From 007ac778e1856fb819540b57d84595132b8d1c84 Mon Sep 17 00:00:00 2001
From: Francisco Gouveia <francisco.t.gouveia@tecnico.ulisboa.pt>
Date: Wed, 19 Aug 2026 11:11:57 +0100
Subject: [PATCH 1/2] Add a new `IsConvertableGlobalVarDecl` function to avoid
 empty `thread_local`s

---
 cpp2rust/converter/converter.cpp                | 17 +++++++++++++----
 cpp2rust/converter/converter.h                  |  2 ++
 .../converter/models/converter_refcount.cpp     |  3 +++
 3 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/cpp2rust/converter/converter.cpp b/cpp2rust/converter/converter.cpp
index 59410ced..fbab6edc 100644
--- a/cpp2rust/converter/converter.cpp
+++ b/cpp2rust/converter/converter.cpp
@@ -457,6 +457,17 @@ void Converter::ConvertVaListVarDecl(clang::VarDecl *decl) {
   StrCat(keyword_mut_, GetNamedDeclAsString(decl), token::kColon, "VaList");
 }
 
+bool Converter::IsConvertableGlobalVarDecl(clang::VarDecl *decl) {
+  if (!decl->isFileVarDecl()) {
+    return true;
+  }
+  if (decl->isThisDeclarationADefinition() == clang::VarDecl::DeclarationOnly &&
+      !decl->hasInit()) {
+    return false;
+  }
+  return !globals_.contains(GetNamedDeclAsString(decl));
+}
+
 bool Converter::ConvertVarDeclSkipInit(clang::VarDecl *decl) {
   auto qual_type = decl->getType();
   auto name = GetNamedDeclAsString(decl);
@@ -467,12 +478,10 @@ bool Converter::ConvertVarDeclSkipInit(clang::VarDecl *decl) {
   }
 
   if (decl->isFileVarDecl()) {
-    if ((decl->isThisDeclarationADefinition() ==
-             clang::VarDecl::DeclarationOnly &&
-         !decl->hasInit()) ||
-        !globals_.insert(name).second) {
+    if (!IsConvertableGlobalVarDecl(decl)) {
       return false;
     }
+    globals_.insert(name);
     StrCat(AccessSpecifierAsString(decl->getAccess()), keyword::kStatic,
            keyword_mut_);
     ENSURE(decl_ids_.insert(GetID(decl)).second);
diff --git a/cpp2rust/converter/converter.h b/cpp2rust/converter/converter.h
index 8a55ef2b..285bb600 100644
--- a/cpp2rust/converter/converter.h
+++ b/cpp2rust/converter/converter.h
@@ -100,6 +100,8 @@ class Converter : public clang::RecursiveASTVisitor<Converter> {
 
   virtual void ConvertGlobalVarDecl(clang::VarDecl *decl);
 
+  bool IsConvertableGlobalVarDecl(clang::VarDecl *decl);
+
   virtual void ConvertVaListVarDecl(clang::VarDecl *decl);
 
   virtual bool ConvertVarDeclSkipInit(clang::VarDecl *decl);
diff --git a/cpp2rust/converter/models/converter_refcount.cpp b/cpp2rust/converter/models/converter_refcount.cpp
index d0580d94..a4441a1e 100644
--- a/cpp2rust/converter/models/converter_refcount.cpp
+++ b/cpp2rust/converter/models/converter_refcount.cpp
@@ -740,6 +740,9 @@ void ConverterRefCount::EmitHoistedInArmAssignment(clang::VarDecl *decl) {
 }
 
 void ConverterRefCount::ConvertGlobalVarDecl(clang::VarDecl *decl) {
+  if (!IsConvertableGlobalVarDecl(decl)) {
+    return;
+  }
   StrCat("thread_local!");
   {
     PushParen paren(*this);

From 221ee449d09b28e7d2e43b002d79bffb56c20064 Mon Sep 17 00:00:00 2001
From: Francisco Gouveia <francisco.t.gouveia@tecnico.ulisboa.pt>
Date: Wed, 19 Aug 2026 11:25:18 +0100
Subject: [PATCH 2/2] Add a test to ensure no empty `thread_local`s are being
 generated

---
 tests/unit/extern_global.c               |  4 ++++
 tests/unit/out/refcount/extern_global.rs | 17 +++++++++++++++++
 tests/unit/out/unsafe/extern_global.rs   | 17 +++++++++++++++++
 3 files changed, 38 insertions(+)
 create mode 100644 tests/unit/extern_global.c
 create mode 100644 tests/unit/out/refcount/extern_global.rs
 create mode 100644 tests/unit/out/unsafe/extern_global.rs

diff --git a/tests/unit/extern_global.c b/tests/unit/extern_global.c
new file mode 100644
index 00000000..4d8fcc5a
--- /dev/null
+++ b/tests/unit/extern_global.c
@@ -0,0 +1,4 @@
+extern int x;
+int x;
+
+int main(void) { return x; }
diff --git a/tests/unit/out/refcount/extern_global.rs b/tests/unit/out/refcount/extern_global.rs
new file mode 100644
index 00000000..3b1cab0e
--- /dev/null
+++ b/tests/unit/out/refcount/extern_global.rs
@@ -0,0 +1,17 @@
+extern crate libcc2rs;
+use libcc2rs::*;
+use std::cell::RefCell;
+use std::collections::BTreeMap;
+use std::io::prelude::*;
+use std::io::{Read, Seek, Write};
+use std::os::fd::AsFd;
+use std::rc::{Rc, Weak};
+thread_local!(
+    pub static x_0: Value<i32> = <Value<i32>>::default();
+);
+pub fn main() {
+    std::process::exit(main_0());
+}
+fn main_0() -> i32 {
+    return (*x_0.with(Value::clone).borrow());
+}
diff --git a/tests/unit/out/unsafe/extern_global.rs b/tests/unit/out/unsafe/extern_global.rs
new file mode 100644
index 00000000..1b531f71
--- /dev/null
+++ b/tests/unit/out/unsafe/extern_global.rs
@@ -0,0 +1,17 @@
+extern crate libc;
+use libc::*;
+extern crate libcc2rs;
+use libcc2rs::*;
+use std::collections::BTreeMap;
+use std::io::{Read, Seek, Write};
+use std::os::fd::{AsFd, FromRawFd, IntoRawFd};
+use std::rc::Rc;
+pub static mut x_0: i32 = unsafe { 0_i32 };
+pub fn main() {
+    unsafe {
+        std::process::exit(main_0() as i32);
+    }
+}
+unsafe fn main_0() -> i32 {
+    return x_0;
+}