fix(debuginfo): Calculate line record sizes for DWARF (#220)

Calculates line record sizes for DWARF by comparing with the previous
row emitted from the line number program. Additionally, the sequence end
point is used to calculate the length for the last row/record.

debuginfo/src/base.rs

@@ -504,9 +504,15 @@ pub struct LineInfo<'data> {
 
 impl fmt::Debug for LineInfo<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_struct("LineInfo")
-            .field("address", &format_args!("{:#x}", self.address))
-            .field("file", &self.file)
+        let mut s = f.debug_struct("LineInfo");
+        s.field("address", &format_args!("{:#x}", self.address));
+
+        match self.size {
+            Some(size) => s.field("size", &format_args!("{:#x}", size)),
+            None => s.field("size", &self.size),
+        };
+
+        s.field("file", &self.file)
             .field("line", &self.line)
             .finish()
     }

debuginfo/src/dwarf.rs

@@ -176,6 +176,7 @@ struct DwarfRow {
     address: u64,
     file_index: u64,
     line: Option<u64>,
+    size: Option<u64>,
 }
 
 /// A sequence in the DWARF line program.
@@ -202,6 +203,13 @@ impl<'d, 'a> DwarfLineProgram<'d> {
 
         while let Ok(Some((_, &program_row))) = state_machine.next_row() {
             let address = program_row.address();
+
+            if let Some(last_row) = sequence_rows.last_mut() {
+                if address >= last_row.address {
+                    last_row.size = Some(address - last_row.address);
+                }
+            }
+
             if program_row.end_sequence() {
                 // Theoretically, there could be multiple DW_LNE_end_sequence in a row. We're not
                 // interested in empty sequences, so we can skip them completely.
@@ -242,6 +250,7 @@ impl<'d, 'a> DwarfLineProgram<'d> {
                         address,
                         file_index,
                         line,
+                        size: None,
                     });
                 }
                 prev_address = address;
@@ -557,7 +566,7 @@ impl<'d, 'a> DwarfUnit<'d, 'a> {
                 last = Some((row.file_index, line));
                 lines.push(LineInfo {
                     address: row.address - self.inner.info.load_address,
-                    size: None,
+                    size: row.size,
                     file,
                     line,
                 });