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link/MachO: fixes to debug symbols

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commitDeclDebugInfo: stop trying to write length 0 debug info - avoids
hitting an error where zig tries to move the debug info section
unnecessarily, gets confused, and reports `error.InputOutput`.

The 2 pieces of code that looked at the source and tried to compute
source line offsets is now improved to match link/Elf - use the
line/column data stored in the Decl object to skip the costly scanning
of source bytes. No need to load Zig source code, AST, or tokens, when
we have the ZIR!
This commit is contained in:
Andrew Kelley 2021-05-13 20:05:41 -07:00
parent 78632894da
commit edab03bc22
1 changed files with 8 additions and 24 deletions
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32
src/link/MachO/DebugSymbols.zig
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@ -909,20 +909,14 @@ pub fn updateDeclLineNumber(self: *DebugSymbols, module: *Module, decl: *const M
const node_datas = tree.nodes.items(.data);
const token_starts = tree.tokens.items(.start);
// TODO Look into improving the performance here by adding a token-index-to-line
// lookup table. Currently this involves scanning over the source code for newlines.
const fn_decl = decl.src_node;
assert(node_tags[fn_decl] == .fn_decl);
const block = node_datas[fn_decl].rhs;
const lbrace = tree.firstToken(block);
const line_delta = std.zig.lineDelta(tree.source, 0, token_starts[lbrace]);
const casted_line_off = @intCast(u28, line_delta);
const func = decl.val.castTag(.function).?.data;
const line_off = @intCast(u28, decl.src_line + func.lbrace_line);
const dwarf_segment = &self.load_commands.items[self.dwarf_segment_cmd_index.?].Segment;
const shdr = &dwarf_segment.sections.items[self.debug_line_section_index.?];
const file_pos = shdr.offset + decl.fn_link.macho.off + getRelocDbgLineOff();
var data: [4]u8 = undefined;
leb.writeUnsignedFixed(4, &data, casted_line_off);
leb.writeUnsignedFixed(4, &data, line_off);
try self.file.pwriteAll(&data, file_pos);
}
@ -952,21 +946,8 @@ pub fn initDeclDebugBuffers(
// For functions we need to add a prologue to the debug line program.
try dbg_line_buffer.ensureCapacity(26);
const line_off: u28 = blk: {
const tree = decl.namespace.file_scope.tree;
const node_tags = tree.nodes.items(.tag);
const node_datas = tree.nodes.items(.data);
const token_starts = tree.tokens.items(.start);
// TODO Look into improving the performance here by adding a token-index-to-line
// lookup table. Currently this involves scanning over the source code for newlines.
const fn_decl = decl.src_node;
assert(node_tags[fn_decl] == .fn_decl);
const block = node_datas[fn_decl].rhs;
const lbrace = tree.firstToken(block);
const line_delta = std.zig.lineDelta(tree.source, 0, token_starts[lbrace]);
break :blk @intCast(u28, line_delta);
};
const func = decl.val.castTag(.function).?.data;
const line_off = @intCast(u28, decl.src_line + func.lbrace_line);
dbg_line_buffer.appendSliceAssumeCapacity(&[_]u8{
DW.LNS_extended_op,
@ -1162,6 +1143,9 @@ pub fn commitDeclDebugInfo(
else => {},
}
if (dbg_info_buffer.items.len == 0)
return;
// Now we emit the .debug_info types of the Decl. These will count towards the size of
// the buffer, so we have to do it before computing the offset, and we can't perform the actual
// relocations yet.