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document our assumptions about symbols provided by the libc

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Ralf Jung 2023-08-03 14:05:18 +02:00
parent a922d1c0da
commit dfee1ba4c4
1 changed files with 9 additions and 5 deletions
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14
library/core/src/lib.rs
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@ -20,11 +20,15 @@
// FIXME: Fill me in with more detail when the interface settles
//! This library is built on the assumption of a few existing symbols:
//!
//! * `memcpy`, `memcmp`, `memset`, `strlen` - These are core memory routines which are
//! often generated by LLVM. Additionally, this library can make explicit
//! calls to these functions. Their signatures are the same as found in C.
//! 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).
//! * `memcpy`, `memmove`, `memset`, `memcmp`, `bcmp`, `strlen` - These are core memory routines
//! which are generated by Rust codegen backends. Additionally, this library can make explicit
//! calls to `strlen`. Their signatures are the same as found in C, but there are extra
//! 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.)
//! 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).
//!
//! * `rust_begin_panic` - This function takes four arguments, a
//! `fmt::Arguments`, a `&'static str`, and two `u32`'s. These four arguments