Merge pull request #13459 from ziglang/issue-13457

macho: do not zero-out file if there are no nonzerofill sects 

4 files changed, 29 insertions, 10 deletions

diff --git a/src/link/MachO/zld.zig b/src/link/MachO/zld.zig
index bccf1ec1d1..3a2ea79c6e 100644
--- a/src/link/MachO/zld.zig
+++ b/src/link/MachO/zld.zig
@@ -4300,24 +4300,21 @@ pub fn linkWithZld(macho_file: *MachO, comp: *Compilation, prog_node: *std.Progr
         // segment and the beginning of __LINKEDIT segment is zerofilled as the loader will
         // copy-paste this space into memory for quicker zerofill operation.
         if (zld.getSegmentByName("__DATA")) |data_seg_id| blk: {
-            var physical_zerofill_start: u64 = 0;
+            var physical_zerofill_start: ?u64 = null;
             const section_indexes = zld.getSectionIndexes(data_seg_id);
             for (zld.sections.items(.header)[section_indexes.start..section_indexes.end]) |header| {
                 if (header.isZerofill() and header.size > 0) break;
                 physical_zerofill_start = header.offset + header.size;
             } else break :blk;
+            const start = physical_zerofill_start orelse break :blk;
             const linkedit = zld.getLinkeditSegmentPtr();
-            const physical_zerofill_size = math.cast(usize, linkedit.fileoff - physical_zerofill_start) orelse
-                return error.Overflow;
-            if (physical_zerofill_size > 0) {
-                log.debug("zeroing out zerofill area of length {x} at {x}", .{
-                    physical_zerofill_size,
-                    physical_zerofill_start,
-                });
-                var padding = try zld.gpa.alloc(u8, physical_zerofill_size);
+            const size = math.cast(usize, linkedit.fileoff - start) orelse return error.Overflow;
+            if (size > 0) {
+                log.debug("zeroing out zerofill area of length {x} at {x}", .{ size, start });
+                var padding = try zld.gpa.alloc(u8, size);
                 defer zld.gpa.free(padding);
                 mem.set(u8, padding, 0);
-                try zld.file.pwriteAll(padding, physical_zerofill_start);
+                try zld.file.pwriteAll(padding, start);
             }
         }
 
diff --git a/test/link.zig b/test/link.zig
index c94dc2f4a0..9ad695ba26 100644
--- a/test/link.zig
+++ b/test/link.zig
@@ -79,6 +79,10 @@ fn addWasmCases(cases: *tests.StandaloneContext) void {
 }
 
 fn addMachOCases(cases: *tests.StandaloneContext) void {
+    cases.addBuildFile("test/link/macho/bugs/13457/build.zig", .{
+        .build_modes = true,
+    });
+
     cases.addBuildFile("test/link/macho/dead_strip/build.zig", .{
         .build_modes = false,
     });
diff --git a/test/link/macho/bugs/13457/build.zig b/test/link/macho/bugs/13457/build.zig
new file mode 100644
index 0000000000..2de8c01c6a
--- /dev/null
+++ b/test/link/macho/bugs/13457/build.zig
@@ -0,0 +1,17 @@
+const std = @import("std");
+const Builder = std.build.Builder;
+const LibExeObjectStep = std.build.LibExeObjStep;
+
+pub fn build(b: *Builder) void {
+    const mode = b.standardReleaseOptions();
+    const target: std.zig.CrossTarget = .{ .os_tag = .macos };
+
+    const test_step = b.step("test", "Test the program");
+
+    const exe = b.addExecutable("test", "main.zig");
+    exe.setBuildMode(mode);
+    exe.setTarget(target);
+
+    const run = exe.runEmulatable();
+    test_step.dependOn(&run.step);
+}
diff --git a/test/link/macho/bugs/13457/main.zig b/test/link/macho/bugs/13457/main.zig
new file mode 100644
index 0000000000..902b554db0
--- /dev/null
+++ b/test/link/macho/bugs/13457/main.zig
@@ -0,0 +1 @@
+pub fn main() void {}