From 0049dc9cf781c65f5a633f51f0e705274853060c Mon Sep 17 00:00:00 2001
From: pommicket <pommicket@gmail.com>
Date: Tue, 8 Nov 2022 18:36:04 -0500
Subject: more info, SDL example

---
 src/linker.rs | 28 +++++++++++++++++++++++-----
 src/main.rs   | 23 ++++++++++++++++++++++-
 tests/sdl.c   | 30 ++++++++++++++++++++++++++++++
 3 files changed, 75 insertions(+), 6 deletions(-)
 create mode 100644 tests/sdl.c

diff --git a/src/linker.rs b/src/linker.rs
index fdc1f5b..c82d1d3 100644
--- a/src/linker.rs
+++ b/src/linker.rs
@@ -55,6 +55,14 @@ std::ofstream cout("/dev/stdout");
 std::ifstream cin("/dev/stdin");
 ```
 or use `printf`, `scanf` for smaller executables.
+
+Notes on executable size:
+
+- A bare minimum executable with libc is ~300 bytes, and
+  without libc is ~100 bytes.
+- Each external symbol requires 21 + 8n + l bytes in total,
+  where l is the length of the name, and n is the number of times
+  it is used. It (thankfully) doesn't seem to be worth it to use `dlsym`.
 */
 
 use crate::elf;
@@ -711,7 +719,7 @@ impl LinkerOutput {
 	}
 
 	/// output the executable.
-	pub fn write(&self, mut out: impl Write + Seek, entry_point: u64) -> LinkResult<()> {
+	pub fn write(&self, mut out: impl Write + Seek, entry_point: u64) -> LinkResult<LinkInfo> {
 		let u64_to_u32 = LinkError::u64_to_u32;
 		let usize_to_u32 = LinkError::usize_to_u32;
 
@@ -882,11 +890,21 @@ impl LinkerOutput {
 			};
 			out.write_all(&phdr_dynamic.to_bytes())?;
 		}
-
-		Ok(())
+		
+		out.seek(io::SeekFrom::End(0))?;
+		Ok(LinkInfo {
+			data_size: self.data.len() as u64,
+			exec_size: out.stream_position()?
+		})
 	}
 }
 
+/// info about linked executable
+pub struct LinkInfo {
+	pub exec_size: u64,
+	pub data_size: u64,
+}
+
 impl<'a> Linker<'a> {
 	pub const DEFAULT_CFLAGS: [&str; 6] = [
 		"-Wall",
@@ -1257,7 +1275,7 @@ impl<'a> Linker<'a> {
 	}
 
 	/// Link everything together.
-	pub fn link(&self, out: impl Write + Seek, entry: &str) -> LinkResult<()> {
+	pub fn link(&self, out: impl Write + Seek, entry: &str) -> LinkResult<LinkInfo> {
 		let mut exec = LinkerOutput::new(0x400000);
 		if self.bss_size > 0 {
 			exec.set_bss(0x70000000, self.bss_size);
@@ -1331,7 +1349,7 @@ impl<'a> Linker<'a> {
 	/// Instead, define `void <main/entry/something_else>(void)`, and make sure you call `exit`,
 	/// or do an exit system interrupt at the end of the function --- if you just return,
 	/// you'll get a segmentation fault.
-	pub fn link_to_file(&self, path: impl AsRef<path::Path>, entry: &str) -> Result<(), String> {
+	pub fn link_to_file(&self, path: impl AsRef<path::Path>, entry: &str) -> Result<LinkInfo, String> {
 		let path = path.as_ref();
 		let mut out_options = fs::OpenOptions::new();
 		out_options.write(true).create(true).truncate(true);
diff --git a/src/main.rs b/src/main.rs
index 585d241..9ff86d9 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,6 +5,8 @@
 
 extern crate clap;
 
+use std::io;
+use io::Write;
 use clap::Parser;
 
 #[cfg(target_endian = "big")]
@@ -52,6 +54,9 @@ struct Args {
 	/// C++ compiler flags
 	#[arg(long = "cxxflags", default_values = linker::Linker::DEFAULT_CXXFLAGS)]
 	cxxflags: Vec<String>,
+	/// verbose mode
+	#[arg(short = 'v', long = "verbose")]
+	verbose: bool,
 }
 
 fn main_() -> Result<(), String> {
@@ -96,10 +101,26 @@ fn main_() -> Result<(), String> {
 	}
 
 	for input in inputs.iter() {
+		if args.verbose {
+			println!("processing source file {input}...");
+		}
 		linker.add_input(input)?;
 	}
 
-	linker.link_to_file(&args.output, &args.entry)
+	if args.verbose {
+		print!("linking {}... ", args.output);
+	}
+	
+	io::stdout().flush().unwrap_or(());
+	let info = linker.link_to_file(&args.output, &args.entry)?;
+	
+	if args.verbose {
+		println!("\x1b[92msuccess!\x1b[0m");
+		println!("data size:      {:7} bytes", info.data_size);
+		println!("executable size:{:7} bytes", info.exec_size);
+	}
+	
+	Ok(())
 }
 
 fn main() {
diff --git a/tests/sdl.c b/tests/sdl.c
new file mode 100644
index 0000000..a3c3d8f
--- /dev/null
+++ b/tests/sdl.c
@@ -0,0 +1,30 @@
+#define SDL_DISABLE_IMMINTRIN_H
+#include <SDL2/SDL.h>
+#include <GL/glcorearb.h>
+#include <stdio.h>
+#include <stdbool.h>
+
+int main(void) {
+	SDL_Init(SDL_INIT_EVERYTHING);
+	SDL_Window *window = SDL_CreateWindow("hi", 0, 0, 1280, 720, SDL_WINDOW_SHOWN|SDL_WINDOW_OPENGL);
+	SDL_GLContext ctx = SDL_GL_CreateContext(window);
+	PFNGLCLEARPROC glClear = SDL_GL_GetProcAddress("glClear");
+	PFNGLCLEARCOLORPROC glClearColor = SDL_GL_GetProcAddress("glClearColor");
+	SDL_GL_SetSwapInterval(1);
+	while (true) {
+		SDL_Event event;
+		while (SDL_PollEvent(&event)) {
+			if (event.type == SDL_QUIT) {
+				return 0;
+			}
+		}
+		glClearColor(1, 1, 1, 1);
+		glClear(GL_COLOR_BUFFER_BIT);
+		SDL_GL_SwapWindow(window);
+	}
+	(void)ctx;
+}
+
+void entry(void) {
+	exit(main());
+}
-- 
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