Fix build, start using libc instead of core

Author: osa1

rts/Makefile

@@ -21,7 +21,7 @@ TOMMATHFILES = \
 MUSLFILES = \
   pow pow_data sin cos tan asin acos atan atan2 exp exp_data log log_data fmod \
   towctrans iswspace iswupper iswlower iswalpha wcschr wcslen \
-  floor scalbn frexp strnlen memchr memset memcpy snprintf vsnprintf vfprintf \
+  floor scalbn frexp strnlen memchr printf snprintf vsnprintf vfprintf \
   __math_oflow __math_uflow __math_xflow __math_divzero __math_invalid \
   __rem_pio2 __rem_pio2_large __sin __cos __tan \
   stubs
@@ -158,7 +158,11 @@ _build/wasm/musl_%.o: %.c | _build/wasm
 
 .PHONY: _build/wasm/libmotoko_rts.a
 _build/wasm/libmotoko_rts.a: | _build/wasm
-	cd motoko-rts && cargo build --target=wasm32-unknown-emscripten --release
+	# NB. codegen-units=1 is to make debugging easier, not strictly
+	# necessary
+	cd motoko-rts && \
+	    xargo rustc --target=wasm32-unknown-emscripten --release -- \
+		-Crelocation-model=pic -Ccodegen-units=1
 	cp motoko-rts/target/wasm32-unknown-emscripten/release/libmotoko_rts.a $@
 
 .PHONY: _build/native/libmotoko_rts.a
@@ -179,6 +183,7 @@ mo-rts.wasm: $(RTS_WASM_O) $(RTS_RUST_WASM_O) $(TOMMATH_WASM_O) $(MUSL_WASM_O)
 	$(WASM_LD) -o $@ \
 		--import-memory --shared --no-entry --gc-sections \
 		--export=__wasm_call_ctors \
+		--whole-archive \
 		$+
 
 #

rts/motoko-rts/.cargo/config

@@ -0,0 +1,4 @@
+# NB. codegen-units=1 is not necessary, but it generates less .o files for core,
+# std, and compiler_builtins and makes it easier to find symbols.
+[build]
+rustflags = ["-Crelocation-model=pic", "-Ccodegen-units=1"]

rts/motoko-rts/Cargo.lock

@@ -4,6 +4,9 @@ version = "0.1.0"
 authors = ["Ömer Sinan Ağacan <[email protected]>"]
 edition = "2018"
 
+[dependencies]
+libc = "0.2.73"
+
 [lib]
 crate-type = ["staticlib"]
 

rts/motoko-rts/Cargo.toml

@@ -2,6 +2,7 @@ extern "C" {
     pub fn rts_trap_with(msg: *const u8) -> !;
 }
 
+/*
 #[cfg(target_arch = "wasm32")]
 mod ic0 {
     // NB: The #[link(...)] line below really needs to be before `extern "C"` part, we can't move
@@ -12,46 +13,10 @@ mod ic0 {
         pub fn debug_print(msg: *const u8, len: u32);
     }
 }
+*/
 
 #[cfg(target_arch = "wasm32")]
 pub unsafe fn debug_print(s: &str) {
-    ic0::debug_print(s.as_ptr(), s.len() as u32)
-}
-
-pub struct Wrapper<'a> {
-    buf: &'a mut [u8],
-    offset: usize,
-}
-
-impl<'a> Wrapper<'a> {
-    pub fn new(buf: &'a mut [u8]) -> Self {
-        Wrapper {
-            buf: buf,
-            offset: 0,
-        }
-    }
-}
-
-use core::fmt;
-
-impl<'a> fmt::Write for Wrapper<'a> {
-    fn write_str(&mut self, s: &str) -> fmt::Result {
-        let bytes = s.as_bytes();
-
-        // Skip over already-copied data
-        let remainder = &mut self.buf[self.offset..];
-        // Check if there is space remaining (return error instead of panicking)
-        if remainder.len() < bytes.len() {
-            return Err(core::fmt::Error);
-        }
-        // Make the two slices the same length
-        let remainder = &mut remainder[..bytes.len()];
-        // Copy
-        remainder.copy_from_slice(bytes);
-
-        // Update offset to avoid overwriting
-        self.offset += bytes.len();
-
-        Ok(())
-    }
+    // ic0::debug_print(s.as_ptr(), s.len() as u32)
+    libc::printf("%s\n".as_ptr() as *const _, s);
 }

rts/motoko-rts/src/common.rs

@@ -6,10 +6,9 @@
 // TODO: inconsistent use of size vs. len
 
 use core::arch::wasm32;
-use core::fmt::Write;
 
 use crate::array::array_idx_unchecked;
-use crate::common::{debug_print, rts_trap_with, Wrapper};
+use crate::common::{debug_print, rts_trap_with};
 use crate::types::*;
 
 extern "C" {
@@ -427,12 +426,12 @@ pub unsafe extern "C" fn rust_collect_garbage() {
     debug_print("### Evacuating roots");
 
     let mut buf = [0 as u8; 100];
-    let _ = write!(
-        Wrapper::new(&mut buf),
-        "### begin_from_space={}",
+    libc::snprintf(
+        buf.as_mut_ptr() as *mut _,
+        100,
+        "### begin_from_space=%d".as_ptr() as *const _,
         begin_from_space.unskew()
     );
-    
 
     // Evacuate roots
     end_to_space = evac_static_roots(begin_from_space, begin_to_space, end_to_space, static_roots);