Fix i686 MSVC linking by handling name mangling

cargo-auditable/src/object_file.rs

@@ -322,6 +322,28 @@ windows
         assert_eq!(result.architecture(), Architecture::X86_64);
     }
 
+    #[test]
+    fn test_create_object_file_windows_msvc_i686() {
+        let rustc_output = br#"debug_assertions
+target_arch="x86"
+target_endian="little"
+target_env="msvc"
+target_family="windows"
+target_feature="fxsr"
+target_feature="sse"
+target_feature="sse2"
+target_os="windows"
+target_pointer_width="32"
+target_vendor="pc"
+windows
+"#;
+        let target_triple = "i686-pc-windows-msvc";
+        let target_info = parse_rustc_target_info(rustc_output);
+        let result = create_object_file(&target_info, target_triple).unwrap();
+        assert_eq!(result.format(), BinaryFormat::Coff);
+        assert_eq!(result.architecture(), Architecture::I386);
+    }
+
     #[test]
     fn test_create_object_file_windows_gnu() {
         let rustc_output = br#"debug_assertions

cargo-auditable/src/platform_detection.rs

@@ -22,6 +22,10 @@ pub fn is_32bit(target_info: &RustcTargetInfo) -> bool {
     key_equals(target_info, "target_pointer_width", "32")
 }
 
+pub fn is_32bit_x86(target_info: &RustcTargetInfo) -> bool {
+    key_equals(target_info, "target_arch", "x86")
+}
+
 fn key_equals(target_info: &RustcTargetInfo, key: &str, value: &str) -> bool {
     target_info.get(key).map(|s| s.as_str()) == Some(value)
 }

cargo-auditable/src/rustc_wrapper.rs

@@ -6,7 +6,7 @@ use std::{
 
 use crate::{
     binary_file, collect_audit_data,
-    platform_detection::{is_apple, is_msvc, is_wasm},
+    platform_detection::{is_32bit_x86, is_apple, is_msvc, is_wasm},
     rustc_arguments::{self, should_embed_audit_data},
     target_info,
 };
@@ -134,7 +134,14 @@ fn rustc_command_with_audit_data(rustc_path: &OsStr) -> Option<Command> {
                 command.arg("-Clink-arg=-Wl,-u,_AUDITABLE_VERSION_INFO");
             }
         } else if is_msvc(&target_info) {
-            command.arg("-Clink-arg=/INCLUDE:AUDITABLE_VERSION_INFO");
+            // On x86 MSVC, the `object` crate's CoffI386 mangling adds a `_`
+            // prefix to global symbols, so the linker must reference the
+            // decorated name.
+            if is_32bit_x86(&target_info) {
+                command.arg("-Clink-arg=/INCLUDE:_AUDITABLE_VERSION_INFO");
+            } else {
+                command.arg("-Clink-arg=/INCLUDE:AUDITABLE_VERSION_INFO");
+            }
         } else if is_wasm(&target_info) {
             // We don't emit the symbol name in WASM, so nothing to do
         } else {