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Rollup merge of #117312 - RalfJung:memcpy-assumptions, r=Mark-Simulacrum

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memcpy assumptions: link to source showing that GCC makes the same assumption

I finally stumbled upon a source showing that GCC also generates overlapping `memcpy`. So if we're linking major C compilers making such assumptions here, let's have both clang and GCC.
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Guillaume Gomez 2023-10-29 12:35:01 +01:00 committed by GitHub
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library/core/src/lib.rs
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@ -26,7 +26,8 @@
//! assumptions about their semantics: For `memcpy`, `memmove`, `memset`, `memcmp`, and `bcmp`, if
//! the `n` parameter is 0, the function is assumed to not be UB. Furthermore, for `memcpy`, if
//! source and target pointer are equal, the function is assumed to not be UB.
//! (Note that these are [standard assumptions](https://reviews.llvm.org/D86993) among compilers.)
//! (Note that these are standard assumptions among compilers:
//! [clang](https://reviews.llvm.org/D86993) and [GCC](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=32667) do the same.)
//! These functions are often provided by the system libc, but can also be provided by the
//! [compiler-builtins crate](https://crates.io/crates/compiler_builtins).
//! Note that the library does not guarantee that it will always make these assumptions, so Rust