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authorXiang Fan <sfanxiang@gmail.com>2019-06-06 08:39:20 +0800
committerXiang Fan <sfanxiang@gmail.com>2019-09-28 04:45:08 +0800
commitf71e0daa29b232d8f689f77fecb84dcb87fce6da (patch)
tree7e450a5f114b0973aad2b5b7799bc7f54c6776c7 /src/libstd/sys/unix/stack_overflow.rs
parenta37fe2de697bb1a9d304e4e811836e125f944cd5 (diff)
downloadrust-f71e0daa29b232d8f689f77fecb84dcb87fce6da.tar.gz
rust-f71e0daa29b232d8f689f77fecb84dcb87fce6da.zip
Add llvm.sideeffect to potential infinite loops and recursions
LLVM assumes that a thread will eventually cause side effect. This is
not true in Rust if a loop or recursion does nothing in its body,
causing undefined behavior even in common cases like `loop {}`.
Inserting llvm.sideeffect fixes the undefined behavior.

As a micro-optimization, only insert llvm.sideeffect when jumping back
in blocks or calling a function.

A patch for LLVM is expected to allow empty non-terminate code by
default and fix this issue from LLVM side.

https://github.com/rust-lang/rust/issues/28728
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