From 742aa942800e81b14ac1fc6d9a8b3cc33621e2b6 Mon Sep 17 00:00:00 2001
From: Jakub Konka <kubkon@jakubkonka.com>
Date: Thu, 8 Dec 2022 14:24:10 +0100
Subject: [PATCH] dsym: hint linker when file range copy is not necessary

---
 src/link/Dwarf.zig              | 10 +++++-----
 src/link/MachO/DebugSymbols.zig | 20 +++++++++++---------
 2 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/src/link/Dwarf.zig b/src/link/Dwarf.zig
index e804871c67..7e0cbb0358 100644
--- a/src/link/Dwarf.zig
+++ b/src/link/Dwarf.zig
@@ -1166,7 +1166,7 @@ pub fn commitDeclState(
                 .macho => {
                     const d_sym = self.bin_file.cast(File.MachO).?.getDebugSymbols().?;
                     const sect_index = d_sym.debug_line_section_index.?;
-                    try d_sym.growSection(sect_index, needed_size);
+                    try d_sym.growSection(sect_index, needed_size, true);
                     const sect = d_sym.getSection(sect_index);
                     const file_pos = sect.offset + src_fn.off;
                     try pwriteDbgLineNops(
@@ -1414,7 +1414,7 @@ fn writeDeclDebugInfo(self: *Dwarf, atom: *Atom, dbg_info_buf: []const u8) !void
         .macho => {
             const d_sym = self.bin_file.cast(File.MachO).?.getDebugSymbols().?;
             const sect_index = d_sym.debug_info_section_index.?;
-            try d_sym.growSection(sect_index, needed_size);
+            try d_sym.growSection(sect_index, needed_size, true);
             const sect = d_sym.getSection(sect_index);
             const file_pos = sect.offset + atom.off;
             try pwriteDbgInfoNops(
@@ -1697,7 +1697,7 @@ pub fn writeDbgAbbrev(self: *Dwarf) !void {
         .macho => {
             const d_sym = self.bin_file.cast(File.MachO).?.getDebugSymbols().?;
             const sect_index = d_sym.debug_abbrev_section_index.?;
-            try d_sym.growSection(sect_index, needed_size);
+            try d_sym.growSection(sect_index, needed_size, false);
             const sect = d_sym.getSection(sect_index);
             const file_pos = sect.offset + abbrev_offset;
             try d_sym.file.pwriteAll(&abbrev_buf, file_pos);
@@ -2134,7 +2134,7 @@ pub fn writeDbgAranges(self: *Dwarf, addr: u64, size: u64) !void {
         .macho => {
             const d_sym = self.bin_file.cast(File.MachO).?.getDebugSymbols().?;
             const sect_index = d_sym.debug_aranges_section_index.?;
-            try d_sym.growSection(sect_index, needed_size);
+            try d_sym.growSection(sect_index, needed_size, false);
             const sect = d_sym.getSection(sect_index);
             const file_pos = sect.offset;
             try d_sym.file.pwriteAll(di_buf.items, file_pos);
@@ -2301,7 +2301,7 @@ pub fn writeDbgLineHeader(self: *Dwarf, module: *Module) !void {
                 const d_sym = self.bin_file.cast(File.MachO).?.getDebugSymbols().?;
                 const sect_index = d_sym.debug_line_section_index.?;
                 const needed_size = @intCast(u32, d_sym.getSection(sect_index).size + delta);
-                try d_sym.growSection(sect_index, needed_size);
+                try d_sym.growSection(sect_index, needed_size, true);
                 const file_pos = d_sym.getSection(sect_index).offset + src_fn.off;
 
                 const amt = try d_sym.file.preadAll(buffer, file_pos);
diff --git a/src/link/MachO/DebugSymbols.zig b/src/link/MachO/DebugSymbols.zig
index 6a6bea998e..7fa4a8f4dd 100644
--- a/src/link/MachO/DebugSymbols.zig
+++ b/src/link/MachO/DebugSymbols.zig
@@ -147,7 +147,7 @@ fn allocateSection(self: *DebugSymbols, sectname: []const u8, size: u64, alignme
     return index;
 }
 
-pub fn growSection(self: *DebugSymbols, sect_index: u8, needed_size: u32) !void {
+pub fn growSection(self: *DebugSymbols, sect_index: u8, needed_size: u32, requires_file_copy: bool) !void {
     const sect = self.getSectionPtr(sect_index);
 
     if (needed_size > self.allocatedSize(sect.offset)) {
@@ -162,13 +162,15 @@ pub fn growSection(self: *DebugSymbols, sect_index: u8, needed_size: u32) !void
             new_offset,
         });
 
-        const amt = try self.file.copyRangeAll(
-            sect.offset,
-            self.file,
-            new_offset,
-            existing_size,
-        );
-        if (amt != existing_size) return error.InputOutput;
+        if (requires_file_copy) {
+            const amt = try self.file.copyRangeAll(
+                sect.offset,
+                self.file,
+                new_offset,
+                existing_size,
+            );
+            if (amt != existing_size) return error.InputOutput;
+        }
 
         sect.offset = @intCast(u32, new_offset);
     }
@@ -287,7 +289,7 @@ pub fn flushModule(self: *DebugSymbols, macho_file: *MachO) !void {
         const sect_index = self.debug_str_section_index.?;
         if (self.debug_string_table_dirty or self.dwarf.strtab.items.len != self.getSection(sect_index).size) {
             const needed_size = @intCast(u32, self.dwarf.strtab.items.len);
-            try self.growSection(sect_index, needed_size);
+            try self.growSection(sect_index, needed_size, false);
             try self.file.pwriteAll(self.dwarf.strtab.items, self.getSection(sect_index).offset);
             self.debug_string_table_dirty = false;
         }