[PATCH v2 06/13] rust: modernize link_section usage for ELF platforms

[Paolo Bonzini <pbonzini@redhat.com>]

Some newer ABI implementations do not provide .ctors; and while
some linkers rewrite .ctors into .init_array, not all of them do.
Use the newer .init_array ABI, which works more reliably, and
apply it to all non-Apple, non-Windows platforms.

This is similar to how the ctor crate operates; without this change,
"#[derive(Object)]" does not work on Fedora 41.

Reviewed-by: Junjie Mao <junjie.mao@hotmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 rust/qemu-api-macros/src/lib.rs  |  7 +++++--
 rust/qemu-api/src/definitions.rs | 14 ++++++++++----
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/rust/qemu-api-macros/src/lib.rs b/rust/qemu-api-macros/src/lib.rs
index 59aba592d9a..70e3f920460 100644
--- a/rust/qemu-api-macros/src/lib.rs
+++ b/rust/qemu-api-macros/src/lib.rs
@@ -16,8 +16,11 @@ pub fn derive_object(input: TokenStream) -> TokenStream {
     let expanded = quote! {
         #[allow(non_upper_case_globals)]
         #[used]
-        #[cfg_attr(target_os = "linux", link_section = ".ctors")]
-        #[cfg_attr(target_os = "macos", link_section = "__DATA,__mod_init_func")]
+        #[cfg_attr(
+            not(any(target_vendor = "apple", target_os = "windows")),
+            link_section = ".init_array"
+        )]
+        #[cfg_attr(target_vendor = "apple", link_section = "__DATA,__mod_init_func")]
         #[cfg_attr(target_os = "windows", link_section = ".CRT$XCU")]
         pub static #module_static: extern "C" fn() = {
             extern "C" fn __register() {
diff --git a/rust/qemu-api/src/definitions.rs b/rust/qemu-api/src/definitions.rs
index 49ac59af123..3323a665d92 100644
--- a/rust/qemu-api/src/definitions.rs
+++ b/rust/qemu-api/src/definitions.rs
@@ -31,8 +31,11 @@ pub trait Class {
 macro_rules! module_init {
     ($func:expr, $type:expr) => {
         #[used]
-        #[cfg_attr(target_os = "linux", link_section = ".ctors")]
-        #[cfg_attr(target_os = "macos", link_section = "__DATA,__mod_init_func")]
+        #[cfg_attr(
+            not(any(target_vendor = "apple", target_os = "windows")),
+            link_section = ".init_array"
+        )]
+        #[cfg_attr(target_vendor = "apple", link_section = "__DATA,__mod_init_func")]
         #[cfg_attr(target_os = "windows", link_section = ".CRT$XCU")]
         pub static LOAD_MODULE: extern "C" fn() = {
             extern "C" fn __load() {
@@ -48,8 +51,11 @@ extern "C" fn __load() {
         // NOTE: To have custom identifiers for the ctor func we need to either supply
         // them directly as a macro argument or create them with a proc macro.
         #[used]
-        #[cfg_attr(target_os = "linux", link_section = ".ctors")]
-        #[cfg_attr(target_os = "macos", link_section = "__DATA,__mod_init_func")]
+        #[cfg_attr(
+            not(any(target_vendor = "apple", target_os = "windows")),
+            link_section = ".init_array"
+        )]
+        #[cfg_attr(target_vendor = "apple", link_section = "__DATA,__mod_init_func")]
         #[cfg_attr(target_os = "windows", link_section = ".CRT$XCU")]
         pub static LOAD_MODULE: extern "C" fn() = {
             extern "C" fn __load() {
-- 
2.46.2