cbe: don't emit extern decls that are already exported

2 files changed, 27 insertions, 12 deletions

diff --git a/src/codegen/c.zig b/src/codegen/c.zig
index ef125c6aee..48719d6efe 100644
--- a/src/codegen/c.zig
+++ b/src/codegen/c.zig
@@ -2427,11 +2427,15 @@ pub fn genFunc(f: *Function) !void {
     defer tracy.end();
 
     const o = &f.object;
+    const tv: TypedValue = .{
+        .ty = o.dg.decl.ty,
+        .val = o.dg.decl.val,
+    };
 
     o.code_header = std.ArrayList(u8).init(f.object.dg.gpa);
     defer o.code_header.deinit();
 
-    const is_global = o.dg.module.decl_exports.contains(f.func.owner_decl);
+    const is_global = o.dg.declIsGlobal(tv);
     const fwd_decl_writer = o.dg.fwd_decl.writer();
     try fwd_decl_writer.writeAll(if (is_global) "zig_extern " else "static ");
     try o.dg.renderFunctionSignature(fwd_decl_writer, .Forward);
@@ -2478,14 +2482,11 @@ pub fn genDecl(o: *Object) !void {
         try fwd_decl_writer.writeAll(";\n");
     } else if (tv.val.castTag(.variable)) |var_payload| {
         const variable: *Module.Var = var_payload.data;
+
         const is_global = o.dg.declIsGlobal(tv) or variable.is_extern;
         const fwd_decl_writer = o.dg.fwd_decl.writer();
 
-        const decl_c_value: CValue = if (is_global) .{
-            .bytes = mem.span(o.dg.decl.name),
-        } else .{
-            .decl = o.dg.decl_index,
-        };
+        const decl_c_value = CValue{ .decl = o.dg.decl_index };
 
         try fwd_decl_writer.writeAll(if (is_global) "zig_extern " else "static ");
         if (variable.is_threadlocal) try fwd_decl_writer.writeAll("zig_threadlocal ");
diff --git a/src/link/C.zig b/src/link/C.zig
index 4af69e6fcf..a2d7ee143c 100644
--- a/src/link/C.zig
+++ b/src/link/C.zig
@@ -290,9 +290,17 @@ pub fn flushModule(self: *C, comp: *Compilation, prog_node: *std.Progress.Node)
         f.remaining_decls.putAssumeCapacityNoClobber(decl_index, {});
     }
 
-    while (f.remaining_decls.popOrNull()) |kv| {
-        const decl_index = kv.key;
-        try self.flushDecl(&f, decl_index);
+    {
+        var export_names = std.StringHashMapUnmanaged(void){};
+        defer export_names.deinit(gpa);
+        try export_names.ensureTotalCapacity(gpa, @intCast(u32, module.decl_exports.entries.len));
+        for (module.decl_exports.values()) |exports| for (exports.items) |@"export"|
+            try export_names.put(gpa, @"export".options.name, {});
+
+        while (f.remaining_decls.popOrNull()) |kv| {
+            const decl_index = kv.key;
+            try self.flushDecl(&f, decl_index, export_names);
+        }
     }
 
     f.all_buffers.items[typedef_index] = .{
@@ -415,7 +423,12 @@ fn flushErrDecls(self: *C, f: *Flush) FlushDeclError!void {
 }
 
 /// Assumes `decl` was in the `remaining_decls` set, and has already been removed.
-fn flushDecl(self: *C, f: *Flush, decl_index: Module.Decl.Index) FlushDeclError!void {
+fn flushDecl(
+    self: *C,
+    f: *Flush,
+    decl_index: Module.Decl.Index,
+    export_names: std.StringHashMapUnmanaged(void),
+) FlushDeclError!void {
     const module = self.base.options.module.?;
     const decl = module.declPtr(decl_index);
     // Before flushing any particular Decl we must ensure its
@@ -423,7 +436,7 @@ fn flushDecl(self: *C, f: *Flush, decl_index: Module.Decl.Index) FlushDeclError!
     // file comes out correctly.
     for (decl.dependencies.keys()) |dep| {
         if (f.remaining_decls.swapRemove(dep)) {
-            try flushDecl(self, f, dep);
+            try flushDecl(self, f, dep, export_names);
         }
     }
 
@@ -432,7 +445,8 @@ fn flushDecl(self: *C, f: *Flush, decl_index: Module.Decl.Index) FlushDeclError!
 
     try self.flushTypedefs(f, decl_block.typedefs);
     try f.all_buffers.ensureUnusedCapacity(gpa, 2);
-    f.appendBufAssumeCapacity(decl_block.fwd_decl.items);
+    if (!(decl.isExtern() and export_names.contains(mem.span(decl.name))))
+        f.appendBufAssumeCapacity(decl_block.fwd_decl.items);
 }
 
 pub fn flushEmitH(module: *Module) !void {