mrustc: init

This bootstraps rustc via the mrustc alternative compiler. The build
process is extraordinarily ugly because rustc maintainers cargo culted
target triple strings without understanding what they are, and
completely mishandles them. They also appear to lack fundamental system
understanding and assume musl can only be used for static linking. The
build process also fails to populate their so called self-contained
library directory, so it is manually put together here.

This setup uses the vendored LLVM for multiple reasons: the fact that
rustc maintainers manage to fuck up so badly they simultaneously pass
GCC-only and Clang-only flags when using an LLVM configured to use
libc++ instead of GNU slop, and the immense maintenance burden to keep
this up to date enough to use Rosa OS LLVM. For now, time and effort
saved from trying to mutilate this pile of garbage into working with a
proper LLVM build more than compensates for the wasted CPU time.

GCC libraries are included in the output because despite the utter
reluctance to do dynamic linking correctly on musl, it seems that rustc
is also incapable of passing the correct linker flags to produce static
executables, and the miserable mrustc Makefiles make it impossible to
specify custom linker flags. From my previous experience producing a
static virtiofsd build, it would require multiple arguments per library,
all of them in rustc's fucked up custom syntax, and I am not ready to
deal with that. To avoid contaminating future stages with gcc, this
package includes only libraries required at runtime.

Signed-off-by: Ophestra <cat@gensokyo.uk>

mrustc/0001-do-not-download-rustc.patch

@@ -1,7 +1,7 @@
 From 157772049aa7da13533026292cb4f67c1e8bf542 Mon Sep 17 00:00:00 2001
 From: nobody <nobody@localhost>
 Date: Sun, 19 Jul 2026 06:21:49 +0900
-Subject: [PATCH 1/2] do not download rustc
+Subject: [PATCH 1/3] do not download rustc
 
 The $(RUSTC_SRC_DL) file already exists, but for some reason Make wants
 to rebuild this target when it has $(RUSTC_SRC_TARBALL) as a dependency.

mrustc/0002-Revert-HIR-Typecheck-Optimise-by-doing-multiple-chec.patch

@@ -1,7 +1,7 @@
 From 6e66feb3b6ae698c3d29211847c71c00f87fbf78 Mon Sep 17 00:00:00 2001
 From: nobody <nobody@localhost>
 Date: Sun, 19 Jul 2026 06:23:12 +0900
-Subject: [PATCH 2/2] Revert "HIR Typecheck - Optimise by doing multiple checks
+Subject: [PATCH 2/3] Revert "HIR Typecheck - Optimise by doing multiple checks
  per pass"
 
 This reverts commit 99d9bd0c788b0c72fc2f4fee6187a462ceb059f2.

mrustc/b00-link-self-contained.patch

@@ -0,0 +1,54 @@
+diff --git a/run_rustc/Makefile b/run_rustc/Makefile
+index e78d8c51..cc9f785e 100644
+--- a/run_rustc/Makefile
++++ b/run_rustc/Makefile
+@@ -150,14 +150,23 @@ $(CARGO_HOME)config: Makefile
+ 	$Vecho "[source.vendored-sources]" >> $@
+ 	$Vecho "directory = \"$(abspath $(VENDOR_DIR))\"" >> $@
+ 
++self-contained:
++	mkdir -p $@
++	(set -o braceexpand && ln -s \
++		/system/lib/{'rcrt1.o','crti.o','crtn.o'} \
++		/system/lib/gcc/"$(ROSA_TRIPLE)"/"$(shell gcc -dumpfullversion)"/{'crtbeginS.o','crtendS.o'} \
++		/system/lib/"$(ROSA_TRIPLE)"/* \
++		$@)
++
+ # -------------------------------------
+ # Stage 1: Build standard library (using minicargo with rustc)
+ # - Can't use `cargo` because there isn't a rustc-compatible std yet
+ # - _could_ use it if mrustc accepted all the arguments rustc does (via the proxy)
+ # -------------------------------------
+-$(LIBDIR_S)libstd.rlib: $(BINDIR_S)rustc $(MINICARGO) Makefile
++$(LIBDIR_S)libstd.rlib: self-contained $(BINDIR_S)rustc $(MINICARGO) Makefile
+ 	@echo "[MINICARGO] $(RUST_SRC_LIBS)std > $(LIBDIR_S)"
+-	mkdir -p $(LIBDIR_S)
++	@mkdir -p $(LIBDIR_S)
++	@ln -sf ../../../../../../self-contained $(LIBDIR_S)
+ ifneq ($(TARGETVER_LEAST_1_74),)
+ 	$V+STD_ENV_ARCH=$(RUSTC_ARCH) MRUSTC_PATH=$(abspath $(BINDIR_S)rustc) $(MINICARGO) --vendor-dir $(VENDOR_DIR) --script-overrides ../script-overrides/stable-$(RUSTC_VERSION)-$(PLATFORM)/ --output-dir $(LIBDIR_S) $(RUST_SRC_LIBS)sysroot
+ else
+@@ -178,6 +187,7 @@ CARGO_OUTDIR_STAGE2_STD := $(OUTDIR)build-std2/$(RUSTC_TARGET)/release/
+ CARGO_ENV_STAGE2_STD := CARGO_TARGET_DIR=$(OUTDIR)build-std2 RUSTC=$(abspath rustc_proxy.sh) PROXY_RUSTC=$(abspath $(BINDIR_2)rustc) PROXY_MRUSTC=$(abspath $(BINDIR_S)rustc) $(CARGO_ENV)
+ $(LIBDIR_2)libtest.rlib: $(LIBDIR_S)libstd.rlib $(BINDIR_2)rustc $(BINDIR_S)rustc $(BINDIR_S)cargo $(CARGO_HOME)config Makefile
+ 	@mkdir -p $(LIBDIR_2)
++	@ln -sf ../../../../../../self-contained $(LIBDIR_2)
+ 	@echo [CARGO] $(RUST_SRC_LIBS)test/Cargo.toml '>' $(OUTDIR)build-std2
+ ifneq ($(TARGETVER_LEAST_1_74),)
+ 	$V$(CARGO_ENV_STAGE2_STD) $(BINDIR_S)cargo build $(CARGO_FLAGS) --manifest-path $(RUST_SRC_LIBS)sysroot/Cargo.toml --features panic-unwind
+@@ -215,6 +225,7 @@ else
+ 	@echo "[CP] libraries and results ($@)"
+ endif
+ 	@mkdir -p $(LIBDIR)
++	@ln -sf ../../../../../../self-contained $(LIBDIR)
+ 	$Vcp $(LIBDIR_2)*.$(DYLIB_EXT) $(PREFIX)lib
+ 	$Vcp $(CARGO_OUTDIR_RUSTC)deps/*.rlib $(LIBDIR)
+ 	$Vcp $(CARGO_OUTDIR_RUSTC)deps/*.$(DYLIB_EXT) $(LIBDIR)
+@@ -243,6 +254,7 @@ CARGO_OUTDIR_STAGE3_STD := $(OUTDIR)build-std/$(RUSTC_TARGET)/release/
+ CARGO_ENV_STAGE3_STD := CARGO_TARGET_DIR=$(OUTDIR)build-std RUSTC=$(abspath rustc_proxy.sh) PROXY_RUSTC=$(abspath $(BINDIR)rustc) PROXY_MRUSTC=$(abspath $(BINDIR_2)rustc) $(CARGO_ENV)
+ $(LIBDIR)libstd.rlib: $(BINDIR)rustc
+ 	@mkdir -p $(LIBDIR)
++	@ln -sf ../../../../../../self-contained $(LIBDIR)
+ 	@echo [CARGO] $(RUST_SRC_LIBS)test/Cargo.toml '>' $(OUTDIR)build-std2
+ ifneq ($(TARGETVER_LEAST_1_74),)
+ 	$V$(CARGO_ENV_STAGE3_STD) $(BINDIR_S)cargo build $(CARGO_FLAGS) --manifest-path $(RUST_SRC_LIBS)sysroot/Cargo.toml --features panic-unwind

mrustc/package.az

@@ -12,6 +12,7 @@ package mrustc-source {
 	patches = [
 		"0001-do-not-download-rustc.patch",
 		"0002-Revert-HIR-Typecheck-Optimise-by-doing-multiple-chec.patch",
+		"0003-rustc-src-enable-rustix-use-libc-feature-revert-port.patch",
 
 		"remove-git-invocations.patch",
 	];
@@ -47,7 +48,7 @@ package mrustc {
 }
 
 package rustc-bootstrap-source {
-	description = "rustc source tree used by mrustc";
+	description = "unpatched bootstrap rust toolchain source tree";
 	exclude = true;
 
 	version# = "1.90.0";
@@ -59,63 +60,164 @@ package rustc-bootstrap-source {
 	chmod = true;
 }
 
-package rustc-bootstrap {
+package rustc-bootstrap-llvm {
-	description = "rust toolchain bootstrapped via mrustc";
+	description = "bootstrap rustc-standalone LLVM build";
 	exclude = true;
 
-	source = mrustc-source;
+	source = rustc-bootstrap-source;
-	extra = [ rustc-bootstrap-source ];
+	exec = cmake {
+		append = [ "src", "llvm-project", "llvm" ];
+
+		// Reference $(RUSTCSRC)src/bootstrap/native.rs for these values
+		cache = {
+			"CMAKE_C_COMPILER": "gcc";
+			"CMAKE_C_FLAGS": "-w";
+			"CMAKE_CXX_COMPILER": "g++";
+			"CMAKE_CXX_FLAGS": "-w";
+			"LLVM_LINK_LLVM_DYLIB": "OFF";
+			"LLVM_TARGETS_TO_BUILD": "'X86;ARM;AArch64'";
+			"LLVM_ENABLE_ASSERTIONS": "OFF";
+			"LLVM_INCLUDE_EXAMPLES": "OFF";
+			"LLVM_INCLUDE_TESTS": "OFF";
+			"LLVM_INCLUDE_DOCS": "OFF";
+			"LLVM_INCLUDE_BENCHMARKS": "OFF";
+			"LLVM_ENABLE_ZLIB": "OFF";
+			"LLVM_ENABLE_TERMINFO": "OFF";
+			"LLVM_ENABLE_LIBEDIT": "OFF";
+			"WITH_POLLY": "OFF";
+			"LIBUNWIND_ENABLE_SHARED": "OFF";
+		};
+		skipTest = true;
+	};
+
+	inputs = [
+		python-early,
+
+		gcc,
+		kernel-headers,
+	];
+}
+
+package rustc-mrustc {
+	description = "initial rustc stage compiled by mrustc";
+	exclude = true;
+
+	source = rustc-bootstrap-source;
+	extra = [
+		mrustc-source,
+		rustc-bootstrap-llvm,
+	];
 
-	enterSource = true;
 	writable = true;
+	early = "cd ../extra/mrustc-source";
+	minimal = true;
 
 	exec = make {
 		inPlace = true;
 		skipConfigure = true;
 		preMake = `
+LLVM='../rustc-bootstrap-llvm/system/bin/llvm-config'
+RUSTC_SOURCE='../../rustc-mrustc'
+
+export CC=gcc CXX=g++
 export PARLEVEL=`+jobsE+`
-export RUSTC_SOURCE='../extra/rustc-bootstrap-source'
+export RUSTC_TARGET="$(uname -m)-unknown-linux-musl"
 export RUSTC_VERSION="$(cut -d ' ' -f 1 "$RUSTC_SOURCE/version")"
 export MRUSTC_TARGET_VER="$(cut -d '.' -f 1,2 <<< "$RUSTC_VERSION")"
 export OUTDIR_SUF="-$RUSTC_VERSION"
+
 patch -d "$RUSTC_SOURCE" -p0 < "rustc-$RUSTC_VERSION-src.patch"
 touch "$RUSTC_SOURCE/dl-version"
 
 ln -s "$RUSTC_SOURCE" "rustc-$RUSTC_VERSION-src"
 mkdir bin && ln -s /system/bin/mrustc bin/
+ln -sf gcc /system/bin/cc
+ln -sf g++ /system/bin/c++
 `;
 		make = [
 			"-f",
 			"minicargo.mk",
-			"CC=gcc",
 			"CXX='g++ -w'",
+			`LLVM_CONFIG="$LLVM"`,
 			"LIBS",
 		];
 		check = [
-			"CC=gcc",
 			"CXX='g++ -w'",
-			"test",
+			// run this first to avoid intermittent failures
 			"local_tests",
 		];
 
 		install = `
-export CC=gcc CXX=g++
+make \
+	`+jobsFlagE+` \
+	`+loadFlagE+` \
+	CXX='g++ -w' \
+	test
+
 OUTDIR="output-$RUSTC_VERSION"
-make -f minicargo.mk "$OUTDIR/rustc"
+make -f minicargo.mk LLVM_CONFIG="$LLVM" "$OUTDIR/rustc"
-make -f minicargo.mk "$OUTDIR/cargo"
+make -f minicargo.mk LLVM_CONFIG="$LLVM" "$OUTDIR/cargo"
-make -C run_rustc
+mkdir -p /work/system/bin/
+(set -o braceexpand && cp "$OUTDIR"/{rustc,cargo} bin/minicargo /work/system/bin/)
 `;
 	};
 
 	inputs = [
 		bash,
-		patch,
-		cmake,
-		pkg-config,
 		perl,
-		python,
+		patch,
 		mrustc,
+		llvm,
+	];
 
-		kernel-headers,
+	runtime = [ gcc, llvm, mrustc ];
+}
+
+package rustc-bootstrap {
+	description = "early rustc bootstrapped by rustc-mrustc";
+	exclude = true;
+
+	source = rustc-bootstrap-source;
+	extra = [ mrustc-source ];
+	files = {
+		"b00-link-self-contained.patch";
+	};
+
+	writable = true;
+	early = "cd ../extra/mrustc-source";
+	minimal = true;
+
+	exec = make {
+		inPlace = true;
+		skipConfigure = true;
+		preMake = `
+RUSTC_SOURCE='../../rustc-bootstrap'
+
+export RUSTC_TARGET="$(uname -m)-unknown-linux-musl"
+export RUSTC_VERSION="$(cut -d ' ' -f 1 "$RUSTC_SOURCE/version")"
+
+patch -d "$RUSTC_SOURCE" -p0 < "rustc-$RUSTC_VERSION-src.patch"
+cat /usr/src/*.patch | patch -p1
+
+ln -s "$RUSTC_SOURCE" "rustc-$RUSTC_VERSION-src"
+mkdir bin "output-$RUSTC_VERSION"
+(set -o braceexpand && \
+	ln -s /system/bin/{mrustc,minicargo} bin/ && \
+	ln -s /system/bin/{rustc,cargo} "output-$RUSTC_VERSION")
+ln -sf gcc /system/bin/cc
+ln -sf g++ /system/bin/c++
+`;
+		make = [
+			"-C", "run_rustc",
+			"CC=gcc",
+			"PARLEVEL="+jobsE,
+		];
+	};
+
+	inputs = [
+		bash,
+		patch,
+
+		rustc-mrustc,
 	];
 }

mrustc/remove-git-invocations.patch

@@ -1,13 +1,13 @@
 diff --git a/Makefile b/Makefile
-index 4317d2c0..415427b4 100644
+index bb8e64a4..6bc951a7 100644
 --- a/Makefile
 +++ b/Makefile
-@@ -187,7 +187,7 @@ $(OBJDIR)%.o: src/%.cpp
+@@ -188,7 +188,7 @@ $(OBJDIR)%.o: src/%.cpp
  $(OBJDIR)version.o: $(OBJDIR)%.o: src/%.cpp $(filter-out $(OBJDIR)version.o,$(OBJ)) Makefile
  	@+mkdir -p $(dir $@)
  	@echo [CXX] -o $@
 -	$V$(CXX) -o $@ -c $< $(CXXFLAGS) $(CPPFLAGS) -MMD -MP -MF $@.dep -D VERSION_GIT_FULLHASH=\"$(shell git show --pretty=%H -s --no-show-signature)\" -D VERSION_GIT_BRANCH="\"$(shell git symbolic-ref -q --short HEAD || git describe --tags --exact-match)\"" -D VERSION_GIT_SHORTHASH=\"$(shell git show -s --pretty=%h --no-show-signature)\" -D VERSION_BUILDTIME="\"$(shell env LC_TIME=C date -u +"%a, %e %b %Y %T +0000")\"" -D VERSION_GIT_ISDIRTY=$(shell git diff-index --quiet HEAD; echo $$?)
-+	$V$(CXX) -o $@ -c $< $(CXXFLAGS) $(CPPFLAGS) -MMD -MP -MF $@.dep -D VERSION_GIT_FULLHASH=\"unknown\" -D VERSION_GIT_BRANCH="\"v0.12.0\"" -D VERSION_GIT_SHORTHASH=\"unknown\" -D VERSION_BUILDTIME="\"Thu,  1 Jan 1970 00:00:00 +0000\"" -D VERSION_GIT_ISDIRTY=0
++	$V$(CXX) -o $@ -c $< $(CXXFLAGS) $(CPPFLAGS) -MMD -MP -MF $@.dep -D VERSION_GIT_FULLHASH=\"unknown\" -D VERSION_GIT_BRANCH="\"v0.12.0\"" -D VERSION_GIT_SHORTHASH=\"unknown\" -D VERSION_BUILDTIME="\"Nya,  0 Jan -1 25:71:99 +2928\"" -D VERSION_GIT_ISDIRTY=0
  
  src/main.cpp: $(PCHS:%=src/%.gch)