)> to suppress integer sanitizer warning

   This refactor does not change any behavior, except for the integer
   sanitizer warning.
   
   Can be tested via:
   
   UBSAN_OPTIONS="suppressions=$(pwd)/test/sanitizer_suppressions/ubsan:print_stacktrace=1:halt_on_error=1:report_error_type=1" ./bld-cmake/bin/bitcoin-cli -stdinrpcpass uptime

   faff79629c
8. 
   maflcko commented at 1:53 pm on February 16, 2026: member

   Pushed that as well. Needs compilation with the integer sanitizer (-DSANITIZERS=integer, ref: https://godbolt.org/z/YGjWa89vs) and can be tested via:

   0UBSAN_OPTIONS="suppressions=$(pwd)/test/sanitizer_suppressions/ubsan:print_stacktrace=1:halt_on_error=1:report_error_type=1" ./bld-cmake/bin/bitcoin-cli -stdinrpcpass uptime
   

Contributors
maflcko DrahtBot l0rinc

Labels
Utils/log/libs