Merge pull request #460 from philipc/line-example

Add simple_line example

README.md

@@ -41,7 +41,9 @@ The minimum supported Rust version is 1.32.0.
 
 * Example programs:
 
-  * [A simple parser](./examples/simple.rs)
+  * [A simple `.debug_info` parser](./examples/simple.rs)
+
+  * [A simple `.debug_line` parser](./examples/simple_line.rs)
 
   * [A `dwarfdump` clone](./examples/dwarfdump.rs)
 

examples/simple.rs

@@ -1,8 +1,10 @@
+//! A simple example of parsing `.debug_info`.
+
 use object::Object;
 use std::{borrow, env, fs};
 
 fn main() {
-    for path in env::args() {
+    for path in env::args().skip(1) {
         let file = fs::File::open(&path).unwrap();
         let mmap = unsafe { memmap::Mmap::map(&file).unwrap() };
         let object = object::File::parse(&*mmap).unwrap();

examples/simple_line.rs

@@ -0,0 +1,96 @@
+//! A simple example of parsing `.debug_line`.
+
+use object::Object;
+use std::{borrow, env, fs, path};
+
+fn main() {
+    for path in env::args().skip(1) {
+        let file = fs::File::open(&path).unwrap();
+        let mmap = unsafe { memmap::Mmap::map(&file).unwrap() };
+        let object = object::File::parse(&*mmap).unwrap();
+        let endian = if object.is_little_endian() {
+            gimli::RunTimeEndian::Little
+        } else {
+            gimli::RunTimeEndian::Big
+        };
+        dump_file(&object, endian).unwrap();
+    }
+}
+
+fn dump_file(object: &object::File, endian: gimli::RunTimeEndian) -> Result<(), gimli::Error> {
+    // Load a section and return as `Cow<[u8]>`.
+    let load_section = |id: gimli::SectionId| -> Result<borrow::Cow<[u8]>, gimli::Error> {
+        Ok(object
+            .section_data_by_name(id.name())
+            .unwrap_or(borrow::Cow::Borrowed(&[][..])))
+    };
+    // Load a supplementary section. We don't have a supplementary object file,
+    // so always return an empty slice.
+    let load_section_sup = |_| Ok(borrow::Cow::Borrowed(&[][..]));
+
+    // Load all of the sections.
+    let dwarf_cow = gimli::Dwarf::load(&load_section, &load_section_sup)?;
+
+    // Borrow a `Cow<[u8]>` to create an `EndianSlice`.
+    let borrow_section: &dyn for<'a> Fn(
+        &'a borrow::Cow<[u8]>,
+    ) -> gimli::EndianSlice<'a, gimli::RunTimeEndian> =
+        &|section| gimli::EndianSlice::new(&*section, endian);
+
+    // Create `EndianSlice`s for all of the sections.
+    let dwarf = dwarf_cow.borrow(&borrow_section);
+
+    // Iterate over the compilation units.
+    let mut iter = dwarf.units();
+    while let Some(header) = iter.next()? {
+        println!(
+            "Line number info for unit at <.debug_info+0x{:x}>",
+            header.offset().0
+        );
+        let unit = dwarf.unit(header)?;
+
+        // Get the line program for the compilation unit.
+        if let Some(program) = unit.line_program.clone() {
+            let comp_dir = if let Some(ref dir) = unit.comp_dir {
+                path::PathBuf::from(dir.to_string_lossy().into_owned())
+            } else {
+                path::PathBuf::new()
+            };
+
+            // Iterate over the line program rows.
+            let mut rows = program.rows();
+            while let Some((header, row)) = rows.next_row()? {
+                if row.end_sequence() {
+                    // End of sequence indicates a possible gap in addresses.
+                    println!("{:x} end-sequence", row.address());
+                } else {
+                    // Determine the path. Real applications should cache this for performance.
+                    let mut path = path::PathBuf::new();
+                    if let Some(file) = row.file(header) {
+                        path = comp_dir.clone();
+                        if let Some(dir) = file.directory(header) {
+                            path.push(dwarf.attr_string(&unit, dir)?.to_string_lossy().as_ref());
+                        }
+                        path.push(
+                            dwarf
+                                .attr_string(&unit, file.path_name())?
+                                .to_string_lossy()
+                                .as_ref(),
+                        );
+                    }
+
+                    // Determine line/column. DWARF line/column is never 0, so we use that
+                    // but other applications may want to display this differently.
+                    let line = row.line().unwrap_or(0);
+                    let column = match row.column() {
+                        gimli::ColumnType::LeftEdge => 0,
+                        gimli::ColumnType::Column(x) => x,
+                    };
+
+                    println!("{:x} {}:{}:{}", row.address(), path.display(), line, column);
+                }
+            }
+        }
+    }
+    Ok(())
+}