translate_c: handle forward declared variables

src/clang.zig

@@ -1050,6 +1050,12 @@ pub const VarDecl = opaque {
 
     pub const isStaticLocal = ZigClangVarDecl_isStaticLocal;
     extern fn ZigClangVarDecl_isStaticLocal(*const VarDecl) bool;
+
+    pub const isThisDeclarationADefinition = ZigClangVarDecl_isThisDeclarationADefinition;
+    extern fn ZigClangVarDecl_isThisDeclarationADefinition(*const VarDecl) bool;
+
+    pub const getDefinition = ZigClangVarDecl_getDefinition;
+    extern fn ZigClangVarDecl_getDefinition(*const VarDecl) ?*const VarDecl;
 };
 
 pub const VectorType = opaque {

src/translate_c.zig

@@ -572,6 +572,12 @@ fn visitVarDecl(c: *Context, var_decl: *const clang.VarDecl, mangled_name: ?[]co
     if (c.global_scope.sym_table.contains(var_name))
         return; // Avoid processing this decl twice
 
+    // Skip this declaration if a proper definition exists
+    if (!var_decl.isThisDeclarationADefinition()) {
+        if (var_decl.getDefinition()) |def|
+            return visitVarDecl(c, def, mangled_name);
+    }
+
     const is_pub = mangled_name == null;
     const is_threadlocal = var_decl.getTLSKind() != .None;
     const scope = &c.global_scope.base;

src/zig_clang.cpp

@@ -3310,6 +3310,16 @@ bool ZigClangVarDecl_isStaticLocal(const struct ZigClangVarDecl *self) {
     return casted->isStaticLocal();
 }
 
+bool ZigClangVarDecl_isThisDeclarationADefinition(const struct ZigClangVarDecl *self) {
+    auto casted = reinterpret_cast<const clang::VarDecl *>(self);
+    return casted->isThisDeclarationADefinition();
+}
+
+const ZigClangVarDecl *ZigClangVarDecl_getDefinition(const struct ZigClangVarDecl *self) {
+    auto casted = reinterpret_cast<const clang::VarDecl *>(self);
+    return reinterpret_cast<const ZigClangVarDecl *>(casted->getDefinition());
+}
+
 enum ZigClangBuiltinTypeKind ZigClangBuiltinType_getKind(const struct ZigClangBuiltinType *self) {
     auto casted = reinterpret_cast<const clang::BuiltinType *>(self);
     return (ZigClangBuiltinTypeKind)casted->getKind();

src/zig_clang.h

@@ -1493,6 +1493,8 @@ ZIG_EXTERN_C const struct ZigClangAPValue *ZigClangVarDecl_evaluateValue(const s
 ZIG_EXTERN_C struct ZigClangQualType ZigClangVarDecl_getTypeSourceInfo_getType(const struct ZigClangVarDecl *);
 ZIG_EXTERN_C enum ZigClangStorageClass ZigClangVarDecl_getStorageClass(const struct ZigClangVarDecl *self);
 ZIG_EXTERN_C bool ZigClangVarDecl_isStaticLocal(const struct ZigClangVarDecl *self);
+ZIG_EXTERN_C bool ZigClangVarDecl_isThisDeclarationADefinition(const struct ZigClangVarDecl *);
+ZIG_EXTERN_C const ZigClangVarDecl *ZigClangVarDecl_getDefinition(const struct ZigClangVarDecl *);
 
 ZIG_EXTERN_C bool ZigClangSourceLocation_eq(struct ZigClangSourceLocation a, struct ZigClangSourceLocation b);