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.debug_line: avoid DW_FORM_strp to work around readelf/gdb

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These tools do not support DWARFv5 yet apparently.
This commit is contained in:
Andrew Kelley 2020-08-02 20:22:41 -07:00
parent 1ce6e201aa
commit 42d331b58a
1 changed files with 27 additions and 11 deletions
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38
src-self-hosted/link.zig
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@ -1264,27 +1264,37 @@ pub const File = struct {
1, // `DW.LNS_set_isa`
1, // directory_entry_format_count
DW.LNCT_path, DW.FORM_strp, // directory_entry_format
DW.LNCT_path, DW.FORM_string, // directory_entry_format
// For now we only support one compilation unit, which has one directory.
1, // directories_count (this is a ULEB128)
});
const comp_dir_strp = try self.makeDebugString(self.base.options.root_pkg.root_src_dir_path);
self.writeDwarfAddrAssumeCapacity(&di_buf, comp_dir_strp);
// Empirically, some tools do not understand DW.FORM_strp yet. readelf 2.31.1 gives the bogus
// error <no .debug_str section> and gdb 8.3.1 crashes. Both programs seem to work fine with
// DW.FORM_string however.
di_buf.appendSliceAssumeCapacity(self.base.options.root_pkg.root_src_dir_path);
di_buf.appendAssumeCapacity(0);
di_buf.appendSliceAssumeCapacity(&[_]u8{
2, // file_name_entry_format_count
DW.LNCT_path, DW.FORM_strp, // file_name_entry_format[0]
DW.LNCT_path, DW.FORM_string, // file_name_entry_format[0]
DW.LNCT_directory_index, DW.FORM_data1, // file_name_entry_format[1]
// TODO Look into adding the file size here. Maybe even the mtime and MD5.
//DW.LNCT_size, DW.FORM_udata, // file_name_entry_format[2]
// For now we only put the root file name here. Once more source files
// are supported, this will need to be improved.
1, // file_names_count (this is a ULEB128)
2, // file_names_count (this is a ULEB128)
});
const root_src_file_strp = try self.makeDebugString(self.base.options.root_pkg.root_src_path);
self.writeDwarfAddrAssumeCapacity(&di_buf, root_src_file_strp); // DW.LNCT_path, DW.FORM_strp
// See note above with directories about why we use DW.FORM_string here.
di_buf.appendSliceAssumeCapacity(self.base.options.root_pkg.root_src_path);
di_buf.appendAssumeCapacity(0);
di_buf.appendAssumeCapacity(0); // LNCT_directory_index, FORM_data1
// We add the root file twice because according to DWARF, the state machine
// starts out with file index 1.
di_buf.appendSliceAssumeCapacity(self.base.options.root_pkg.root_src_path);
di_buf.appendAssumeCapacity(0);
di_buf.appendAssumeCapacity(0); // LNCT_directory_index, FORM_data1
const header_len = di_buf.items.len - after_header_len;
@ -2140,8 +2150,9 @@ pub const File = struct {
{
var header: [dbg_line_file_header_len]u8 = undefined;
header[0] = DW.LNS_set_file;
// Once we support more than one source file, this will have the ability to be non-zero.
const file_index = 0;
// Once we support more than one source file, this will have the ability to be more
// than one possible value.
const file_index = 1;
leb128.writeUnsignedFixed(4, header[1..5], file_index);
try self.file.?.pwriteAll(&header, header_off);
}
@ -2384,8 +2395,13 @@ pub const File = struct {
const file_name_entry_format_count = 1;
const directory_count = 1;
const file_name_count = 1;
return 53 + directory_entry_format_count * 2 + file_name_entry_format_count * 2 +
directory_count * 8 + file_name_count * 8;
return @intCast(u32, 53 + directory_entry_format_count * 2 + file_name_entry_format_count * 2 +
directory_count * 8 + file_name_count * 8 +
// These are encoded as DW.FORM_string rather than DW.FORM_strp as we would like
// because of a workaround for readelf and gdb failing to understand DWARFv5 correctly.
self.base.options.root_pkg.root_src_dir_path.len +
self.base.options.root_pkg.root_src_path.len * 2);
}
};
};