rust: add module to convert between success/-errno and io::Result

It is a common convention in QEMU to return a positive value in case of
success, and a negated errno value in case of error.  Unfortunately,
using errno portably in Rust is a bit complicated; on Unix the errno
values are supported natively by io::Error, but on Windows they are not;
so, use the libc crate.

This is a set of utility functions that are used by both chardev and
block layer bindings.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/rust/qemu-api/meson.build b/rust/qemu-api/meson.build
index 2e9c1078b9..bcf1cf780f 100644
--- a/rust/qemu-api/meson.build
+++ b/rust/qemu-api/meson.build
@@ -2,6 +2,8 @@ _qemu_api_cfg = run_command(rustc_args,
   '--config-headers', config_host_h, '--features', files('Cargo.toml'),
   capture: true, check: true).stdout().strip().splitlines()
 
+libc_dep = dependency('libc-0.2-rs')
+
 # _qemu_api_cfg += ['--cfg', 'feature="allocator"']
 if rustc.version().version_compare('>=1.77.0')
   _qemu_api_cfg += ['--cfg', 'has_offset_of']
@@ -22,6 +24,7 @@ _qemu_api_rs = static_library(
       'src/cell.rs',
       'src/chardev.rs',
       'src/c_str.rs',
+      'src/errno.rs',
       'src/irq.rs',
       'src/memory.rs',
       'src/module.rs',
@@ -39,6 +42,7 @@ _qemu_api_rs = static_library(
   override_options: ['rust_std=2021', 'build.rust_std=2021'],
   rust_abi: 'rust',
   rust_args: _qemu_api_cfg,
+  dependencies: libc_dep,
 )
 
 rust.test('rust-qemu-api-tests', _qemu_api_rs,