fix: Macro segmentation faults (#6756)

* Fix for seg faults when using macros

* Update src/js_ast.zig to reflect review suggestions

Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>

* add test for checking non-zero exitcodes under macros. regression, issue 3830

---------

Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>

src/js_ast.zig

@@ -7278,8 +7278,9 @@ pub const Macro = struct {
 
             exception_holder = Zig.ZigException.Holder.init();
             var js_args: []JSC.JSValue = &.{};
+            var js_processed_args_len: usize = 0;
             defer {
-                for (js_args[0 .. js_args.len - @as(usize, @intFromBool(!javascript_object.isEmpty()))]) |arg| {
+                for (js_args[0..js_processed_args_len -| @as(usize, @intFromBool(!javascript_object.isEmpty()))]) |arg| {
                     arg.unprotect();
                 }
 
@@ -7292,12 +7293,18 @@ pub const Macro = struct {
                 .e_call => |call| {
                     const call_args: []Expr = call.args.slice();
                     js_args = try allocator.alloc(JSC.JSValue, call_args.len + @as(usize, @intFromBool(!javascript_object.isEmpty())));
+                    js_processed_args_len = js_args.len;
 
-                    for (call_args, js_args[0..call_args.len]) |in, *out| {
-                        const value = try in.toJS(
+                    for (0.., call_args, js_args[0..call_args.len]) |i, in, *out| {
+                        const value = in.toJS(
                             allocator,
                             globalObject,
-                        );
+                        ) catch |e| {
+                            // Keeping a separate variable instead of modifying js_args.len
+                            // due to allocator.free call in defer
+                            js_processed_args_len = i;
+                            return e;
+                        };
                         value.protect();
                         out.* = value;
                     }

src/js_parser.zig

@@ -16389,7 +16389,7 @@ fn NewParser_(
                                         p.log.addError(p.source, expr.loc, "macro threw exception") catch unreachable;
                                     }
                                 } else {
-                                    p.log.addErrorFmt(p.source, expr.loc, p.allocator, "{s} error in macro", .{@errorName(err)}) catch unreachable;
+                                    p.log.addErrorFmt(p.source, expr.loc, p.allocator, "\"{s}\" error in macro", .{@errorName(err)}) catch unreachable;
                                 }
                                 return expr;
                             };

test/regression/issue/03830.test.ts

@@ -0,0 +1,30 @@
+// test/regression/issue/03830.test.ts
+
+import { it, expect } from "bun:test";
+import { bunEnv, bunExe } from "harness";
+import { mkdirSync, rmSync, writeFileSync, readFileSync, mkdtempSync } from "fs";
+import { tmpdir } from "os";
+import { join } from "path";
+
+it("macros should not lead to seg faults under any given input", async () => {
+    // this test code follows the same structure as and 
+    // is based on the code for testing issue 4893
+
+    const testDir = mkdtempSync(join(tmpdir(), "issue3830-"));
+
+    // Clean up from prior runs if necessary
+    rmSync(testDir, { recursive: true, force: true });
+
+    // Create a directory with our test file
+    mkdirSync(testDir, { recursive: true });
+    writeFileSync(join(testDir, "macro.ts"), 'export function fn(str) { return str; }');
+    writeFileSync(join(testDir, "index.ts"), "import { fn } from './macro' assert { type: 'macro' };\nfn(`©${''}`);");
+
+    const { stdout, exitCode } = Bun.spawnSync({
+        cmd: [bunExe(), "build", join(testDir, "index.ts")],
+        env: bunEnv,
+        stderr: "inherit",
+    });
+
+    expect(exitCode).toBe(0);
+});