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| author | Marco Elver <elver@google.com> | 2022-01-12 14:40:41 +0100 |
|---|---|---|
| committer | Marco Elver <elver@google.com> | 2022-01-12 15:13:10 +0100 |
| commit | 732ad8ea62edc403727af57537b5d83dcfa937aa (patch) | |
| tree | 3eeefb8b126db36d88f37b4d52e29b42c876e84c /llvm/tools/llvm-readobj/llvm-readobj.cpp | |
| parent | c8c3021e9fe6de5dd45e8893636399e50f3d11f7 (diff) | |
| download | llvm-732ad8ea62edc403727af57537b5d83dcfa937aa.zip llvm-732ad8ea62edc403727af57537b5d83dcfa937aa.tar.gz llvm-732ad8ea62edc403727af57537b5d83dcfa937aa.tar.bz2 | |
[clang][auto-init] Provide __builtin_alloca*_uninitialized variants
When `-ftrivial-auto-var-init=` is enabled, allocas unconditionally
receive auto-initialization since [1].
In certain cases, it turns out, this is causing problems. For example,
when using alloca to add a random stack offset, as the Linux kernel does
on syscall entry [2]. In this case, none of the alloca'd stack memory is
ever used, and initializing it should be controllable; furthermore, it
is not always possible to safely call memset (see [2]).
Introduce `__builtin_alloca_uninitialized()` (and
`__builtin_alloca_with_align_uninitialized`), which never performs
initialization when `-ftrivial-auto-var-init=` is enabled.
[1] https://reviews.llvm.org/D60548
[2] https://lkml.kernel.org/r/YbHTKUjEejZCLyhX@elver.google.com
Reviewed By: glider
Differential Revision: https://reviews.llvm.org/D115440
Diffstat (limited to 'llvm/tools/llvm-readobj/llvm-readobj.cpp')
0 files changed, 0 insertions, 0 deletions