Add support to specify the entrypoint

Closes #54

CHANGELOG.md

@@ -27,6 +27,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Add way to define a non hardcoded `_gp` symbol for a given segment.
   - Used by defining the `gp_info` field on a segment.
   - Can't be combined with the global `hardcoded_gp_value`.
+- Add new top-level attribute for the file format: `entry`.
+  - Specifies the entrypoint for the build.
 
 ### Changed
 

docs/file_format/README.md

@@ -6,6 +6,19 @@ attribute. Other optional top-level attributes may be specified, like
 [vram_classes](vram_classes.md) or [symbol_assignments](symbol_assignments.md).
 Check their specific documents for in-deep explanations.
 
+## Format itself
+
+The document is composed by the following top-level attributes:
+
+- [`settings`](settings.md).
+- A list of [`vram_classes`](vram_classes.md).
+- A list of [`segments`](segments.md).
+  - This list is required.
+- `entry`
+  - A single optional string that specifies the entrypoint of the final build.
+- A list of [`symbol_assignments`](symbol_assignments.md).
+- A list of [`required_symbols`](required_symbols.md).
+
 ## Example
 
 The following example corresponds to the

slinky/src/document.rs

@@ -20,6 +20,7 @@ pub struct Document {
 
     pub segments: Vec<Segment>,
 
+    pub entry: Option<String>,
     pub symbol_assignments: Vec<SymbolAssignment>,
     pub required_symbols: Vec<RequiredSymbol>,
 }
@@ -59,6 +60,8 @@ pub(crate) struct DocumentSerial {
 
     pub segments: Vec<SegmentSerial>,
 
+    #[serde(default)]
+    pub entry: AbsentNullable<String>,
     #[serde(default)]
     pub symbol_assignments: AbsentNullable<Vec<SymbolAssignmentSerial>>,
     #[serde(default)]
@@ -85,6 +88,8 @@ impl DocumentSerial {
 
         let segments = self.segments.unserialize(&settings)?;
 
+        let entry = self.entry.get_non_null_no_default("entry")?;
+
         let symbol_assignments = self
             .symbol_assignments
             .get_non_null("symbol_assignments", Vec::new)?
@@ -99,6 +104,7 @@ impl DocumentSerial {
             settings,
             vram_classes,
             segments,
+            entry,
             symbol_assignments,
             required_symbols,
         })

slinky/src/linker_writer.rs

@@ -94,6 +94,16 @@ impl ScriptImporter for LinkerWriter<'_> {
         Ok(())
     }
 
+    fn add_entry(&mut self, entry: &str) -> Result<(), SlinkyError> {
+        if !self.buffer.is_empty() {
+            self.buffer.write_empty_line();
+        }
+
+        self.buffer.writeln(&format!("ENTRY({});", entry));
+
+        Ok(())
+    }
+
     fn add_all_symbol_assignments(
         &mut self,
         symbol_assignments: &[SymbolAssignment],

slinky/src/partial_linker_writer.rs

@@ -75,6 +75,10 @@ impl ScriptImporter for PartialLinkerWriter<'_> {
         Ok(())
     }
 
+    fn add_entry(&mut self, entry: &str) -> Result<(), SlinkyError> {
+        self.main_writer.add_entry(entry)
+    }
+
     fn add_all_symbol_assignments(
         &mut self,
         symbol_assignments: &[SymbolAssignment],

slinky/src/traits.rs

@@ -30,6 +30,7 @@ mod private {
 
 pub trait ScriptImporter: private::Sealed {
     fn add_all_segments(&mut self, segments: &[Segment]) -> Result<(), SlinkyError>;
+    fn add_entry(&mut self, entry: &str) -> Result<(), SlinkyError>;
     fn add_all_symbol_assignments(
         &mut self,
         symbol_assignments: &[SymbolAssignment],
@@ -41,6 +42,9 @@ pub trait ScriptImporter: private::Sealed {
 
     fn add_whole_document(&mut self, document: &Document) -> Result<(), SlinkyError> {
         self.add_all_segments(&document.segments)?;
+        if let Some(entry) = &document.entry {
+            self.add_entry(entry)?;
+        }
         self.add_all_symbol_assignments(&document.symbol_assignments)?;
         self.add_all_required_symbols(&document.required_symbols)?;
 

tests/partial_linking/follow_segment.ld

@@ -346,3 +346,5 @@ SECTIONS
         *(*);
     }
 }
+
+ENTRY(ENTRYPOINT);

tests/partial_linking/follow_segment.yaml

@@ -43,3 +43,5 @@ segments:
       - { path: src/main/main.o }
       - { path: src/main/dmadata.o }
       - { path: asm/main/util.o }
+
+entry: ENTRYPOINT

tests/test_cases/drmario64.ld

@@ -8093,3 +8093,5 @@ SECTIONS
         *(*);
     }
 }
+
+ENTRY(entrypoint);

tests/test_cases/drmario64.yaml

@@ -781,3 +781,5 @@ segments:
     fixed_vram: 0x0
     files:
       - { path: src/assets/tutorial/tutorial_kasa.o }
+
+entry: entrypoint