Merge pull request #57 from NotAShelf/notashelf/push-pynzzylozqql

NO MORE STDS!!!!!

.cargo/config.toml

@@ -1,3 +1,16 @@
-# https://github.com/rui314/mold?tab=readme-ov-file#how-to-use
+# Use a linker wrapper that invokes mold then strips junk sections with objcopy.
+# mold cannot discard .eh_frame/.dynstr/.comment via linker scripts, so we do
+# it as a post-link step.
+# See:
+#  <https://github.com/rui314/mold?tab=readme-ov-file#how-to-use>
+#
+# Binary-specific link flags live in microfetch/build.rs via cargo:rustc-link-arg-bin
+# so they only affect the final binary and don't break proc-macro or build-script linking.
 [target.'cfg(target_os = "linux")']
-rustflags = [ "-C", "link-arg=-fuse-ld=mold" ]
+linker = "scripts/ld-wrapper"
+rustflags = [
+  # Suppress .eh_frame emission from our own codegen (does not cover compiler_builtins;
+  # those remnants are removed by the linker wrapper via objcopy post-link)
+  "-C",
+  "force-unwind-tables=no",
+]

.github/workflows/hotpath-profile.yml

@@ -16,6 +16,11 @@ jobs:
           fetch-depth: 0
 
       - uses: actions-rust-lang/setup-rust-toolchain@v1
+        with:
+          rustflags: ""
+
+      - name: Make Mold the default linker
+        uses: rui314/setup-mold@v1
 
       - name: Create metrics directory
         run: mkdir -p /tmp/metrics

.github/workflows/rust.yml

@@ -29,16 +29,18 @@ jobs:
       uses: actions-rust-lang/setup-rust-toolchain@v1
       with:
         target: ${{ matrix.target }}
+        rustflags: ""
 
     - name: "Make Mold the default linker"
       uses: rui314/setup-mold@v1
 
-    - name: "Install cross"
-      run: cargo install cross --git https://github.com/cross-rs/cross
+    - name: "Setup cross-compilation toolchain"
+      uses: taiki-e/setup-cross-toolchain-action@v1
+      with:
+        target: ${{ matrix.target }}
 
     - name: "Build"
-      run: cross build --verbose --target ${{ matrix.target }}
+      run: cargo build --verbose
 
     - name: "Run tests"
-      if: matrix.target == 'x86_64-unknown-linux-gnu'
-      run: cross test --verbose --target ${{ matrix.target }}
+      run: cargo test --workspace --exclude microfetch --verbose

Cargo.lock

@@ -582,9 +582,15 @@ name = "microfetch"
 version = "0.4.13"
 dependencies = [
  "hotpath",
+ "microfetch-alloc",
+ "microfetch-asm",
  "microfetch-lib",
 ]
 
+[[package]]
+name = "microfetch-alloc"
+version = "0.4.13"
+
 [[package]]
 name = "microfetch-asm"
 version = "0.4.13"

Cargo.toml

@@ -10,6 +10,7 @@ rust-version = "1.92.0"
 version      = "0.4.13"
 
 [workspace.dependencies]
+microfetch-alloc = { path = "./crates/alloc" }
 microfetch-asm   = { path = "./crates/asm" }
 microfetch-lib   = { path = "./crates/lib" }
 
@@ -18,6 +19,7 @@ criterion-cycles-per-byte = "0.8.0"
 
 [profile.dev]
 opt-level = 1
+panic     = "abort"
 
 [profile.release]
 codegen-units = 1

crates/alloc/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name                   = "microfetch-alloc"
+description            = "Simple, std-free bump allocator for Microfetch"
+version.workspace      = true
+edition.workspace      = true
+authors.workspace      = true
+rust-version.workspace = true
+license.workspace      = true
+publish                = false
+
+[lints]
+workspace = true

crates/alloc/src/lib.rs

@@ -0,0 +1,106 @@
+//! Simple bump allocator for `no_std` environments. Uses a statically allocated
+//! 32KB buffer and provides O(1) allocation with no deallocation support
+//! (memory is never freed).
+#![no_std]
+use core::{
+  alloc::{GlobalAlloc, Layout},
+  cell::UnsafeCell,
+  ptr::null_mut,
+};
+
+/// Default heap size is 32KB, should be plenty for Microfetch. Technically it
+/// can be invoked with more (or less) depending on our needs but I am quite
+/// sure 32KB is more than enough.
+pub const DEFAULT_HEAP_SIZE: usize = 32 * 1024;
+
+/// A simple bump allocator that never frees memory.
+///
+/// This allocator maintains a static buffer and a bump pointer. Allocations are
+/// fast (just bump the pointer), but memory is never reclaimed. While you might
+/// be inclined to point out that this is ugly, it's suitable for a short-lived
+/// program with bounded memory usage.
+pub struct BumpAllocator<const N: usize = DEFAULT_HEAP_SIZE> {
+  heap: UnsafeCell<[u8; N]>,
+  next: UnsafeCell<usize>,
+}
+
+// SAFETY: BumpAllocator is thread-safe because it uses UnsafeCell
+// and the allocator is only used in single-threaded contexts (i.e., no_std).
+unsafe impl<const N: usize> Sync for BumpAllocator<N> {}
+
+impl<const N: usize> BumpAllocator<N> {
+  /// Creates a new bump allocator with the specified heap size.
+  #[must_use]
+  pub const fn new() -> Self {
+    Self {
+      heap: UnsafeCell::new([0; N]),
+      next: UnsafeCell::new(0),
+    }
+  }
+
+  /// Returns the number of bytes currently allocated.
+  #[must_use]
+  pub fn used(&self) -> usize {
+    // SAFETY: We're just reading the value, and this is only called
+    // in single-threaded contexts.
+    unsafe { *self.next.get() }
+  }
+
+  /// Returns the total heap size.
+  #[must_use]
+  pub const fn capacity(&self) -> usize {
+    N
+  }
+
+  /// Returns the number of bytes remaining.
+  #[must_use]
+  pub fn remaining(&self) -> usize {
+    N - self.used()
+  }
+}
+
+impl<const N: usize> Default for BumpAllocator<N> {
+  fn default() -> Self {
+    Self::new()
+  }
+}
+
+unsafe impl<const N: usize> GlobalAlloc for BumpAllocator<N> {
+  unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+    unsafe {
+      let next = self.next.get();
+      let heap = self.heap.get();
+
+      // Align the current position
+      let align = layout.align();
+      let start = (*next + align - 1) & !(align - 1);
+      let end = start + layout.size();
+
+      if end > N {
+        // Out of memory
+        null_mut()
+      } else {
+        *next = end;
+        (*heap).as_mut_ptr().add(start)
+      }
+    }
+  }
+
+  unsafe fn dealloc(&self, _ptr: *mut u8, _layout: Layout) {
+    // Bump allocator doesn't support deallocation
+    // Memory is reclaimed when the program exits
+  }
+}
+
+/// Static bump allocator instance with 32KB heap.
+///
+/// # Example
+///
+/// Use this with `#[global_allocator]` in your binary:
+///
+///
+/// ```rust,ignore
+/// #[global_allocator]
+/// static ALLOCATOR: BumpAllocator = BumpAllocator::new();
+/// ```
+pub type BumpAlloc = BumpAllocator<DEFAULT_HEAP_SIZE>;

crates/asm/src/lib.rs

@@ -19,6 +19,137 @@ compile_error!(
   "Unsupported architecture: only x86_64, aarch64, and riscv64 are supported"
 );
 
+/// Copies `n` bytes from `src` to `dest`.
+///
+/// # Safety
+///
+/// `dest` and `src` must be valid pointers to non-overlapping regions of
+/// memory of at least `n` bytes.
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn memcpy(
+  dest: *mut u8,
+  src: *const u8,
+  n: usize,
+) -> *mut u8 {
+  for i in 0..n {
+    unsafe {
+      *dest.add(i) = *src.add(i);
+    }
+  }
+  dest
+}
+
+/// Fills memory region with a byte value.
+///
+/// # Safety
+///
+/// `s` must be a valid pointer to memory of at least `n` bytes.
+/// The value in `c` is treated as unsigned (lower 8 bits used).
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn memset(s: *mut u8, c: i32, n: usize) -> *mut u8 {
+  for i in 0..n {
+    unsafe {
+      *s.add(i) = u8::try_from(c).unwrap_or(0);
+    }
+  }
+  s
+}
+
+/// Compares two byte sequences.
+///
+/// # Safety
+///
+/// `s1` and `s2` must be valid pointers to memory of at least `n` bytes.
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn bcmp(s1: *const u8, s2: *const u8, n: usize) -> i32 {
+  for i in 0..n {
+    let a = unsafe { *s1.add(i) };
+    let b = unsafe { *s2.add(i) };
+    if a != b {
+      return i32::from(a) - i32::from(b);
+    }
+  }
+  0
+}
+
+/// Compares two byte sequences.
+///
+/// # Safety
+///
+/// `s1` and `s2` must be valid pointers to memory of at least `n` bytes.
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32 {
+  unsafe { bcmp(s1, s2, n) }
+}
+
+/// Calculates the length of a null-terminated string.
+///
+/// # Safety
+///
+/// `s` must be a valid pointer to a null-terminated string.
+#[unsafe(no_mangle)]
+pub const unsafe extern "C" fn strlen(s: *const u8) -> usize {
+  let mut len = 0;
+  while unsafe { *s.add(len) } != 0 {
+    len += 1;
+  }
+  len
+}
+
+/// Function pointer type for the main application entry point.
+/// The function receives argc and argv and should return an exit code.
+#[cfg(not(test))]
+pub type MainFn = unsafe extern "C" fn(i32, *const *const u8) -> i32;
+
+#[cfg(not(test))]
+static mut MAIN_FN: Option<MainFn> = None;
+
+/// Register the main function to be called from the entry point.
+/// This must be called before the program starts (e.g., in a constructor).
+#[cfg(not(test))]
+pub fn register_main(main_fn: MainFn) {
+  unsafe {
+    MAIN_FN = Some(main_fn);
+  }
+}
+
+/// Rust entry point called from `_start` assembly.
+///
+/// The `stack` pointer points to:
+/// `[rsp]`     = argc
+/// `[rsp+8]`   = argv[0]
+/// etc.
+///
+/// # Safety
+///
+/// The `stack` pointer must point to valid stack memory set up by the kernel
+/// AND the binary must define a `main` function with the following signature:
+///
+/// ```rust,ignore
+/// unsafe extern "C" fn main(argc: i32, argv: *const *const u8) -> i32`
+/// ```
+#[cfg(not(test))]
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn entry_rust(stack: *const usize) -> i32 {
+  // Read argc and argv from stack
+  let argc = unsafe { *stack };
+  let argv = unsafe { stack.add(1).cast::<*const u8>() };
+
+  // SAFETY: argc is unlikely to exceed i32::MAX on real systems
+  let argc_i32 = i32::try_from(argc).unwrap_or(i32::MAX);
+
+  // Call the main function (defined by the binary crate)
+  unsafe { main(argc_i32, argv) }
+}
+
+// External main function that must be defined by the binary using this crate.
+// Signature: `unsafe extern "C" fn main(argc: i32, argv: *const *const u8) ->
+// i32`
+#[cfg(not(test))]
+unsafe extern "C" {
+  fn main(argc: i32, argv: *const *const u8) -> i32;
+}
+
 /// Direct syscall to open a file
 ///
 /// # Returns
@@ -507,6 +638,7 @@ pub fn read_file_fast(path: &str, buffer: &mut [u8]) -> Result<usize, i32> {
     let _ = sys_close(fd);
 
     if bytes_read < 0 {
+      #[allow(clippy::cast_possible_truncation)]
       return Err(bytes_read as i32);
     }
 
@@ -598,3 +730,41 @@ pub unsafe fn sys_sysinfo(info: *mut SysInfo) -> i64 {
     ret
   }
 }
+
+/// Direct syscall to exit the process
+///
+/// # Safety
+///
+/// This syscall never returns. The process will terminate immediately.
+#[inline]
+pub unsafe fn sys_exit(code: i32) -> ! {
+  #[cfg(target_arch = "x86_64")]
+  unsafe {
+    core::arch::asm!(
+      "syscall",
+      in("rax") 60i64,  // SYS_exit
+      in("rdi") code,
+      options(noreturn, nostack)
+    );
+  }
+
+  #[cfg(target_arch = "aarch64")]
+  unsafe {
+    core::arch::asm!(
+      "svc #0",
+      in("x8") 93i64,  // SYS_exit
+      in("x0") code,
+      options(noreturn, nostack)
+    );
+  }
+
+  #[cfg(target_arch = "riscv64")]
+  unsafe {
+    core::arch::asm!(
+      "ecall",
+      in("a7") 93i64,  // SYS_exit
+      in("a0") code,
+      options(noreturn, nostack)
+    );
+  }
+}

crates/lib/src/colors.rs

@@ -1,5 +1,6 @@
-use std::sync::LazyLock;
+use alloc::string::String;
 
+/// Color codes for terminal output
 pub struct Colors {
   pub reset:   &'static str,
   pub blue:    &'static str,
@@ -11,7 +12,8 @@ pub struct Colors {
 }
 
 impl Colors {
-  const fn new(is_no_color: bool) -> Self {
+  #[must_use]
+  pub const fn new(is_no_color: bool) -> Self {
     if is_no_color {
       Self {
         reset:   "",
@@ -36,46 +38,68 @@ impl Colors {
   }
 }
 
-pub static COLORS: LazyLock<Colors> = LazyLock::new(|| {
+use core::sync::atomic::{AtomicBool, Ordering};
+
+// Check if NO_COLOR is set (only once, lazily)
 // Only presence matters; value is irrelevant per the NO_COLOR spec
-  let is_no_color = std::env::var_os("NO_COLOR").is_some();
-  Colors::new(is_no_color)
-});
+static NO_COLOR_CHECKED: AtomicBool = AtomicBool::new(false);
+static NO_COLOR_SET: AtomicBool = AtomicBool::new(false);
+
+/// Checks if `NO_COLOR` environment variable is set.
+pub(crate) fn is_no_color() -> bool {
+  // Fast path: already checked
+  if NO_COLOR_CHECKED.load(Ordering::Acquire) {
+    return NO_COLOR_SET.load(Ordering::Relaxed);
+  }
+
+  // Slow path: check environment
+  let is_set = crate::env_exists("NO_COLOR");
+  NO_COLOR_SET.store(is_set, Ordering::Relaxed);
+  NO_COLOR_CHECKED.store(true, Ordering::Release);
+  is_set
+}
 
 #[must_use]
 #[cfg_attr(feature = "hotpath", hotpath::measure)]
 pub fn print_dots() -> String {
-  // Pre-calculate capacity: 6 color codes + "  " (glyph + 2 spaces) per color
   const GLYPH: &str = "";
-  let capacity = COLORS.blue.len()
-    + COLORS.cyan.len()
-    + COLORS.green.len()
-    + COLORS.yellow.len()
-    + COLORS.red.len()
-    + COLORS.magenta.len()
-    + COLORS.reset.len()
+
+  let colors = if is_no_color() {
+    Colors::new(true)
+  } else {
+    Colors::new(false)
+  };
+
+  // Pre-calculate capacity: 6 color codes + "  " (glyph + 2 spaces) per color
+  let capacity = colors.blue.len()
+    + colors.cyan.len()
+    + colors.green.len()
+    + colors.yellow.len()
+    + colors.red.len()
+    + colors.magenta.len()
+    + colors.reset.len()
     + (GLYPH.len() + 2) * 6;
 
   let mut result = String::with_capacity(capacity);
-  result.push_str(COLORS.blue);
+  result.push_str(colors.blue);
   result.push_str(GLYPH);
   result.push_str("  ");
-  result.push_str(COLORS.cyan);
+  result.push_str(colors.cyan);
   result.push_str(GLYPH);
   result.push_str("  ");
-  result.push_str(COLORS.green);
+  result.push_str(colors.green);
   result.push_str(GLYPH);
   result.push_str("  ");
-  result.push_str(COLORS.yellow);
+  result.push_str(colors.yellow);
   result.push_str(GLYPH);
   result.push_str("  ");
-  result.push_str(COLORS.red);
+  result.push_str(colors.red);
   result.push_str(GLYPH);
   result.push_str("  ");
-  result.push_str(COLORS.magenta);
+  result.push_str(colors.magenta);
   result.push_str(GLYPH);
   result.push_str("  ");
-  result.push_str(COLORS.reset);
+  result.push_str(colors.reset);
 
   result
 }

crates/lib/src/desktop.rs

@@ -1,18 +1,15 @@
-use std::{ffi::OsStr, fmt::Write};
+use alloc::string::String;
+
+use crate::getenv_str;
 
 #[must_use]
 #[cfg_attr(feature = "hotpath", hotpath::measure)]
 pub fn get_desktop_info() -> String {
-  let desktop_os = std::env::var_os("XDG_CURRENT_DESKTOP");
-  let session_os = std::env::var_os("XDG_SESSION_TYPE");
+  let desktop_raw = getenv_str("XDG_CURRENT_DESKTOP").unwrap_or("Unknown");
+  let session_raw = getenv_str("XDG_SESSION_TYPE").unwrap_or("");
 
-  let desktop_raw = desktop_os
-    .as_deref()
-    .and_then(OsStr::to_str)
-    .unwrap_or("Unknown");
   let desktop_str = desktop_raw.strip_prefix("none+").unwrap_or(desktop_raw);
 
-  let session_raw = session_os.as_deref().and_then(OsStr::to_str).unwrap_or("");
   let backend_str = if session_raw.is_empty() {
     "Unknown"
   } else {
@@ -27,9 +24,15 @@ pub fn get_desktop_info() -> String {
   result.push_str(" (");
 
   // Capitalize first character of backend
-  if let Some(first_char) = backend_str.chars().next() {
-    let _ = write!(result, "{}", first_char.to_ascii_uppercase());
-    result.push_str(&backend_str[first_char.len_utf8()..]);
+  if let Some(first_byte) = backend_str.as_bytes().first() {
+    // Convert first byte to uppercase if it's ASCII lowercase
+    let upper = if first_byte.is_ascii_lowercase() {
+      (first_byte - b'a' + b'A') as char
+    } else {
+      *first_byte as char
+    };
+    result.push(upper);
+    result.push_str(&backend_str[1..]);
   }
 
   result.push(')');

crates/lib/src/lib.rs

@@ -1,13 +1,17 @@
+#![no_std]
+extern crate alloc;
+
 pub mod colors;
 pub mod desktop;
 pub mod release;
 pub mod system;
 pub mod uptime;
 
-use std::{
+use alloc::string::String;
+use core::{
   ffi::CStr,
-  io::{self, Cursor, Write},
   mem::MaybeUninit,
+  sync::atomic::{AtomicPtr, Ordering},
 };
 
 pub use microfetch_asm as syscall;
@@ -25,6 +29,212 @@ pub use microfetch_asm::{
   sys_write,
 };
 
+/// A simple error type for microfetch operations.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Error {
+  /// An OS error occurred, containing the errno value.
+  OsError(i32),
+  /// Invalid data or encoding error.
+  InvalidData,
+  /// Not found.
+  NotFound,
+  /// Write operation failed or partial write.
+  WriteError,
+}
+
+impl Error {
+  /// Creates an error from the last OS error (reads errno).
+  #[inline]
+  #[must_use]
+  pub const fn last_os_error() -> Self {
+    // This is a simplified version - in a real implementation,
+    // we'd need to get the actual errno from the syscall return
+    Self::OsError(0)
+  }
+
+  /// Creates an error from a raw OS error code (negative errno from syscall).
+  #[inline]
+  #[must_use]
+  pub const fn from_raw_os_error(errno: i32) -> Self {
+    Self::OsError(-errno)
+  }
+}
+
+impl core::fmt::Display for Error {
+  fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+    match self {
+      Self::OsError(errno) => write!(f, "OS error: {errno}"),
+      Self::InvalidData => write!(f, "Invalid data"),
+      Self::NotFound => write!(f, "Not found"),
+      Self::WriteError => write!(f, "Write error"),
+    }
+  }
+}
+
+// Simple OnceLock implementation for no_std
+pub struct OnceLock<T> {
+  ptr: AtomicPtr<T>,
+}
+
+impl<T> Default for OnceLock<T> {
+  fn default() -> Self {
+    Self::new()
+  }
+}
+
+impl<T> OnceLock<T> {
+  #[must_use]
+  pub const fn new() -> Self {
+    Self {
+      ptr: AtomicPtr::new(core::ptr::null_mut()),
+    }
+  }
+
+  pub fn get_or_init<F>(&self, f: F) -> &T
+  where
+    F: FnOnce() -> T,
+  {
+    // Load the current pointer
+    let mut ptr = self.ptr.load(Ordering::Acquire);
+
+    if ptr.is_null() {
+      // Need to initialize
+      let value = f();
+      let boxed = alloc::boxed::Box::new(value);
+      let new_ptr = alloc::boxed::Box::into_raw(boxed);
+
+      // Try to set the pointer
+      match self.ptr.compare_exchange(
+        core::ptr::null_mut(),
+        new_ptr,
+        Ordering::Release,
+        Ordering::Acquire,
+      ) {
+        Ok(_) => {
+          // We successfully set it
+          ptr = new_ptr;
+        },
+        Err(existing) => {
+          // Someone else set it first, free our allocation
+          // SAFETY: We just allocated this and no one else has seen it
+          unsafe {
+            let _ = alloc::boxed::Box::from_raw(new_ptr);
+          }
+          ptr = existing;
+        },
+      }
+    }
+
+    // SAFETY: We know ptr is non-null and points to a valid T
+    unsafe { &*ptr }
+  }
+}
+
+impl<T> Drop for OnceLock<T> {
+  fn drop(&mut self) {
+    let ptr = self.ptr.load(Ordering::Acquire);
+    if !ptr.is_null() {
+      // SAFETY: We know this was allocated via Box::into_raw
+      unsafe {
+        let _ = alloc::boxed::Box::from_raw(ptr);
+      }
+    }
+  }
+}
+
+// Store the environment pointer internally,initialized from `main()`. This
+// helps avoid the libc dependency *completely*.
+static ENVP: AtomicPtr<*const u8> = AtomicPtr::new(core::ptr::null_mut());
+
+/// Initialize the environment pointer. Must be called before any `getenv()`
+/// calls. This is called from `main()` with the calculated `envp`.
+///
+/// # Safety
+///
+/// envp must be a valid null-terminated array of C strings, or null if
+/// no environment is available.
+#[inline]
+pub unsafe fn init_env(envp: *const *const u8) {
+  ENVP.store(envp.cast_mut(), Ordering::Release);
+}
+
+/// Gets the current environment pointer.
+#[inline]
+#[must_use]
+fn get_envp() -> *const *const u8 {
+  ENVP.load(Ordering::Acquire)
+}
+
+/// Gets an environment variable by name without using std or libc by reading
+/// from the environment pointer set by [`init_env`].
+#[must_use]
+pub fn getenv(name: &str) -> Option<&'static [u8]> {
+  let envp = get_envp();
+  if envp.is_null() {
+    return None;
+  }
+
+  let name_bytes = name.as_bytes();
+
+  // Walk through environment variables
+  let mut i = 0;
+  loop {
+    // SAFETY: environ is null-terminated array of pointers
+    let entry = unsafe { *envp.add(i) };
+    if entry.is_null() {
+      break;
+    }
+
+    // Check if this entry starts with our variable name followed by '='
+    let mut matches = true;
+    for (j, &b) in name_bytes.iter().enumerate() {
+      // SAFETY: entry is a valid C string
+      let entry_byte = unsafe { *entry.add(j) };
+      if entry_byte != b {
+        matches = false;
+        break;
+      }
+    }
+
+    if matches {
+      // Check for '=' after the name
+      // SAFETY: entry is a valid C string
+      let eq_byte = unsafe { *entry.add(name_bytes.len()) };
+      if eq_byte == b'=' {
+        // Found it! Calculate the value length
+        let value_start = unsafe { entry.add(name_bytes.len() + 1) };
+        let mut len = 0;
+        loop {
+          // SAFETY: entry is a valid C string
+          let b = unsafe { *value_start.add(len) };
+          if b == 0 {
+            break;
+          }
+          len += 1;
+        }
+        // SAFETY: We calculated the exact length
+        return Some(unsafe { core::slice::from_raw_parts(value_start, len) });
+      }
+    }
+
+    i += 1;
+  }
+
+  None
+}
+
+/// Gets an environment variable as a UTF-8 string.
+#[must_use]
+pub fn getenv_str(name: &str) -> Option<&'static str> {
+  getenv(name).and_then(|bytes| core::str::from_utf8(bytes).ok())
+}
+
+/// Checks if an environment variable exists (regardless of its value).
+#[must_use]
+pub fn env_exists(name: &str) -> bool {
+  getenv(name).is_some()
+}
+
 /// Wrapper for `utsname` with safe accessor methods
 pub struct UtsName(UtsNameBuf);
 
@@ -34,11 +244,12 @@ impl UtsName {
   /// # Errors
   ///
   /// Returns an error if the `uname` syscall fails
-  pub fn uname() -> Result<Self, std::io::Error> {
+  pub fn uname() -> Result<Self, Error> {
     let mut uts = MaybeUninit::uninit();
     if unsafe { sys_uname(uts.as_mut_ptr()) } != 0 {
-      return Err(std::io::Error::last_os_error());
+      return Err(Error::last_os_error());
     }
+
     Ok(Self(unsafe { uts.assume_init() }))
   }
 
@@ -78,10 +289,51 @@ struct Fields {
   colors:         String,
 }
 
+/// Minimal, stack-allocated writer implementing `core::fmt::Write`. Avoids heap
+/// allocation for the output buffer.
+struct StackWriter<'a> {
+  buf: &'a mut [u8],
+  pos: usize,
+}
+
+impl<'a> StackWriter<'a> {
+  #[inline]
+  const fn new(buf: &'a mut [u8]) -> Self {
+    Self { buf, pos: 0 }
+  }
+
+  #[inline]
+  fn written(&self) -> &[u8] {
+    &self.buf[..self.pos]
+  }
+}
+
+impl core::fmt::Write for StackWriter<'_> {
+  #[inline]
+  fn write_str(&mut self, s: &str) -> core::fmt::Result {
+    let bytes = s.as_bytes();
+    let to_write = bytes.len().min(self.buf.len() - self.pos);
+    self.buf[self.pos..self.pos + to_write].copy_from_slice(&bytes[..to_write]);
+    self.pos += to_write;
+    Ok(())
+  }
+}
+
+/// Custom logo art embedded at compile time via the `MICROFETCH_LOGO`
+/// environment variable. Set it to 9 newline-separated lines of ASCII/Unicode
+/// art when building to replace the default NixOS logo:
+///
+///   `MICROFETCH_LOGO="$(cat my_logo.txt)"` cargo build --release
+///
+/// Each line maps to one info row. When unset, the built-in two-tone NixOS
+/// logo is used.
+const CUSTOM_LOGO: &str = match option_env!("MICROFETCH_LOGO") {
+  Some(s) => s,
+  None => "",
+};
+
 #[cfg_attr(feature = "hotpath", hotpath::measure)]
-fn print_system_info(
-  fields: &Fields,
-) -> Result<(), Box<dyn std::error::Error>> {
+fn print_system_info(fields: &Fields) -> Result<(), Error> {
   let Fields {
     user_info,
     os_name,
@@ -94,55 +346,189 @@ fn print_system_info(
     colors,
   } = fields;
 
-  let cyan = colors::COLORS.cyan;
-  let blue = colors::COLORS.blue;
-  let reset = colors::COLORS.reset;
+  let no_color = colors::is_no_color();
+  let c = colors::Colors::new(no_color);
 
   let mut buf = [0u8; 2048];
-  let mut cursor = Cursor::new(&mut buf[..]);
+  let mut w = StackWriter::new(&mut buf);
 
-  write!(
-    cursor,
-    "
-    {blue}     ▟█▖    {cyan}▝█▙ ▗█▛         {user_info} ~{reset}
-    {blue}  ▗▄▄▟██▄▄▄▄▄{cyan}▝█▙█▛  {blue}▖       {cyan}  {blue}System{reset}        {os_name}
-    {blue}  ▀▀▀▀▀▀▀▀▀▀▀▘{cyan}▝██  {blue}▟█▖      {cyan}  {blue}Kernel{reset}        {kernel_version}
-    {cyan}     ▟█▛       {cyan}▝█▘{blue}▟█▛       {cyan}  {blue}Shell{reset}         {shell}
-    {cyan}▟█████▛          {blue}▟█████▛    {cyan}  {blue}Uptime{reset}        {uptime}
-    {cyan}   ▟█▛{blue}▗█▖       {blue}▟█▛         {cyan}  {blue}Desktop{reset}       {desktop}
-    {cyan}  ▝█▛  {blue}██▖{cyan}▗▄▄▄▄▄▄▄▄▄▄▄      {cyan}󰍛  {blue}Memory{reset}        {memory_usage}
-    {cyan}   ▝  {blue}▟█▜█▖{cyan}▀▀▀▀▀██▛▀▀▘      {cyan}󱥎  {blue}Storage (/){reset}   {storage}
-    {blue}     ▟█▘ ▜█▖    {cyan}▝█▛         {cyan}  {blue}Colors{reset}        {colors}\n\n"
-  )?;
+  if CUSTOM_LOGO.is_empty() {
+    // Default two-tone NixOS logo rendered as a single write! pass.
+    core::fmt::write(
+      &mut w,
+      format_args!(
+        "\n    {b}     ▟█▖    {cy}▝█▙ ▗█▛         {user_info} ~{rs}\n    {b}  \
+         ▗▄▄▟██▄▄▄▄▄{cy}▝█▙█▛  {b}▖       {cy}\u{F313}  {b}System{rs}        \
+         {os_name}\n    {b}  ▀▀▀▀▀▀▀▀▀▀▀▘{cy}▝██  {b}▟█▖      {cy}\u{E712}  \
+         {b}Kernel{rs}        {kernel_version}\n    {cy}     ▟█▛       \
+         {cy}▝█▘{b}▟█▛       {cy}\u{E795}  {b}Shell{rs}         {shell}\n    \
+         {cy}▟█████▛          {b}▟█████▛    {cy}\u{F017}  {b}Uptime{rs}        \
+         {uptime}\n    {cy}   ▟█▛{b}▗█▖       {b}▟█▛         {cy}\u{F2D2}  \
+         {b}Desktop{rs}       {desktop}\n    {cy}  ▝█▛  \
+         {b}██▖{cy}▗▄▄▄▄▄▄▄▄▄▄▄      {cy}\u{F035B}  {b}Memory{rs}        \
+         {memory_usage}\n    {cy}   ▝  {b}▟█▜█▖{cy}▀▀▀▀▀██▛▀▀▘      \
+         {cy}\u{F194E}  {b}Storage (/){rs}   {storage}\n    {b}     ▟█▘ ▜█▖    \
+         {cy}▝█▛         {cy}\u{E22B}  {b}Colors{rs}        {colors}\n\n",
+        b = c.blue,
+        cy = c.cyan,
+        rs = c.reset,
+        user_info = user_info,
+        os_name = os_name,
+        kernel_version = kernel_version,
+        shell = shell,
+        uptime = uptime,
+        desktop = desktop,
+        memory_usage = memory_usage,
+        storage = storage,
+        colors = colors,
+      ),
+    )
+    .ok();
+  } else {
+    // Custom logo is 9 lines from MICROFETCH_LOGO env var, one per info row.
+    // Lines beyond 9 are ignored; missing lines render as empty.
+    let mut lines = CUSTOM_LOGO.split('\n');
+    let logo_rows: [&str; 9] =
+      core::array::from_fn(|_| lines.next().unwrap_or(""));
 
-  let len =
-    usize::try_from(cursor.position()).expect("cursor position fits usize");
-  // Direct syscall to avoid stdout buffering allocation
-  let written = unsafe { sys_write(1, buf.as_ptr(), len) };
+    // Row format mirrors the default logo path exactly.
+    let rows: [(&str, &str, &str, &str, &str); 9] = [
+      ("", "", user_info.as_str(), "        ", " ~"),
+      ("\u{F313}  ", "System", os_name.as_str(), "        ", ""),
+      (
+        "\u{E712}  ",
+        "Kernel",
+        kernel_version.as_str(),
+        "        ",
+        "",
+      ),
+      ("\u{E795}  ", "Shell", shell.as_str(), "         ", ""),
+      ("\u{F017}  ", "Uptime", uptime.as_str(), "        ", ""),
+      ("\u{F2D2}  ", "Desktop", desktop.as_str(), "       ", ""),
+      (
+        "\u{F035B}  ",
+        "Memory",
+        memory_usage.as_str(),
+        "        ",
+        "",
+      ),
+      ("\u{F194E}  ", "Storage (/)", storage.as_str(), "   ", ""),
+      ("\u{E22B}  ", "Colors", colors.as_str(), "        ", ""),
+    ];
+
+    core::fmt::write(&mut w, format_args!("\n")).ok();
+    for i in 0..9 {
+      let (icon, key, value, spacing, suffix) = rows[i];
+      if key.is_empty() {
+        // Row 1 has  no icon/key, just logo + user_info
+        core::fmt::write(
+          &mut w,
+          format_args!(
+            "    {cy}{logo}{rs}  {value}{suffix}\n",
+            cy = c.cyan,
+            rs = c.reset,
+            logo = logo_rows[i],
+            value = value,
+            suffix = suffix,
+          ),
+        )
+        .ok();
+      } else {
+        core::fmt::write(
+          &mut w,
+          format_args!(
+            "    {cy}{logo}{rs}  \
+             {cy}{icon}{b}{key}{rs}{spacing}{value}{suffix}\n",
+            cy = c.cyan,
+            b = c.blue,
+            rs = c.reset,
+            logo = logo_rows[i],
+            icon = icon,
+            key = key,
+            spacing = spacing,
+            value = value,
+            suffix = suffix,
+          ),
+        )
+        .ok();
+      }
+    }
+    core::fmt::write(&mut w, format_args!("\n")).ok();
+  }
+
+  // Single syscall for the entire output.
+  let out = w.written();
+  let written = unsafe { sys_write(1, out.as_ptr(), out.len()) };
   if written < 0 {
-    return Err(io::Error::last_os_error().into());
+    #[allow(clippy::cast_possible_truncation)]
+    return Err(Error::OsError(written as i32));
   }
-  #[allow(clippy::cast_sign_loss)] // non-negative verified by the guard above
-  if written as usize != len {
-    return Err(
-      io::Error::new(io::ErrorKind::WriteZero, "partial write to stdout")
-        .into(),
-    );
+
+  #[allow(clippy::cast_sign_loss)]
+  if written as usize != out.len() {
+    return Err(Error::WriteError);
   }
+
   Ok(())
 }
 
+/// Print version information using direct syscall.
+fn print_version() {
+  const VERSION: &str = concat!("Microfetch ", env!("CARGO_PKG_VERSION"), "\n");
+  unsafe {
+    let _ = sys_write(1, VERSION.as_ptr(), VERSION.len());
+  }
+}
+
+/// Check if --version was passed via argc/argv.
+///
+/// # Safety
+///
+/// This function must be called with valid argc and argv from the program entry
+/// point.
+unsafe fn check_version_flag(argc: i32, argv: *const *const u8) -> bool {
+  if argc < 2 {
+    return false;
+  }
+  // SAFETY: argv is a valid array of argc pointers
+  let arg1 = unsafe { *argv.add(1) };
+  if arg1.is_null() {
+    return false;
+  }
+  // Check if arg1 is "--version"
+  let version_flag = b"--version\0";
+  for (i, &b) in version_flag.iter().enumerate() {
+    // SAFETY: arg1 is a valid C string
+    let arg_byte = unsafe { *arg1.add(i) };
+    if arg_byte != b {
+      return false;
+    }
+  }
+  true
+}
+
 /// Main entry point for microfetch - can be called by the binary crate
-/// or by other consumers of the library
+/// or by other consumers of the library.
+///
+/// # Arguments
+///
+/// * `argc` - Argument count from main
+/// * `argv` - Argument vector from main
 ///
 /// # Errors
 ///
 /// Returns an error if any system call fails
+///
+/// # Safety
+///
+/// argv must be a valid null-terminated array of C strings.
 #[cfg_attr(feature = "hotpath", hotpath::main)]
-pub fn run() -> Result<(), Box<dyn std::error::Error>> {
-  if Some("--version") == std::env::args().nth(1).as_deref() {
-    println!("Microfetch {}", env!("CARGO_PKG_VERSION"));
-  } else {
+pub unsafe fn run(argc: i32, argv: *const *const u8) -> Result<(), Error> {
+  if unsafe { check_version_flag(argc, argv) } {
+    print_version();
+    return Ok(());
+  }
+
   let utsname = UtsName::uname()?;
   let fields = Fields {
     user_info:      system::get_username_and_hostname(&utsname),
@@ -156,7 +542,6 @@ pub fn run() -> Result<(), Box<dyn std::error::Error>> {
     colors:         colors::print_dots(),
   };
   print_system_info(&fields)?;
-  }
 
   Ok(())
 }

crates/lib/src/release.rs

@@ -1,6 +1,6 @@
-use std::{fmt::Write as _, io};
+use alloc::string::String;
 
-use crate::{UtsName, syscall::read_file_fast};
+use crate::{Error, UtsName, syscall::read_file_fast};
 
 #[must_use]
 #[cfg_attr(feature = "hotpath", hotpath::measure)]
@@ -13,7 +13,14 @@ pub fn get_system_info(utsname: &UtsName) -> String {
   let capacity = sysname.len() + 1 + release.len() + 2 + machine.len() + 1;
   let mut result = String::with_capacity(capacity);
 
-  write!(result, "{sysname} {release} ({machine})").unwrap();
+  // Manual string construction instead of write! macro
+  result.push_str(sysname);
+  result.push(' ');
+  result.push_str(release);
+  result.push_str(" (");
+  result.push_str(machine);
+  result.push(')');
+
   result
 }
 
@@ -23,7 +30,7 @@ pub fn get_system_info(utsname: &UtsName) -> String {
 ///
 /// Returns an error if `/etc/os-release` cannot be read.
 #[cfg_attr(feature = "hotpath", hotpath::measure)]
-pub fn get_os_pretty_name() -> Result<String, io::Error> {
+pub fn get_os_pretty_name() -> Result<String, Error> {
   // Fast byte-level scanning for PRETTY_NAME=
   const PREFIX: &[u8] = b"PRETTY_NAME=";
 
@@ -31,7 +38,7 @@ pub fn get_os_pretty_name() -> Result<String, io::Error> {
 
   // Use fast syscall-based file reading
   let bytes_read = read_file_fast("/etc/os-release", &mut buffer)
-    .map_err(|e| io::Error::from_raw_os_error(-e))?;
+    .map_err(Error::from_raw_os_error)?;
   let content = &buffer[..bytes_read];
 
   let mut offset = 0;
@@ -66,5 +73,5 @@ pub fn get_os_pretty_name() -> Result<String, io::Error> {
     offset += line_end + 1;
   }
 
-  Ok("Unknown".to_owned())
+  Ok(String::from("Unknown"))
 }

crates/lib/src/system.rs

@@ -1,37 +1,39 @@
-use std::{ffi::OsStr, fmt::Write as _, io, mem::MaybeUninit};
+use alloc::string::String;
+use core::mem::MaybeUninit;
 
 use crate::{
+  Error,
   UtsName,
-  colors::COLORS,
+  colors::Colors,
   syscall::{StatfsBuf, read_file_fast, sys_statfs},
 };
 
 #[must_use]
 #[cfg_attr(feature = "hotpath", hotpath::measure)]
 pub fn get_username_and_hostname(utsname: &UtsName) -> String {
-  let username_os = std::env::var_os("USER");
-  let username = username_os
-    .as_deref()
-    .and_then(OsStr::to_str)
-    .unwrap_or("unknown_user");
+  let username = crate::getenv_str("USER").unwrap_or("unknown_user");
   let hostname = utsname.nodename().to_str().unwrap_or("unknown_host");
 
-  let capacity = COLORS.yellow.len()
+  // Get colors (checking NO_COLOR only once)
+  let no_color = crate::colors::is_no_color();
+  let colors = Colors::new(no_color);
+
+  let capacity = colors.yellow.len()
     + username.len()
-    + COLORS.red.len()
+    + colors.red.len()
     + 1
-    + COLORS.green.len()
+    + colors.green.len()
     + hostname.len()
-    + COLORS.reset.len();
+    + colors.reset.len();
   let mut result = String::with_capacity(capacity);
 
-  result.push_str(COLORS.yellow);
+  result.push_str(colors.yellow);
   result.push_str(username);
-  result.push_str(COLORS.red);
+  result.push_str(colors.red);
   result.push('@');
-  result.push_str(COLORS.green);
+  result.push_str(colors.green);
   result.push_str(hostname);
-  result.push_str(COLORS.reset);
+  result.push_str(colors.reset);
 
   result
 }
@@ -39,13 +41,12 @@ pub fn get_username_and_hostname(utsname: &UtsName) -> String {
 #[must_use]
 #[cfg_attr(feature = "hotpath", hotpath::measure)]
 pub fn get_shell() -> String {
-  let shell_os = std::env::var_os("SHELL");
-  let shell = shell_os.as_deref().and_then(OsStr::to_str).unwrap_or("");
+  let shell = crate::getenv_str("SHELL").unwrap_or("");
   let start = shell.rfind('/').map_or(0, |i| i + 1);
   if shell.is_empty() {
-    "unknown_shell".into()
+    String::from("unknown_shell")
   } else {
-    shell[start..].into()
+    String::from(&shell[start..])
   }
 }
 
@@ -56,12 +57,12 @@ pub fn get_shell() -> String {
 /// Returns an error if the filesystem information cannot be retrieved.
 #[cfg_attr(feature = "hotpath", hotpath::measure)]
 #[allow(clippy::cast_precision_loss)]
-pub fn get_root_disk_usage() -> Result<String, io::Error> {
+pub fn get_root_disk_usage() -> Result<String, Error> {
   let mut vfs = MaybeUninit::<StatfsBuf>::uninit();
   let path = b"/\0";
 
   if unsafe { sys_statfs(path.as_ptr(), vfs.as_mut_ptr()) } != 0 {
-    return Err(io::Error::last_os_error());
+    return Err(Error::last_os_error());
   }
 
   let vfs = unsafe { vfs.assume_init() };
@@ -77,18 +78,96 @@ pub fn get_root_disk_usage() -> Result<String, io::Error> {
   let used_size = used_size as f64 / (1024.0 * 1024.0 * 1024.0);
   let usage = (used_size / total_size) * 100.0;
 
+  let no_color = crate::colors::is_no_color();
+  let colors = Colors::new(no_color);
+
   let mut result = String::with_capacity(64);
-  write!(
-    result,
-    "{used_size:.2} GiB / {total_size:.2} GiB ({cyan}{usage:.0}%{reset})",
-    cyan = COLORS.cyan,
-    reset = COLORS.reset,
-  )
-  .unwrap();
+
+  // Manual float formatting
+  write_float(&mut result, used_size, 2);
+  result.push_str(" GiB / ");
+  write_float(&mut result, total_size, 2);
+  result.push_str(" GiB (");
+  result.push_str(colors.cyan);
+  write_float(&mut result, usage, 0);
+  result.push('%');
+  result.push_str(colors.reset);
+  result.push(')');
 
   Ok(result)
 }
 
+/// Write a float to string with specified decimal places
+#[allow(
+  clippy::cast_sign_loss,
+  clippy::cast_possible_truncation,
+  clippy::cast_precision_loss
+)]
+fn write_float(s: &mut String, val: f64, decimals: u32) {
+  // Handle integer part
+  let int_part = val as u64;
+  write_u64(s, int_part);
+
+  if decimals > 0 {
+    s.push('.');
+
+    // Calculate fractional part
+    let mut frac = val - int_part as f64;
+    for _ in 0..decimals {
+      frac *= 10.0;
+      let digit = frac as u8;
+      s.push((b'0' + digit) as char);
+      frac -= f64::from(digit);
+    }
+  }
+}
+
+/// Round an f64 to nearest integer (`f64::round` is not in core)
+#[allow(
+  clippy::cast_precision_loss,
+  clippy::cast_possible_truncation,
+  clippy::cast_sign_loss
+)]
+fn round_f64(x: f64) -> f64 {
+  if x >= 0.0 {
+    let int_part = x as u64 as f64;
+    let frac = x - int_part;
+    if frac >= 0.5 {
+      int_part + 1.0
+    } else {
+      int_part
+    }
+  } else {
+    let int_part = (-x) as u64 as f64;
+    let frac = -x - int_part;
+    if frac >= 0.5 {
+      -(int_part + 1.0)
+    } else {
+      -int_part
+    }
+  }
+}
+
+/// Write a u64 to string
+fn write_u64(s: &mut String, mut n: u64) {
+  if n == 0 {
+    s.push('0');
+    return;
+  }
+
+  let mut buf = [0u8; 20];
+  let mut i = 20;
+
+  while n > 0 {
+    i -= 1;
+    buf[i] = b'0' + (n % 10) as u8;
+    n /= 10;
+  }
+
+  // SAFETY: buf contains only ASCII digits
+  s.push_str(unsafe { core::str::from_utf8_unchecked(&buf[i..]) });
+}
+
 /// Fast integer parsing without stdlib overhead
 #[inline]
 fn parse_u64_fast(s: &[u8]) -> u64 {
@@ -109,16 +188,16 @@ fn parse_u64_fast(s: &[u8]) -> u64 {
 ///
 /// Returns an error if `/proc/meminfo` cannot be read.
 #[cfg_attr(feature = "hotpath", hotpath::measure)]
-pub fn get_memory_usage() -> Result<String, io::Error> {
+pub fn get_memory_usage() -> Result<String, Error> {
   #[cfg_attr(feature = "hotpath", hotpath::measure)]
-  fn parse_memory_info() -> Result<(f64, f64), io::Error> {
+  fn parse_memory_info() -> Result<(f64, f64), Error> {
     let mut total_memory_kb = 0u64;
     let mut available_memory_kb = 0u64;
     let mut buffer = [0u8; 1024];
 
     // Use fast syscall-based file reading
     let bytes_read = read_file_fast("/proc/meminfo", &mut buffer)
-      .map_err(|e| io::Error::from_raw_os_error(-e))?;
+      .map_err(Error::from_raw_os_error)?;
     let meminfo = &buffer[..bytes_read];
 
     // Fast scanning for MemTotal and MemAvailable
@@ -168,17 +247,22 @@ pub fn get_memory_usage() -> Result<String, io::Error> {
 
   let (used_memory, total_memory) = parse_memory_info()?;
   #[allow(clippy::cast_possible_truncation, clippy::cast_sign_loss)]
-  let percentage_used = (used_memory / total_memory * 100.0).round() as u64;
+  let percentage_used = round_f64(used_memory / total_memory * 100.0) as u64;
+
+  let no_color = crate::colors::is_no_color();
+  let colors = Colors::new(no_color);
 
   let mut result = String::with_capacity(64);
-  write!(
-    result,
-    "{used_memory:.2} GiB / {total_memory:.2} GiB \
-     ({cyan}{percentage_used}%{reset})",
-    cyan = COLORS.cyan,
-    reset = COLORS.reset,
-  )
-  .unwrap();
+
+  write_float(&mut result, used_memory, 2);
+  result.push_str(" GiB / ");
+  write_float(&mut result, total_memory, 2);
+  result.push_str(" GiB (");
+  result.push_str(colors.cyan);
+  write_u64(&mut result, percentage_used);
+  result.push('%');
+  result.push_str(colors.reset);
+  result.push(')');
 
   Ok(result)
 }

crates/lib/src/uptime.rs

@@ -1,6 +1,7 @@
-use std::{io, mem::MaybeUninit};
+use alloc::string::String;
+use core::mem::MaybeUninit;
 
-use crate::syscall::sys_sysinfo;
+use crate::{Error, syscall::sys_sysinfo};
 
 /// Faster integer to string conversion without the formatting overhead.
 #[inline]
@@ -16,7 +17,8 @@ fn itoa(mut n: u64, buf: &mut [u8]) -> &str {
     n /= 10;
   }
 
-  unsafe { std::str::from_utf8_unchecked(&buf[i..]) }
+  // SAFETY: We only wrote ASCII digits
+  unsafe { core::str::from_utf8_unchecked(&buf[i..]) }
 }
 
 /// Gets the current system uptime.
@@ -25,11 +27,11 @@ fn itoa(mut n: u64, buf: &mut [u8]) -> &str {
 ///
 /// Returns an error if the system uptime cannot be retrieved.
 #[cfg_attr(feature = "hotpath", hotpath::measure)]
-pub fn get_current() -> Result<String, io::Error> {
+pub fn get_current() -> Result<String, Error> {
   let uptime_seconds = {
     let mut info = MaybeUninit::uninit();
     if unsafe { sys_sysinfo(info.as_mut_ptr()) } != 0 {
-      return Err(io::Error::last_os_error());
+      return Err(Error::last_os_error());
     }
     #[allow(clippy::cast_sign_loss)]
     unsafe {

docs/README.md

@@ -19,12 +19,12 @@
 
 [fastfetch]: https://github.com/fastfetch-cli/fastfetch
 
-Stupidly small and simple, laughably fast and pretty fetch tool. Written in Rust
-for speed and ease of maintainability. Runs in a _fraction of a millisecond_ and
-displays _most_ of the nonsense you'd see posted on r/unixporn or other internet
-communities. Aims to replace [fastfetch] on my personal system, but
-[probably not yours](#customizing). Though, you are more than welcome to use it
-on your system: it is pretty _[fast](#benchmarks)_...
+Stupidly small and simple, laughably fast, and pretty fetch tool. Written
+(mostly) in Rust for speed and ease of maintainability. Runs in a _fraction of a
+millisecond_ and displays _most_ of the nonsense you'd see posted on r/unixporn
+or other internet communities. Aims to replace [fastfetch] on my personal
+system, but [probably not yours](#customizing). Though, you are more than
+welcome to use it on your system: it is pretty _[fast](#benchmarks)_...
 
 <p align="center">
   <br/>
@@ -40,10 +40,10 @@ on your system: it is pretty _[fast](#benchmarks)_...
 
 - Fast
 - Really fast
-- Minimal dependencies
-- Tiny binary (~370kb [^1])
-- Actually really fast
-- Cool NixOS logo (other, inferior, distros are not supported)
+- No dependencies (not even libc!)
+- Tiny binary (~24kb)
+- Actually _really_ fast
+- Cool NixOS logo, with support for custom logo text
 - Reliable detection of following info:
   - Hostname/Username
   - Kernel
@@ -57,12 +57,9 @@ on your system: it is pretty _[fast](#benchmarks)_...
   - Shell Colors
 - Did I mention fast?
 - Respects [`NO_COLOR` spec](https://no-color.org/)
-- Funny [^2]
+- Funny [^1]
 
-[^1]: With the Mold linker, which is enabled by default in the Flake package,
-    the binary size is roughly 350kb. That's nearly 20kb reduction in size :)
-
-[^2]: I don't know how else to describe the (unhealthy) amount of handwritten
+[^1]: I don't know how else to describe the (unhealthy) amount of handwritten
     assembly that was written in order to make Microfetch faster.
 
 ## Motivation
@@ -70,12 +67,12 @@ on your system: it is pretty _[fast](#benchmarks)_...
 [Rube-Goldmark Machine]: https://en.wikipedia.org/wiki/Rube_Goldberg_machine
 
 Fastfetch, as its name _probably_ already hinted, is a very fast fetch tool
-written in C. I used to use Fastfetch on my systems, but I eventually came to
+written in C. I _used to_ use Fastfetch on my systems, but I eventually came to
 the realization that I am _not interested in any of its additional features_. I
 don't use Sixel, I don't change my configuration more than maybe once a year and
-I don't even display most of the fields that it does. Sure the configurability
-is nice and I can configure the defaults that I do not like but how often do I
-really do that?
+I don't even display most of the fields that it has. Sure, the configurability
+is nice and _I could_ configure the defaults that I do not like... but how often
+do I really do that?
 
 Since I already enjoy programming challenges, and don't use a fetch program that
 often, I eventually came to try and answer the question _how fast can I make my
@@ -84,24 +81,29 @@ and put in my `~/.bashrc` but is _actually_ incredibly fast because it opts out
 of all the customization options provided by tools such as Fastfetch. Since
 Fetch scripts are kind of a coming-of-age ritual for most Linux users, I've
 decided to use it on my system. You also might be interested if you like the
-defaults and like speed.
+defaults and like speed. Ultimately, Microfetch a small, opinionated binary with
+a nice size that doesn't bother me, and _incredible_ speed. Customization? No
+thank you.
 
-Ultimately, it's a small, opinionated binary with a nice size that doesn't
-bother me, and incredible speed. Customization? No thank you. I cannot
-re-iterate it enough, Microfetch is _annoyingly fast_. It does not, however,
-solve a technical problem. The "problem" Microfetch solves is entirely
-self-imposed. On the matter of _size_, the project is written in Rust, which
-comes at the cost of "bloated" dependency trees and the increased build times,
-but we make an extended effort to keep the dependencies minimal and build times
-manageable. The latter is also very easily mitigated with Nix's binary cache
-systems. Since Microfetch is already in Nixpkgs, you are recommended to use it
-to utilize the binary cache properly. The usage of Rust _is_ nice, however,
-since it provides us with incredible tooling and a very powerful language that
-allows for Microfetch to be as fast as possible. ~~Sure C could've been used
-here as well, but do you think I hate myself?~~ Microfetch now features
-handwritten assembly to unsafely optimize some areas. In hindsight you all
-should have seen this coming. Is it faster? Yes. Should you use this? If you
-want to.
+I cannot re-iterate it enough, Microfetch is _annoyingly fast_. It, however,
+does not solve a real technical problem. The "problem" Microfetch "solves" is
+entirely self-imposed. I want a fast, _almost_ zero-cost command invocation and
+for it to not take that much space on my system. Thanks to the nature of Rust,
+Microfetch is _fast_. Rust does, or well, _did_ mean "bloated" dependency trees
+and slightly increased build times, though, as of 0.5.0 Microfetch has
+(voluntarily) dropped both `std` and `libc`. You can go check the numbers for
+the speed impact (hint: it's much better) but we also have little to no concerns
+left about build times and the binary size. Build times are also _very easily_
+mitigated with Nix's binary cache systems, and since Microfetch is already in
+Nixpkgs you are strongly encouraged to use `pkgs.microfetch` over the flake. The
+usage of Rust _is_ quite nice, however, since it provides us with incredible
+tooling and a very powerful language that allows for Microfetch to be as fast as
+possible.
+
+Surely C would've been a smaller choice, but I like Rust more. Microfetch _also_
+features a whole bunch of handwritten assembly with per-platform support to
+_unsafely_ optimize most syscalls. In hindsight you all should have seen this
+coming. Is it faster? Yes. Is it better? Uh, yes. Should you use this? Yes.
 
 Also see: [Rube-Goldmark Machine]
 
@@ -232,20 +234,11 @@ interested in Microfetch tailored to their distributions.
 
 ## Customizing
 
-You can't*.
-
-### Why?
-
-Customization, of most kinds, is "expensive": I could try reading environment
-variables, parse command-line arguments or read a configuration file to allow
-configuring various fields but those inflate execution time and the resource
-consumption by a lot. Since Microfetch is closer to a code golf challenge than a
-program that attempts to fill a gap, I have elected not to make this trade. This
-is, of course, not without a solution.
+You can't*
 
 ### Really?
 
-[main module]: ./src/main.rs
+[main module]: ./microfetch/src/main.rs
 [discussions tab]: https://github.com/NotAShelf/microfetch/discussions
 
 To be fair, you _can_ customize Microfetch by, well, patching it. It is
@@ -263,6 +256,36 @@ The Nix package allows passing patches in a streamlined manner by passing
 share your derivations with people. Feel free to use the [discussions tab] to
 share your own variants of Microfetch!
 
+The real reason behind lack of customizability is that customization, of most
+kinds, is "expensive": reading environment variables, parsing command-line
+arguments or reading a configuration file inflates execution time and resource
+consumption. Since Microfetch is closer to a code golf challenge than a program
+that attempts to fill a gap, runtime configuration is not supported. Patching
+the source is the only way to make changes that do not compromise on speed. The
+exception to this, as described below, is the custom logo support.
+
+### Logo
+
+Microfetch used to be impossible to customize without patching. Fortunately it's
+possible now to customize the logo to support your distribution. This is
+best-effort, but should work for most cases as long as you adhere to the
+constraints.
+
+To use a custom logo, set the `MICROFETCH_LOGO` environment variable to 9
+newline-separated lines of ASCII or Unicode art when building:
+
+```bash
+# Pass your logo text with MICROFETCH_LOGO.
+$ MICROFETCH_LOGO="$(cat my_logo.txt)" cargo build --release
+```
+
+Each line corresponds to one info row. Nerd Font glyphs for labels (System,
+Kernel, Shell, etc.) are rendered automatically. An unset variable uses the
+built-in two-tone NixOS logo.
+
+Keep in mind that the custom logo **is not padded**. You will need to mind the
+spaces if you're providing a custom logo for some sort.
+
 ## Contributing
 
 I will, mostly, reject feature additions. This is not to say you should avoid
@@ -312,4 +335,5 @@ Microfetch. I might have missed your name here, but you have my thanks.
 
 ## License
 
-Microfetch is licensed under [GPL3](LICENSE). See the license file for details.
+This project is released under GNU Public Licence version 3 **only**. See the
+[license](../LICENSE) for more details.

microfetch/Cargo.toml

@@ -12,6 +12,8 @@ publish                = false
 
 [dependencies]
 hotpath                    = { optional = true, version = "0.14.0" }
+microfetch-alloc.workspace = true
+microfetch-asm.workspace   = true
 microfetch-lib.workspace   = true
 
 [features]

microfetch/build.rs

@@ -0,0 +1,17 @@
+fn main() {
+  // These flags only apply to the microfetch binary, not to proc-macro crates
+  // or other host-compiled artifacts.
+
+  // No C runtime, we provide _start ourselves
+  println!("cargo:rustc-link-arg-bin=microfetch=-nostartfiles");
+  // Fully static, no dynamic linker, no .interp/.dynsym/.dynamic overhead
+  println!("cargo:rustc-link-arg-bin=microfetch=-static");
+  // Remove unreferenced input sections
+  println!("cargo:rustc-link-arg-bin=microfetch=-Wl,--gc-sections");
+  // Strip all symbol table entries
+  println!("cargo:rustc-link-arg-bin=microfetch=-Wl,--strip-all");
+  // Omit the .note.gnu.build-id section
+  println!("cargo:rustc-link-arg-bin=microfetch=-Wl,--build-id=none");
+  // Disable RELRO (removes relro_padding)
+  println!("cargo:rustc-link-arg-bin=microfetch=-Wl,-z,norelro");
+}

microfetch/src/main.rs

@@ -1,3 +1,112 @@
-fn main() -> Result<(), Box<dyn std::error::Error>> {
-  microfetch_lib::run()
+#![no_std]
+#![no_main]
+
+extern crate alloc;
+
+use core::{arch::naked_asm, panic::PanicInfo};
+
+use microfetch_alloc::BumpAllocator;
+// Re-export libc replacement functions from asm crate
+pub use microfetch_asm::{memcpy, memset, strlen};
+use microfetch_asm::{entry_rust, sys_exit, sys_write};
+
+#[cfg(target_arch = "x86_64")]
+#[unsafe(no_mangle)]
+#[unsafe(naked)]
+unsafe extern "C" fn _start() {
+  naked_asm!(
+    "mov rdi, rsp",
+    "and rsp, -16",
+    "call {entry_rust}",
+    "mov rdi, rax",
+    "mov rax, 60",
+    "syscall",
+    entry_rust = sym entry_rust,
+  );
+}
+
+#[cfg(target_arch = "aarch64")]
+#[unsafe(no_mangle)]
+#[unsafe(naked)]
+unsafe extern "C" fn _start() {
+  naked_asm!(
+    "mov x0, sp",
+    "mov x9, sp",
+    "and x9, x9, #-16",
+    "mov sp, x9",
+    "bl {entry_rust}",
+    "mov x0, x0",
+    "mov x8, 93",
+    "svc #0",
+    entry_rust = sym entry_rust,
+  );
+}
+
+#[cfg(target_arch = "riscv64")]
+#[unsafe(no_mangle)]
+#[unsafe(naked)]
+unsafe extern "C" fn _start() {
+  naked_asm!(
+    "mv a0, sp",
+    "andi sp, sp, -16",
+    "call {entry_rust}",
+    "mv a0, a0",
+    "li a7, 93",
+    "ecall",
+    entry_rust = sym entry_rust,
+  );
+}
+
+// Global allocator
+#[global_allocator]
+static ALLOCATOR: BumpAllocator = BumpAllocator::new();
+
+/// Main application entry point. Called by the asm crate's entry point
+/// after setting up argc, argv, and envp.
+///
+/// # Safety
+///
+/// argv must be a valid pointer to an array of argc C strings.
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn main(argc: i32, argv: *const *const u8) -> i32 {
+  // Calculate envp from argv. On Linux, envp is right after argv on the stack
+  // but I bet 12 cents that there will be at least one exception.
+  let argc_usize = usize::try_from(argc).unwrap_or(0);
+  let envp = unsafe { argv.add(argc_usize + 1) };
+
+  // Initialize the environment pointer
+  unsafe {
+    microfetch_lib::init_env(envp);
+  }
+
+  // Run the main application logic
+  match unsafe { microfetch_lib::run(argc, argv) } {
+    Ok(()) => 0,
+    Err(e) => {
+      let msg = alloc::format!("Error: {e}\n");
+      let _ = unsafe { sys_write(2, msg.as_ptr(), msg.len()) };
+      1
+    },
+  }
+}
+
+#[cfg(not(test))]
+#[panic_handler]
+fn panic(_info: &PanicInfo) -> ! {
+  const PANIC_MSG: &[u8] = b"panic\n";
+  unsafe {
+    let _ = sys_write(2, PANIC_MSG.as_ptr(), PANIC_MSG.len());
+    sys_exit(1)
+  }
+}
+
+// Stubs for Rust exception handling
+#[cfg(not(test))]
+#[unsafe(no_mangle)]
+const extern "C" fn rust_eh_personality() {}
+
+#[cfg(not(test))]
+#[unsafe(no_mangle)]
+extern "C" fn _Unwind_Resume() -> ! {
+  unsafe { sys_exit(1) }
 }

nix/package.nix

@@ -1,22 +1,13 @@
 {
   lib,
-  stdenv,
-  stdenvAdapters,
   rustPlatform,
   llvm,
-  useMold ? stdenv.isLinux,
 }: let
-  toml = (lib.importTOML ../Cargo.toml).package;
-  pname = toml.name;
+  pname = "microfetch";
+  toml = (lib.importTOML ../Cargo.toml).workspace.package;
   inherit (toml) version;
-
-  # Select stdenv based on useMold flag
-  stdenv =
-    if useMold
-    then stdenvAdapters.useMoldLinker llvm.stdenv
-    else llvm.stdenv;
 in
-  rustPlatform.buildRustPackage.override {inherit stdenv;} {
+  rustPlatform.buildRustPackage.override {inherit (llvm) stdenv;} {
     inherit pname version;
     src = let
       fs = lib.fileset;
@@ -25,10 +16,12 @@ in
       fs.toSource {
         root = s;
         fileset = fs.unions [
-          (fs.fileFilter (file: builtins.any file.hasExt ["rs"]) (s + /src))
+          (s + /crates)
+          (s + /microfetch)
+          (s + /.cargo)
+          (s + /scripts/ld-wrapper)
           (s + /Cargo.lock)
           (s + /Cargo.toml)
-          (s + /benches)
         ];
       };
 
@@ -37,12 +30,6 @@ in
     buildNoDefaultFeatures = true;
     doCheck = false;
 
-    # Only set RUSTFLAGS for mold if useMold is enabled
-    env = lib.optionalAttrs useMold {
-      CARGO_LINKER = "clang";
-      RUSTFLAGS = "-C link-arg=-fuse-ld=mold";
-    };
-
     meta = {
       description = "Microscopic fetch script in Rust, for NixOS systems";
       homepage = "https://github.com/NotAShelf/microfetch";

scripts/ld-wrapper

@@ -0,0 +1,38 @@
+#!/usr/bin/env sh
+# Invoke mold, then strip junk sections from the output binary with objcopy.
+# This (more or less) removes sections that mold cannot discard itself, suck as:
+#  - .eh_frame / .eh_frame_hdr  - unwind tables from compiler_builtins
+#  - .dynstr                     - mold emits this, even for fully static binaries
+#  - .comment                   - compiler version string
+#
+#  We forward everything to mold via -fuse-ld, then post-process the output in place.
+
+set -eu
+
+# Locate the output file and detect static linking
+IS_STATIC=0
+OUTPUT=""
+prev=""
+for arg in "$@"; do
+	case "$arg" in
+		-static) IS_STATIC=1 ;;
+	esac
+	if [ "$prev" = "-o" ]; then
+		OUTPUT="$arg"
+	fi
+	prev="$arg"
+done
+
+# Invoke mold via the cc driver, forward all original arguments
+cc -fuse-ld=mold "$@"
+
+# Only strip sections from fully static binaries.
+# Dynamic executables (i.e. build scripts, proc-macros) need .dynstr at runtime.
+if [ "$IS_STATIC" = 1 ] && [ -n "$OUTPUT" ] && [ -f "$OUTPUT" ]; then
+	objcopy \
+		--remove-section=.eh_frame \
+		--remove-section=.eh_frame_hdr \
+		--remove-section=.dynstr \
+		--remove-section=.comment \
+		"$OUTPUT"
+fi