This section informs you about known "gotchas". Keep in mind, that this section is (and always will be) incomplete. For suggestions and amendments, feel free to contribute to this guide.
Most target-feature problems arise, when mixing code that have the target-feature enabled with code that have it disabled. If you want to avoid undefined behavior, it is recommended to build all code (including the standard library and imported crates) with a common set of target-features.
By default, compiling your code with the -C target-feature flag will not recompile the entire standard library and/or imported crates with matching target features. Therefore, target features are generally considered as unsafe. Using #[target_feature] on individual functions makes the function unsafe.
Examples:
| Target-Feature | Issue | Seen on | Description | Details |
|---|---|---|---|---|
+soft-float and -sse |
Segfaults and ABI mismatches | x86 and x86-64 |
The x86 and x86_64 architecture uses SSE registers (aka xmm) for floating point operations. Using software emulated floats ("soft-floats") disables usage of xmm registers, but parts of Rust's core libraries (e.g. std::f32 or std::f64) are compiled without soft-floats and expect parameters to be passed in xmm registers. This leads to ABI mismatches. Attempting to compile with disabled SSE causes the same error, too. |
#63466 |