overhaul target handling

3 files changed, 487 insertions, 135 deletions

diff --git a/src/main.rs b/src/main.rs
index 4048886..2764e97 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -26,10 +26,6 @@ fn main() {
     // TODO dump command-line macros into environment
     // TODO add SHELL macro
     let mut makefile = Makefile::new(args.clone());
-    if !args.no_builtin_rules {
-        makefile.add_builtins();
-    }
-    makefile.add_env();
     for filename in &args.makefile {
         if filename == &PathBuf::from("-") {
             makefile.and_read(stdin().lock());
@@ -37,4 +33,18 @@ fn main() {
             makefile.and_read_file(filename);
         };
     }
+
+    if args.print_everything {
+        println!("{}", &makefile);
+    }
+
+    let targets = if args.targets().count() == 0 {
+        vec![makefile.first_non_special_target.clone().expect("couldn't find a target!")]
+    } else {
+        args.targets().cloned().collect()
+    };
+
+    for target in targets {
+        makefile.update_target(&target);
+    }
 }
diff --git a/src/makefile/mod.rs b/src/makefile/mod.rs
index 75873d2..e8adac9 100644
--- a/src/makefile/mod.rs
+++ b/src/makefile/mod.rs
@@ -1,8 +1,11 @@
+use std::cell::{Cell, RefCell};
 use std::collections::HashMap;
 use std::env;
+use std::fmt;
 use std::fs::{File, metadata};
 use std::io::{BufRead, BufReader};
 use std::path::Path;
+use std::rc::Rc;
 use std::time::SystemTime;
 
 use lazy_static::lazy_static;
@@ -14,31 +17,22 @@ mod token;
 
 use token::{tokenize, Token, TokenString};
 
-pub enum RuleType {
-    Inference,
-    Target,
-}
-
 #[derive(PartialEq, Eq, Clone)]
-pub struct Rule {
-    name: String,
-    prerequisites: Vec<String>,
+pub struct InferenceRule {
+    /// POSIX calls this ".s1" but that's not useful.
+    product: String,
+    /// POSIX calls this ".s2" but that's not useful.
+    prereq: String,
     commands: Vec<CommandLine>,
 }
 
-impl Rule {
-    pub fn r#type(&self) -> RuleType {
-        if self.name.contains(".") && !self.name.contains("/") {
-            RuleType::Inference
-        } else {
-            RuleType::Target
-        }
-    }
-
-    fn execute_commands(&self, file: &Makefile, target: &Target) {
+impl fmt::Display for InferenceRule {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        writeln!(f, "{}{}:", &self.prereq, &self.product)?;
         for command in &self.commands {
-            command.execute(file, target);
+            writeln!(f, "\t{}", command)?;
         }
+        Ok(())
     }
 }
 
@@ -46,8 +40,8 @@ impl Rule {
 pub struct Target {
     name: String,
     prerequisites: Vec<String>,
-    rule: Option<Rule>,
-    already_updated: bool,
+    commands: Vec<CommandLine>,
+    already_updated: Cell<bool>,
 }
 
 impl Target {
@@ -58,45 +52,55 @@ impl Target {
     }
 
     fn newer_than(&self, other: &Target) -> Option<bool> {
+        let self_updated = self.already_updated.get();
+        let other_updated = other.already_updated.get();
         Some(match (self.modified_time(), other.modified_time()) {
             (Some(self_mtime), Some(other_mtime)) => self_mtime >= other_mtime,
             // per POSIX: "If the target does not exist after the target has been
             // successfully made up-to-date, the target shall be treated as being
             // newer than any target for which it is a prerequisite."
-            (None, _) if self.already_updated && other.prerequisites.contains(&self.name) => true,
-            (_, None) if other.already_updated && self.prerequisites.contains(&other.name) => false,
+            (None, _) if self_updated && other.prerequisites.contains(&self.name) => true,
+            (_, None) if other_updated && self.prerequisites.contains(&other.name) => false,
             _ => return None,
         })
     }
 
-    fn is_up_to_date(&self, file: &mut Makefile) -> bool {
-        if self.already_updated {
+    fn is_up_to_date(&self, file: &Makefile) -> bool {
+        if self.already_updated.get() {
             return true;
         }
         let exists = metadata(&self.name).is_ok();
-        if exists && self.rule.is_none() {
-            return true;
-        }
         let newer_than_all_dependencies = self.prerequisites
             .iter()
-            .all(|t| self.newer_than(&file.get_target(t)).unwrap_or(false));
-        if exists && newer_than_all_dependencies {
-            return true;
-        }
-        false
+            .all(|t| self.newer_than(&file.get_target(t).borrow()).unwrap_or(false));
+        exists && newer_than_all_dependencies
     }
 
-    fn update(&mut self, file: &mut Makefile) {
+    pub fn update(&self, file: &Makefile) {
         for prereq in &self.prerequisites {
             file.update_target(prereq);
         }
         if !self.is_up_to_date(file) {
-            match &self.rule {
-                Some(rule) => rule.execute_commands(file, self),
-                None => panic!("target doesn't exist & no rule to make it"), // TODO handle this error well
-            }
+            self.execute_commands(file);
+        }
+        self.already_updated.set(true);
+    }
+
+    fn execute_commands(&self, file: &Makefile) {
+        for command in &self.commands {
+            command.execute(file, self);
         }
-        self.already_updated = true;
+    }
+}
+
+impl fmt::Display for Target {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let prereqs = self.prerequisites.join(" ");
+        writeln!(f, "{}: {}", &self.name, prereqs)?;
+        for command in &self.commands {
+            writeln!(f, "\t{}", command)?;
+        }
+        Ok(())
     }
 }
 
@@ -148,28 +152,29 @@ impl CommandLine {
     }
 
     fn execute(&self, file: &Makefile, target: &Target) {
+        let ignore_error = self.ignore_errors ||
+            file.args.ignore_errors ||
+            file.special_target_has_prereq(".IGNORE", &target.name);
+        let silent = (self.silent && !file.args.dry_run) ||
+            file.args.silent ||
+            file.special_target_has_prereq(".SILENT", &target.name);
+
+        let execution_line = file.expand_macros(&self.execution_line, Some(target));
+
         let avoid_execution = file.args.dry_run || file.args.question || file.args.touch;
         if avoid_execution && !self.always_execute {
             return;
         }
 
-        let execution_line = file.expand_macros(&self.execution_line);
-
-        let self_silent = self.silent && !file.args.dry_run;
-        let special_target_silent = file.rules.get(".SILENT")
-            .map_or(false, |silent_target| {
-                silent_target.prerequisites.is_empty() || silent_target.prerequisites.contains(&target.name)
-            });
-        let silent = self_silent || file.args.silent || special_target_silent;
         if !silent {
             println!("{}", execution_line);
         }
 
-        let special_target_ignore = file.rules.get(".IGNORE")
-            .map_or(false, |ignore_target| {
-                ignore_target.prerequisites.is_empty() || ignore_target.prerequisites.contains(&target.name)
-            });
-        let ignore_error = self.ignore_errors || file.args.ignore_errors || special_target_ignore;
+        let should_execute = self.always_execute ||
+            !(file.args.dry_run || file.args.question || file.args.touch);
+        if !should_execute {
+            return;
+        }
 
         // TODO don't fuck this up
         let execution_line = ::std::ffi::CString::new(execution_line.as_bytes())
@@ -186,6 +191,24 @@ impl CommandLine {
     }
 }
 
+impl fmt::Display for CommandLine {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        if self.ignore_errors {
+            write!(f, "-")?;
+        }
+        if self.silent {
+            write!(f, "@")?;
+        }
+        if self.always_execute {
+            write!(f, "+")?;
+        }
+        let execution_line = format!("{}", &self.execution_line);
+        let execution_line = execution_line.replace("\n", "↵\n");
+        writeln!(f, "{}", execution_line)?;
+        Ok(())
+    }
+}
+
 enum MacroSource {
     File,
     CommandLineOrMAKEFLAGS,
@@ -194,38 +217,53 @@ enum MacroSource {
 }
 
 pub struct Makefile {
-    rules: HashMap<String, Rule>,
+    inference_rules: Vec<InferenceRule>,
     macros: HashMap<String, (MacroSource, TokenString)>,
-    targets: HashMap<String, Target>,
+    targets: RefCell<HashMap<String, Rc<RefCell<Target>>>>,
+    pub first_non_special_target: Option<String>,
     args: Args,
+    // TODO borrow warnings from Python version
 }
 
 impl Makefile {
     pub fn new(args: Args) -> Makefile {
-        Makefile {
-            rules: HashMap::new(),
-            macros: HashMap::new(),
-            targets: HashMap::new(),
-            args,
+        let mut inference_rules = vec![];
+        let mut macros = HashMap::new();
+        let mut targets = HashMap::new();
+        let first_non_special_target = None;
+
+        if !args.no_builtin_rules {
+            inference_rules.extend(builtin_inference_rules());
+            for (k, v) in builtin_macros() {
+                macros.insert(k.into(), (MacroSource::Builtin, v));
+            }
+            targets.extend(builtin_targets().into_iter()
+                .map(|t| (t.name.clone(), Rc::new(RefCell::new(t)))));
         }
-    }
 
-    pub fn add_builtins(&mut self) -> &mut Makefile {
-        self.rules.extend(BUILTIN_RULES.iter().map(|(name, rule)| (name.to_string(), rule.clone())));
-        self
-    }
+        for (k, v) in env::vars() {
+            if k != "MAKEFLAGS" && k != "SHELL" {
+                macros.insert(k, (MacroSource::Environment, TokenString::text(v)));
+            }
+        }
 
-    pub fn add_env(&mut self) -> &mut Makefile {
-        self.macros.extend(env::vars()
-            .filter_map(|(name, value)| {
-                if name == "MAKEFLAGS" || name == "SHELL" {
-                    None
-                } else {
-                    Some((name, (MacroSource::Environment, TokenString::from(vec![Token::Text(value)]))))
+        for r#macro in args.macros() {
+            let pieces = r#macro.splitn(2, '=').collect::<Vec<_>>();
+            match *pieces {
+                [name, value] => {
+                    macros.insert(name.into(), (MacroSource::CommandLineOrMAKEFLAGS, TokenString::text(value)));
                 }
-            })
-        );
-        self
+                _ => {}
+            }
+        }
+
+        Makefile {
+            inference_rules,
+            macros,
+            targets: RefCell::new(targets),
+            first_non_special_target,
+            args,
+        }
     }
 
     pub fn and_read_file(&mut self, path: impl AsRef<Path>) -> &mut Makefile {
@@ -248,7 +286,7 @@ impl Makefile {
             // TODO handle I/O errors at all
             let mut line = line.expect("failed to read line of makefile!");
 
-            // handle escaped newlines (TODO exception for command lines)
+            // handle escaped newlines
             while line.ends_with(r"\") {
                 let next_line = match lines_iter.next() {
                     Some(x) => x,
@@ -256,9 +294,11 @@ impl Makefile {
                 };
                 let next_line = next_line.expect("failed to read line of makefile!");
                 let next_line = next_line.trim_start();
+                line.pop();
                 line.push(' ');
                 line.push_str(next_line);
             }
+
             // handle comments
             lazy_static! {
                 static ref COMMENT: Regex = Regex::new("#.*$").unwrap();
@@ -269,11 +309,10 @@ impl Makefile {
             if let Some(line) = line.strip_prefix("include ") {
                 // remove extra leading space
                 let line = line.trim_start();
-                let line = self.expand_macros(&tokenize(line));
+                let line = self.expand_macros(&tokenize(line), None);
                 let fields = line.split_whitespace();
                 // POSIX says we only have to handle a single filename, but GNU make
                 // handles arbitrarily many filenames, and it's not like that's more work
-                // TODO have some way of linting for non-portable constructs
                 for field in fields {
                     self.and_read_file(field);
                 }
@@ -322,18 +361,34 @@ impl Makefile {
                 match line_type {
                     LineType::Rule => {
                         let (targets, not_targets) = line_tokens.split_once(':').unwrap();
-                        let targets = self.expand_macros(&targets);
+                        let targets = self.expand_macros(&targets, None);
                         let targets = targets.split_whitespace().map(|x| x.into()).collect::<Vec<String>>();
                         let (prerequisites, mut commands) = match not_targets.split_once(';') {
-                            Some((prerequisites, commands)) => (prerequisites, vec![commands]),
+                            Some((prerequisites, mut command)) => {
+                                while command.ends_with(r"\") && lines_iter.peek().is_some() {
+                                    command.strip_suffix(r"\");
+                                    command.extend(tokenize(&lines_iter.next().unwrap().unwrap()));
+                                }
+                                (prerequisites, vec![command])
+                            }
                             None => (not_targets, vec![]),
                         };
-                        let prerequisites = self.expand_macros(&prerequisites);
+                        let prerequisites = self.expand_macros(&prerequisites, None);
                         let prerequisites = prerequisites.split_whitespace().map(|x| x.into()).collect::<Vec<String>>();
 
                         while lines_iter.peek().and_then(|x| x.as_ref().ok()).map_or(false, |line| line.starts_with('\t')) {
                             let line = lines_iter.next().unwrap().unwrap();
-                            let line = line.strip_prefix("\t").unwrap();
+                            let mut line: String = line.strip_prefix("\t").unwrap().into();
+                            while line.ends_with('\\') {
+                                match lines_iter.next() {
+                                    Some(Ok(next_line)) => {
+                                        let next_line = next_line.strip_prefix("\t").unwrap_or(&next_line);
+                                        line.push('\n');
+                                        line.push_str(next_line);
+                                    }
+                                    _ => break
+                                }
+                            }
                             commands.push(line.parse().unwrap());
                         }
 
@@ -341,32 +396,110 @@ impl Makefile {
                             .map(CommandLine::from)
                             .collect::<Vec<_>>();
 
-                        for target in targets {
-                            match self.rules.get_mut(&target) {
-                                Some(old_rule) if commands.is_empty() => {
-                                    old_rule.prerequisites.extend(prerequisites.clone());
+                        if targets.is_empty() {
+                            continue;
+                        }
+
+                        // we don't know yet if it's a target rule or an inference rule
+                        lazy_static! {
+                            static ref INFERENCE_RULE: Regex = Regex::new(r"^(?P<s2>(\.[^/.]+)?)(?P<s1>\.[^/.]+)$").unwrap();
+                            static ref SPECIAL_TARGET: Regex = Regex::new(r"^\.[A-Z]+$").unwrap();
+                        }
+
+                        let inference_match = INFERENCE_RULE.captures(&targets[0]);
+                        let special_target_match = SPECIAL_TARGET.captures(&targets[0]);
+
+                        let inference_rule = targets.len() == 1 && prerequisites.len() == 0 && inference_match.is_some() && special_target_match.is_none();
+                        if inference_rule {
+                            let inference_match = inference_match.unwrap();
+                            let new_rule = InferenceRule {
+                                product: inference_match.name("s1").unwrap().as_str().to_string(),
+                                prereq: inference_match.name("s2").unwrap().as_str().to_string(),
+                                commands,
+                            };
+
+                            self.inference_rules.retain(|existing_rule|
+                                (&existing_rule.prereq, &existing_rule.product) != (&new_rule.prereq, &new_rule.product));
+                            self.inference_rules.push(new_rule);
+                        } else {
+                            for target in targets {
+                                if self.first_non_special_target.is_none() && !target.starts_with('.') {
+                                    self.first_non_special_target = Some(target.clone());
                                 }
-                                _ => {
-                                    self.rules.insert(target.clone(), Rule {
-                                        name: target,
-                                        prerequisites: prerequisites.clone(),
-                                        commands: commands.clone(),
-                                    });
+                                let mut targets = self.targets.borrow_mut();
+                                match targets.get_mut(&target) {
+                                    Some(old_target) if commands.is_empty() && !(target == ".SUFIXES" && prerequisites.is_empty()) => {
+                                        let mut old_target = old_target.borrow_mut();
+                                        let new_prerequisites = prerequisites.iter()
+                                            .filter(|x| !old_target.prerequisites.contains(x))
+                                            .cloned()
+                                            .collect::<Vec<_>>();
+                                        old_target.prerequisites.extend(new_prerequisites);
+                                    }
+                                    _ => {
+                                        let new_target = Target {
+                                            name: target.clone(),
+                                            prerequisites: prerequisites.clone(),
+                                            commands: commands.clone(),
+                                            already_updated: Cell::new(false),
+                                        };
+                                        targets.insert(target.clone(), Rc::new(RefCell::new(new_target)));
+                                    }
                                 }
                             }
                         }
                     },
                     LineType::Macro => {
-                        let (name, value) = line_tokens.split_once('=').unwrap();
-                        let name = self.expand_macros(&name);
-                        match self.macros.get(&name) {
+                        let (name, mut value) = line_tokens.split_once('=').unwrap();
+                        let name = self.expand_macros(&name, None);
+                        // GNUisms are annoying, but popular
+                        let mut expand_value = false;
+                        let mut skip_if_defined = false;
+                        let mut append = false;
+                        let name = if let Some(real_name) = name.strip_suffix("::") {
+                            expand_value = true;
+                            real_name
+                        } else if let Some(real_name) = name.strip_suffix(":") {
+                            expand_value = true;
+                            real_name
+                        } else if let Some(real_name) = name.strip_suffix("?") {
+                            skip_if_defined = true;
+                            real_name
+                        } else if let Some(real_name) = name.strip_suffix("+") {
+                            append = true;
+                            real_name
+                        } else {
+                            &name
+                        };
+
+                        let name = name.trim_end();
+                        value.trim_start();
+
+                        let value = if expand_value {
+                            TokenString::text(self.expand_macros(&value, None))
+                        } else {
+                            value
+                        };
+
+                        match self.macros.get(name) {
                             // We always let command line or MAKEFLAGS macros override macros from the file.
                             Some((MacroSource::CommandLineOrMAKEFLAGS, _)) => continue,
                             // We let environment variables override macros from the file only if the command-line argument to do that was given
                             Some((MacroSource::Environment, _)) if self.args.environment_overrides => continue,
+                            _ if skip_if_defined => continue,
                             _ => {}
                         }
-                        self.macros.insert(name, (MacroSource::File, value));
+
+                        let value = match self.macros.remove(name) {
+                            Some((_, mut old_value)) if append => {
+                                // TODO eagerly expand if appending to eagerly-expanded macro
+                                old_value.extend(TokenString::text(" "));
+                                old_value.extend(value);
+                                old_value
+                            },
+                            _ => value
+                        };
+                        self.macros.insert(name.into(), (MacroSource::File, value));
                     }
                     LineType::Unknown => {
                         panic!("Unknown line {:?}", line_tokens);
@@ -377,57 +510,182 @@ impl Makefile {
         self
     }
 
-    fn get_target(&mut self, name: impl Into<String>) -> &mut Target {
-        let name = name.into();
-        {
-            let rules_get_name = self.rules.get(&name);
-            let make_target = || {
-                if let Some(target_rule) = rules_get_name {
-                    return Target {
-                        name: name.clone(),
-                        prerequisites: target_rule.prerequisites.clone(),
-                        already_updated: false,
-                        rule: Some(target_rule.clone())
+    fn special_target_has_prereq(&self, target: &str, name: &str) -> bool {
+        let targets = self.targets.borrow();
+        match targets.get(target) {
+            Some(target) => {
+                let target = target.borrow();
+                target.prerequisites.len() == 0 || target.prerequisites.contains(&name.into())
+            },
+            None => false,
+        }
+    }
+
+    pub fn get_target(&self, name: &str) -> Rc<RefCell<Target>> {
+        // TODO implement .POSIX
+        let follow_gnu = true;
+
+        let vpath_options = match self.macros.get("VPATH") {
+            Some((_, vpath)) if follow_gnu => {
+                let vpath = self.expand_macros(vpath, None);
+                env::split_paths(&vpath).collect()
+            }
+            _ => vec![]
+        };
+
+        let mut targets = self.targets.borrow_mut();
+        let exists_but_infer_anyway = if follow_gnu {
+            match targets.get(name) {
+                Some(target) => {
+                    let target = target.borrow();
+                    target.commands.is_empty()
+                }
+                None => false,
+            }
+        } else {
+            false
+        };
+        if !targets.contains_key(name) || exists_but_infer_anyway {
+            // When no target rule is found to update a target, the inference rules shall
+            // be checked. The suffix of the target to be built...
+            let suffix = Path::new(name).extension().map_or_else(String::new, |ext| ext.to_string_lossy().into());
+            // is compared to the list of suffixes specified by the .SUFFIXES special
+            // targets. If the .s1 suffix is found in .SUFFIXES...
+            if self.special_target_has_prereq(".SUFFIXES", &suffix) || suffix.is_empty() {
+                // the inference rules shall be searched in the order defined...
+                'rules: for rule in &self.inference_rules {
+                    // for the first .s2.s1 rule...
+                    if rule.product == suffix {
+                        // whose prerequisite file ($*.s2) exists.
+                        let prereq_path = Path::new(name).with_extension(rule.prereq.clone());
+                        let prereq_path_options = if prereq_path.is_absolute() {
+                            vec![prereq_path]
+                        } else {
+                            let mut options = vec![prereq_path.clone()];
+                            options.extend(vpath_options.iter().map(|vpath| vpath.join(&prereq_path)));
+                            options
+                        };
+                        for prereq in prereq_path_options {
+                            if prereq.exists() {
+                                let new_target = Target {
+                                    name: name.into(),
+                                    prerequisites: vec![prereq.to_string_lossy().into()],
+                                    commands: rule.commands.clone(),
+                                    already_updated: Cell::new(false),
+                                };
+                                targets.insert(name.into(), Rc::new(RefCell::new(new_target)));
+                                break 'rules;
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        if !targets.contains_key(name) {
+            // well, inference didn't work. is there a default?
+            if let Some(default) = targets.get(".DEFAULT") {
+                let default = default.borrow();
+                let commands = default.commands.clone();
+                drop(default);
+                let new_target = Target {
+                    name: name.into(),
+                    prerequisites: vec![],
+                    commands,
+                    already_updated: Cell::new(false),
+                };
+                targets.insert(name.into(), Rc::new(RefCell::new(new_target)));
+            } else {
+                // if it already exists, it counts as up-to-date
+                if Path::new(name).exists() {
+                    let new_target = Target {
+                        name: name.into(),
+                        prerequisites: vec![],
+                        commands: vec![],
+                        already_updated: Cell::new(true),
                     };
+                    targets.insert(name.into(), Rc::new(RefCell::new(new_target)));
                 }
-                panic!("uhhhhh i don't even know anymore bro");
-            };
-            self.targets
-                .entry(name.clone())
-                .or_insert_with(make_target);
+            }
         }
-        self.targets.get_mut(&name).unwrap()
+
+        drop(targets);
+        let targets = self.targets.borrow();
+
+        targets.get(name).expect("Target not found!").clone()
     }
 
-    fn update_target(&mut self, name: impl Into<String>) {
-        // This is the dumbest fucking thing I've ever had to do.
-        // We can't leave it in the map, because then we have overlapping mutable borrows of self,
-        // so we have to remove it from the map, do the work, and then re-insert it into the map.
-        // Fuck this so much.
-        // Why the goddamn hell do I even write Rust.
-        let name = name.into();
-        {
-            let _ = self.get_target(name.clone());
-        }
-        let mut target = self.targets.remove(&name).unwrap();
+    pub fn update_target(&self, name: &str) {
+        let target = self.get_target(name);
+        let target = target.borrow();
         target.update(self);
-        self.targets.insert(name.clone(), target);
     }
 
-    fn expand_macros(&self, text: &TokenString) -> String {
+    fn expand_macros(&self, text: &TokenString, target: Option<&Target>) -> String {
         let mut result = String::new();
         for token in text.tokens() {
             match token {
                 Token::Text(t) => result.push_str(t),
                 Token::MacroExpansion { name, replacement } => {
-                    let (_, macro_value) = &self.macros[name];
-                    let macro_value = self.expand_macros(macro_value);
+                    let internal_macro_names = &['@', '?', '<', '*'][..];
+                    let internal_macro_suffices = &['D', 'F'][..];
+                    let just_internal = name.len() == 1 && name.starts_with(internal_macro_names);
+                    let suffixed_internal = name.len() == 2 && name.starts_with(internal_macro_names) && name.ends_with(internal_macro_suffices);
+                    let macro_value = if just_internal || suffixed_internal {
+                        let target = target.expect("internal macro but no current target!");
+                        let macro_pieces = if name.starts_with('@') {
+                            // The $@ shall evaluate to the full target name of the
+                            // current target.
+                            vec![target.name.clone()]
+                        } else if name.starts_with('?') {
+                            // The $? macro shall evaluate to the list of prerequisites
+                            // that are newer than the current target.
+                            target.prerequisites
+                                .iter()
+                                .filter(|prereq| self.get_target(prereq).borrow().newer_than(target).unwrap_or(false))
+                                .cloned()
+                                .collect()
+                        } else if name.starts_with('<') {
+                            // In an inference rule, the $< macro shall evaluate to the
+                            // filename whose existence allowed the inference rule to be
+                            // chosen for the target. In the .DEFAULT rule, the $< macro
+                            // shall evaluate to the current target name.
+                            target.prerequisites.clone()
+                        } else if name.starts_with('*') {
+                            // The $* macro shall evaluate to the current target name with
+                            // its suffix deleted.
+                            vec![Path::new(name).with_extension("").to_string_lossy().into()]
+                        } else {
+                            unreachable!()
+                        };
+
+                        let macro_pieces = if name.ends_with('D') {
+                            macro_pieces.into_iter()
+                                .map(|x| Path::new(&x).parent().expect("no parent").to_string_lossy().into())
+                                .collect()
+                        } else if name.ends_with('F') {
+                            macro_pieces.into_iter()
+                                .map(|x| Path::new(&x).file_name().expect("no filename").to_string_lossy().into())
+                                .collect()
+                        } else {
+                            macro_pieces
+                        };
+
+                        macro_pieces.join(" ")
+                    } else {
+                        match self.macros.get(name) {
+                            Some((_, macro_value)) => self.expand_macros(&macro_value, target),
+                            None => {
+                                String::new()
+                            }
+                        }
+                    };
                     let macro_value = match replacement {
                         Some((subst1, subst2)) => {
-                            let subst1 = self.expand_macros(subst1);
+                            let subst1 = self.expand_macros(subst1, target);
                             let subst1_suffix = regex::escape(&subst1);
                             let subst1_suffix = Regex::new(&format!(r"{}\b", subst1_suffix)).unwrap();
-                            let subst2 = self.expand_macros(subst2);
+                            let subst2 = self.expand_macros(subst2, target);
                             subst1_suffix.replace_all(&macro_value, subst2).to_string()
                         },
                         None => macro_value,
@@ -440,5 +698,40 @@ impl Makefile {
     }
 }
 
-const BUILTIN_RULES: &'static [(&'static str, Rule)] = &[];
-const BUILTIN_SUFFIX_LIST: &'static [&'static str] = &[];
+impl fmt::Display for Makefile {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let header = |f: &mut fmt::Formatter, t: &str| {
+            writeln!(f, "{}\n{:=^width$}", t, "", width = t.len())
+        };
+        header(f, "Inference Rules")?;
+        for rule in &self.inference_rules {
+            writeln!(f, "{}", rule)?;
+        }
+        writeln!(f)?;
+
+        header(f, "Macros")?;
+        for (k, (_, v)) in &self.macros {
+            writeln!(f, "{}={}", k, v)?;
+        }
+        writeln!(f)?;
+
+        header(f, "Targets")?;
+        let targets = self.targets.borrow();
+        for (_, target) in &*targets {
+            let target = target.borrow();
+            writeln!(f, "{}", target)?;
+        }
+
+        Ok(())
+    }
+}
+
+fn builtin_inference_rules() -> Vec<InferenceRule> {
+    todo!()
+}
+fn builtin_macros() -> Vec<(&'static str, TokenString)> {
+    todo!()
+}
+fn builtin_targets() -> Vec<Target> {
+    todo!()
+}
diff --git a/src/makefile/token.rs b/src/makefile/token.rs
index 3f69b50..4943010 100644
--- a/src/makefile/token.rs
+++ b/src/makefile/token.rs
@@ -1,3 +1,4 @@
+use std::fmt;
 use std::str::FromStr;
 
 use nom::{
@@ -14,6 +15,10 @@ use nom::{
 pub struct TokenString(Vec<Token>);
 
 impl TokenString {
+    pub fn text(text: impl Into<String>) -> Self {
+        Self(vec![Token::Text(text.into())])
+    }
+
     pub fn tokens(&self) -> impl Iterator<Item=&Token> {
         self.0.iter()
     }
@@ -41,6 +46,40 @@ impl TokenString {
         }
         None
     }
+
+    pub fn ends_with(&self, pattern: &str) -> bool {
+        match self.0.last() {
+            Some(Token::Text(t)) => t.ends_with(pattern),
+            _ => false
+        }
+    }
+
+    pub fn strip_suffix(&mut self, suffix: &str) {
+        if let Some(Token::Text(t)) = self.0.last_mut() {
+            if let Some(x) = t.strip_suffix(suffix) {
+                *t = x.into()
+            }
+        }
+    }
+
+    pub fn extend(&mut self, other: TokenString) {
+        self.0.extend(other.0);
+    }
+
+    pub fn trim_start(&mut self) {
+        if let Some(Token::Text(t)) = self.0.last_mut() {
+            *t = t.trim_start().into();
+        }
+    }
+}
+
+impl fmt::Display for TokenString {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        for t in &self.0 {
+            write!(f, "{}", t)?;
+        }
+        Ok(())
+    }
 }
 
 #[derive(PartialEq, Eq, Clone, Debug)]
@@ -52,6 +91,16 @@ pub enum Token {
     },
 }
 
+impl fmt::Display for Token {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Token::Text(t) => write!(f, "{}", t),
+            Token::MacroExpansion { name, replacement: None } => write!(f, "$({})", name),
+            Token::MacroExpansion { name, replacement: Some((r1, r2)) } => write!(f, "$({}:{}={})", name, r1, r2),
+        }
+    }
+}
+
 fn macro_name(input: &str) -> IResult<&str, &str> {
     // POSIX says "periods, underscores, digits, and alphabetics from the portable character set"
     take_while1(|c: char| {