always use __errno_location for user ABI #614

yamt · 2025-08-12T07:41:32Z

upsides:

by avoiding direct accesses to the TLS, increase the chances for third-party libraries to provide a single binary for threaded and non-threaded wasi targets. see [1] for an example.

downsides:

increase the overhead of errno accesses. i suppose it isn't critical as errno is typically only accessed in the error handling logic. there are a few apis like strtoul which require errno accesses even in successful cases though.

upsides: * by avoiding direct accesses to the TLS, increase the chances for third-party libraries to provide a single binary for threaded and non-threaded wasi targets. see [1] for an example. downsides: * increase the overhead of errno accesses. i suppose it isn't critical as errno is typically only accessed in the error handling logic. there are a few apis like strtoul which require errno accesses even in successful cases though. [1] https://github.com/bytecodealliance/wasm-micro-runtime/blob/d95b0e3d46da8e88f484f236cb4222f5a6dc5926/core/iwasm/libraries/lib-socket/src/wasi/wasi_socket_ext.c#L15-L33

Provide feedback