debug/dwarf: better error message when reading absent debug_line_str

When a DW_FORM_line_strp is used without a debug_line_str section a
good error message (about the missing section) is generated but
immediately overwritten by the underflow error generated by trying to
read the non-existent section.

Updates #49590

Change-Id: I1c431392123a86c78c95ef1f185ebd6f17f2476a
Reviewed-on: https://go-review.googlesource.com/c/go/+/363894
Run-TryBot: Alessandro Arzilli <alessandro.arzilli@gmail.com>
Trust: David Chase <drchase@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>

diff --git a/src/debug/dwarf/entry.go b/src/debug/dwarf/entry.go
index 9f5ac570803d4c4d351633155f51ddb679eb617e..25a3b5beec3096addc785a6ed2ca78848626466c 100644 (file)
--- a/src/debug/dwarf/entry.go
+++ b/src/debug/dwarf/entry.go
@@ -641,6 +641,7 @@ func (b *buf) entry(cu *Entry, atab abbrevTable, ubase Offset, vers int) *Entry
                        } else {
                                if len(b.dwarf.lineStr) == 0 {
                                        b.error("DW_FORM_line_strp with no .debug_line_str section")
+                                       return nil
                                }
                                b1 = makeBuf(b.dwarf, b.format, "line_str", 0, b.dwarf.lineStr)
                        }