From 8eea5eddf773a8d1f9f883e71d00409e454ee0bd Mon Sep 17 00:00:00 2001
From: Jakub Konka <kubkon@jakubkonka.com>
Date: Fri, 14 May 2021 10:05:01 +0200
Subject: [PATCH] macho: fix bug with symbol growth and realloc

---
 src/link/MachO.zig     |  8 +++++++-
 test/stage2/darwin.zig | 29 ++++++++++++++++++++++++++++-
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/src/link/MachO.zig b/src/link/MachO.zig
index 2ae9575b7e..d8518c4894 100644
--- a/src/link/MachO.zig
+++ b/src/link/MachO.zig
@@ -1193,7 +1193,9 @@ pub fn updateDecl(self: *MachO, module: *Module, decl: *Module.Decl) !void {
         const need_realloc = code.len > capacity or !mem.isAlignedGeneric(u64, symbol.n_value, required_alignment);
         if (need_realloc) {
             const vaddr = try self.growTextBlock(&decl.link.macho, code.len, required_alignment);
-            log.debug("growing {s} from 0x{x} to 0x{x}", .{ decl.name, symbol.n_value, vaddr });
+
+            log.debug("growing {s} and moving from 0x{x} to 0x{x}", .{ decl.name, symbol.n_value, vaddr });
+
             if (vaddr != symbol.n_value) {
                 log.debug(" (writing new offset table entry)", .{});
                 self.offset_table.items[decl.link.macho.offset_table_index] = .{
@@ -1203,6 +1205,8 @@ pub fn updateDecl(self: *MachO, module: *Module, decl: *Module.Decl) !void {
                 };
                 try self.writeOffsetTableEntry(decl.link.macho.offset_table_index);
             }
+
+            symbol.n_value = vaddr;
         } else if (code.len < decl.link.macho.size) {
             self.shrinkTextBlock(&decl.link.macho, code.len);
         }
@@ -1219,7 +1223,9 @@ pub fn updateDecl(self: *MachO, module: *Module, decl: *Module.Decl) !void {
         const decl_name = mem.spanZ(decl.name);
         const name_str_index = try self.makeString(decl_name);
         const addr = try self.allocateTextBlock(&decl.link.macho, code.len, required_alignment);
+
         log.debug("allocated text block for {s} at 0x{x}", .{ decl_name, addr });
+
         errdefer self.freeTextBlock(&decl.link.macho);
 
         symbol.* = .{
diff --git a/test/stage2/darwin.zig b/test/stage2/darwin.zig
index 232bc42d25..f8d82391cc 100644
--- a/test/stage2/darwin.zig
+++ b/test/stage2/darwin.zig
@@ -41,7 +41,34 @@ pub fn addCases(ctx: *TestContext) !void {
                 "Hello, World!\n",
             );
 
-            // Now change the message only
+            // Print it 4 times and force growth and realloc.
+            case.addCompareOutput(
+                \\extern "c" fn write(usize, usize, usize) usize;
+                \\extern "c" fn exit(usize) noreturn;
+                \\
+                \\export fn _start() noreturn {
+                \\    print();
+                \\    print();
+                \\    print();
+                \\    print();
+                \\
+                \\    exit(0);
+                \\}
+                \\
+                \\fn print() void {
+                \\    const msg = @ptrToInt("Hello, World!\n");
+                \\    const len = 14;
+                \\    _ = write(1, msg, len);
+                \\}
+            ,
+                \\Hello, World!
+                \\Hello, World!
+                \\Hello, World!
+                \\Hello, World!
+                \\
+            );
+
+            // Print it once, and change the message.
             case.addCompareOutput(
                 \\extern "c" fn write(usize, usize, usize) usize;
                 \\extern "c" fn exit(usize) noreturn;