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TEST_MEOW_DIAGNOSTIC_IGNORED sparingly (#75317)
This is the last PR that's needed (for now) to get libc++'s tests
working with MSVC's STL.
The ADDITIONAL_COMPILE_FLAGS machinery is very useful, but also very
problematic for MSVC, as it doesn't understand most of Clang's compiler
options. We've been dealing with this by simply marking anything that
uses ADDITIONAL_COMPILE_FLAGS as FAIL or SKIPPED, but that creates
significant gaps in test coverage.
Fortunately, ADDITIONAL_COMPILE_FLAGS also supports "features", which
can be slightly enhanced to send Clang-compatible and MSVC-compatible
options to the right compilers.
This patch adds the gcc-style-warnings and cl-style-warnings Lit features,
and uses that to pass the appropriate warning flags to tests. It also uses
TEST_MEOW_DIAGNOSTIC_IGNORED for a few local suppressions of MSVC
warnings.
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This commit introduces basic annotations for `std::basic_string`,
mirroring the approach used in `std::vector` and `std::deque`.
Initially, only long strings with the default allocator will be
annotated. Short strings (_SSO - short string optimization_) and strings
with non-default allocators will be annotated in the near future, with
separate commits dedicated to enabling them. The process will be similar
to the workflow employed for enabling annotations in `std::deque`.
**Please note**: these annotations function effectively only when libc++
and libc++abi dylibs are instrumented (with ASan). This aligns with the
prevailing behavior of Memory Sanitizer.
To avoid breaking everything, this commit also appends
`_LIBCPP_INSTRUMENTED_WITH_ASAN` to `__config_site` whenever libc++ is
compiled with ASan. If this macro is not defined, string annotations are
not enabled. However, linking a binary that does **not** annotate
strings with a dynamic library that annotates strings, is not permitted.
Originally proposed here: https://reviews.llvm.org/D132769
Related patches on Phabricator:
- Turning on annotations for short strings:
https://reviews.llvm.org/D147680
- Turning on annotations for all allocators:
https://reviews.llvm.org/D146214
This PR is a part of a series of patches extending AddressSanitizer C++
container overflow detection capabilities by adding annotations, similar
to those existing in `std::vector` and `std::deque` collections. These
enhancements empower ASan to effectively detect instances where the
instrumented program attempts to access memory within a collection's
internal allocation that remains unused. This includes cases where
access occurs before or after the stored elements in `std::deque`, or
between the `std::basic_string`'s size (including the null terminator)
and capacity bounds.
The introduction of these annotations was spurred by a real-world
software bug discovered by Trail of Bits, involving an out-of-bounds
memory access during the comparison of two strings using the
`std::equals` function. This function was taking iterators
(`iter1_begin`, `iter1_end`, `iter2_begin`) to perform the comparison,
using a custom comparison function. When the `iter1` object exceeded the
length of `iter2`, an out-of-bounds read could occur on the `iter2`
object. Container sanitization, upon enabling these annotations, would
effectively identify and flag this potential vulnerability.
This Pull Request introduces basic annotations for `std::basic_string`.
Long strings exhibit structural similarities to `std::vector` and will
be annotated accordingly. Short strings are already implemented, but
will be turned on separately in a forthcoming commit. Look at [a
comment](https://github.com/llvm/llvm-project/pull/72677#issuecomment-1850554465)
below to read about SSO issues at current moment.
Due to the functionality introduced in
[D132522](https://github.com/llvm/llvm-project/commit/dd1b7b797a116eed588fd752fbe61d34deeb24e4),
the `__sanitizer_annotate_contiguous_container` function now offers
compatibility with all allocators. However, enabling this support will
be done in a subsequent commit. For the time being, only strings with
the default allocator will be annotated.
If you have any questions, please email:
- advenam.tacet@trailofbits.com
- disconnect3d@trailofbits.com
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