feat(build): add flat-bin kind and FAT [archive] packing for OS-dev

src/core/build/builder/artifact.rs

@@ -19,9 +19,130 @@ use crate::core::build::builder::BuildContext;
 use crate::core::build::common;
 use crate::platform;
 use crate::utils::build::is_bare_metal_target;
+use std::path::{Path, PathBuf};
 use std::process::Command;
 use std::time::Instant;
 
+pub(crate) fn artifact_dir(ctx: &BuildContext) -> PathBuf {
+    match ctx.target_dir {
+        Some(dir) => Path::new(dir).to_path_buf(),
+        None => Path::new("./target").join(ctx.profile),
+    }
+}
+
+pub(crate) fn flat_output_path(ctx: &BuildContext) -> String {
+    let name = ctx.output_filename.unwrap_or(ctx.project_name);
+    let ext = ctx.output_extension.unwrap_or("bin");
+    let file = if ext.is_empty() {
+        name.to_string()
+    } else {
+        format!("{name}.{ext}")
+    };
+    artifact_dir(ctx).join(file).to_string_lossy().to_string()
+}
+
+pub(crate) fn flat_source_output_path(ctx: &BuildContext, source: &str) -> String {
+    let stem = Path::new(source)
+        .file_stem()
+        .and_then(|s| s.to_str())
+        .unwrap_or("out");
+    let ext = ctx.output_extension.unwrap_or("bin");
+    let file = if ext.is_empty() {
+        stem.to_string()
+    } else {
+        format!("{stem}.{ext}")
+    };
+    artifact_dir(ctx).join(file).to_string_lossy().to_string()
+}
+
+fn resolve_objcopy() -> Result<String, String> {
+    for candidate in ["llvm-objcopy", "objcopy", "gobjcopy"] {
+        if Command::new(candidate)
+            .arg("--version")
+            .output()
+            .map(|o| o.status.success())
+            .unwrap_or(false)
+        {
+            return Ok(candidate.to_string());
+        }
+    }
+    Err(
+        "flat-bin requires llvm-objcopy, objcopy, or gobjcopy in PATH \
+         (install binutils or LLVM tools)"
+            .to_string(),
+    )
+}
+
+pub(crate) fn objcopy_binary(ctx: &BuildContext, input: &str, output: &str) -> Result<(), String> {
+    if let Some(parent) = Path::new(output).parent() {
+        std::fs::create_dir_all(parent).map_err(|e| format!("output dir error: {e}"))?;
+    }
+    if !common::needs_rebuild(input, output) {
+        return Ok(());
+    }
+    let tool = resolve_objcopy()?;
+    let mut cmd = Command::new(&tool);
+    cmd.arg("-O").arg("binary").arg(input).arg(output);
+    if ctx.verbose || std::env::var("DCR_DEBUG").is_ok() {
+        eprintln!("[dcr] {:?}", cmd);
+    }
+    common::run_command_sync_output(&mut cmd)
+}
+
+pub(crate) fn link_flat_binary(
+    ctx: &BuildContext,
+    objects: &[String],
+    default_linker: &str,
+    start_time: Instant,
+) -> Result<f64, String> {
+    let out_path = flat_output_path(ctx);
+    if !common::needs_link(objects, &out_path) {
+        return Ok(common::elapsed_secs(start_time));
+    }
+
+    let intermediate = {
+        let dir = match ctx.target_dir {
+            Some(dir) => Path::new(dir).join("obj"),
+            None => Path::new("./target").join(ctx.profile).join("obj"),
+        };
+        std::fs::create_dir_all(&dir).map_err(|e| format!("obj dir error: {e}"))?;
+        dir.join(format!("{}.flat.elf", ctx.project_name))
+            .to_string_lossy()
+            .to_string()
+    };
+
+    let mut cmd = Command::new(ctx.linker.unwrap_or(default_linker));
+    cmd.arg("-nostdlib").arg("-static");
+    for obj in objects {
+        cmd.arg(obj);
+    }
+    for dir in ctx.lib_dirs {
+        cmd.arg(format!("-L{dir}"));
+    }
+    for lib in ctx.libs {
+        cmd.arg(format!("-l{lib}"));
+    }
+    for flag in ctx.ldflags {
+        cmd.arg(flag);
+    }
+    cmd.arg("-o").arg(&intermediate);
+
+    if ctx.verbose || std::env::var("DCR_DEBUG").is_ok() {
+        eprintln!("[dcr] {:?}", cmd);
+    }
+    let output = cmd.output().map_err(|err| format!("Build failed: {err}"))?;
+    if !output.status.success() {
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        let stdout = String::from_utf8_lossy(&output.stdout);
+        return Err(format!(
+            "flat-bin link failed:\nstdout: {stdout}\nstderr: {stderr}"
+        ));
+    }
+
+    objcopy_binary(ctx, &intermediate, &out_path)?;
+    Ok(common::elapsed_secs(start_time))
+}
+
 pub(crate) fn archive_static(
     ctx: &BuildContext,
     objects: &[String],
@@ -56,6 +177,10 @@ pub(crate) fn link_binary(
     default_linker: &str,
     start_time: Instant,
 ) -> Result<f64, String> {
+    if crate::utils::build::is_flat_bin(ctx.kind) {
+        return link_flat_binary(ctx, objects, default_linker, start_time);
+    }
+
     let mut cmd = Command::new(ctx.linker.unwrap_or(default_linker));
     if ctx.kind == "sharedlib" {
         if cfg!(target_os = "macos") {