diff options
Diffstat (limited to 'src/cmd/internal/obj/dwarf.go')
| -rw-r--r-- | src/cmd/internal/obj/dwarf.go | 46 |
1 files changed, 23 insertions, 23 deletions
diff --git a/src/cmd/internal/obj/dwarf.go b/src/cmd/internal/obj/dwarf.go index 4118c6442c..cd1d5b8687 100644 --- a/src/cmd/internal/obj/dwarf.go +++ b/src/cmd/internal/obj/dwarf.go @@ -44,14 +44,12 @@ func (ctxt *Link) generateDebugLinesSymbol(s, lines *LSym) { } } - // Set up the debug_lines state machine. - // NB: This state machine is reset to this state when we've finished - // generating the line table. See below. - // TODO: Once delve can support multiple DW_LNS_end_statements, we don't have - // to do this. + // Set up the debug_lines state machine to the default values + // we expect at the start of a new sequence. stmt := true line := int64(1) pc := s.Func.Text.Pc + var lastpc int64 // last PC written to line table, not last PC in func name := "" prologue, wrotePrologue := false, false // Walk the progs, generating the DWARF table. @@ -86,30 +84,32 @@ func (ctxt *Link) generateDebugLinesSymbol(s, lines *LSym) { if line != int64(newLine) || wrote { pcdelta := p.Pc - pc + lastpc = p.Pc putpclcdelta(ctxt, dctxt, lines, uint64(pcdelta), int64(newLine)-line) line, pc = int64(newLine), p.Pc } } - // Because these symbols will be concatenated together by the linker, we need - // to reset the state machine that controls the debug symbols. The fields in - // the state machine that need to be reset are: - // file = 1 - // line = 1 - // column = 0 - // stmt = set in header, we assume true - // basic_block = false - // Careful readers of the DWARF specification will note that we don't reset - // the address of the state machine -- but this will happen at the beginning - // of the NEXT block of opcodes. - dctxt.AddUint8(lines, dwarf.DW_LNS_set_file) + // Because these symbols will be concatenated together by the + // linker, we need to reset the state machine that controls the + // debug symbols. Do this using an end-of-sequence operator. + // + // Note: at one point in time, Delve did not support multiple end + // sequence ops within a compilation unit (bug for this: + // https://github.com/go-delve/delve/issues/1694), however the bug + // has since been fixed (Oct 2019). + // + // Issue 38192: the DWARF standard specifies that when you issue + // an end-sequence op, the PC value should be one past the last + // text address in the translation unit, so apply a delta to the + // text address before the end sequence op. If this isn't done, + // GDB will assign a line number of zero the last row in the line + // table, which we don't want. + lastlen := uint64(s.Size - (lastpc - s.Func.Text.Pc)) + putpclcdelta(ctxt, dctxt, lines, lastlen, 0) + dctxt.AddUint8(lines, 0) // start extended opcode dwarf.Uleb128put(dctxt, lines, 1) - dctxt.AddUint8(lines, dwarf.DW_LNS_advance_line) - dwarf.Sleb128put(dctxt, lines, int64(1-line)) - if !stmt { - dctxt.AddUint8(lines, dwarf.DW_LNS_negate_stmt) - } - dctxt.AddUint8(lines, dwarf.DW_LNS_copy) + dctxt.AddUint8(lines, dwarf.DW_LNE_end_sequence) } func putpclcdelta(linkctxt *Link, dctxt dwCtxt, s *LSym, deltaPC uint64, deltaLC int64) { |