build(rust): select archives by target and HUF mode

Derive the Rust static-library configuration from the effective C HUF decoder
flags and place each mode in its own Cargo target directory. This prevents a
forced X1/X2 C build from silently reusing the default Rust archive.

The test and program makefiles now also build and link an i686 Rust archive
for their 32-bit targets, including zstd32. zstd-small retains its existing
default configuration while preserving an explicitly requested HUF mode.

Test Plan:
- cargo clippy; cargo clippy --benches; cargo clippy --tests
- cargo +nightly fmt, then repeat the Clippy checks
- cargo test --all-targets for default, forced X1, and forced X2 modes
- cargo build --release --target i686-unknown-linux-gnu for each mode
- make -n checks for default, forced, direct -D, and 32-bit test/CLI targets

Refs: rust/README.md

programs/Makefile

@@ -27,12 +27,55 @@ include $(LIBZSTD_MK_DIR)/libzstd.mk
 CARGO ?= cargo
 RUST_DIR := ../rust
 RUST_MANIFEST := $(RUST_DIR)/Cargo.toml
-RUST_STATICLIB := $(RUST_DIR)/target/release/libzstd_rs.a
 RUST_SOURCES := $(RUST_MANIFEST) $(RUST_DIR)/Cargo.lock \
                 $(shell find $(RUST_DIR)/src -type f -name '*.rs' -print)
 
+# Keep Rust's HUF implementation in lockstep with libzstd.mk's C selection.
+# Forced modes may arrive as libzstd.mk variables or as direct -D flags in
+# MOREFLAGS/CFLAGS/CPPFLAGS, as used by the C-only build matrix.
+RUST_HUF_FORCE_X1 := $(HUF_FORCE_DECOMPRESS_X1)
+RUST_HUF_FORCE_X2 := $(HUF_FORCE_DECOMPRESS_X2)
+ifneq ($(filter -DHUF_FORCE_DECOMPRESS_X1 -DHUF_FORCE_DECOMPRESS_X1=%,$(CPPFLAGS) $(CFLAGS) $(MOREFLAGS)),)
+RUST_HUF_FORCE_X1 := 1
+endif
+ifneq ($(filter -DHUF_FORCE_DECOMPRESS_X2 -DHUF_FORCE_DECOMPRESS_X2=%,$(CPPFLAGS) $(CFLAGS) $(MOREFLAGS)),)
+RUST_HUF_FORCE_X2 := 1
+endif
+
+# A separate target directory per mode prevents a forced build from reusing the
+# default archive, and also gives link targets a configuration-specific input.
+ifneq ($(RUST_HUF_FORCE_X1),0)
+ifneq ($(RUST_HUF_FORCE_X2),0)
+$(error HUF_FORCE_DECOMPRESS_X1 and HUF_FORCE_DECOMPRESS_X2 are mutually exclusive)
+endif
+endif
+
+RUST_HUF_FEATURE :=
+RUST_BUILD_CONFIG := default
+ifneq ($(RUST_HUF_FORCE_X1),0)
+RUST_HUF_FEATURE := huf-force-decompress-x1
+RUST_BUILD_CONFIG := huf-force-decompress-x1
+endif
+ifneq ($(RUST_HUF_FORCE_X2),0)
+RUST_HUF_FEATURE := huf-force-decompress-x2
+RUST_BUILD_CONFIG := huf-force-decompress-x2
+endif
+
+RUST_TARGET_DIR := $(RUST_DIR)/target/$(RUST_BUILD_CONFIG)
+RUST_STATICLIB := $(RUST_TARGET_DIR)/release/libzstd_rs.a
+RUST_TARGET_32 ?= i686-unknown-linux-gnu
+RUST_STATICLIB_32 := $(RUST_TARGET_DIR)/$(RUST_TARGET_32)/release/libzstd_rs.a
+RUST_CARGO_FLAGS := --manifest-path $(RUST_MANIFEST) --release \
+                    --target-dir $(RUST_TARGET_DIR)
+ifneq ($(RUST_HUF_FEATURE),)
+RUST_CARGO_FLAGS += --features $(RUST_HUF_FEATURE)
+endif
+
 $(RUST_STATICLIB): $(RUST_SOURCES)
-	$(CARGO) build --manifest-path $(RUST_MANIFEST) --release
+	$(CARGO) build $(RUST_CARGO_FLAGS)
+
+$(RUST_STATICLIB_32): $(RUST_SOURCES)
+	$(CARGO) build $(RUST_CARGO_FLAGS) --target $(RUST_TARGET_32)
 
 ifeq ($(shell $(CC) -v 2>&1 | $(GREP) -c "gcc version "), 1)
   ALIGN_LOOP = -falign-loops=32
@@ -205,7 +248,7 @@ zstd32 : CPPFLAGS += -DZSTD_LEGACY_SUPPORT=$(ZSTD_LEGACY_SUPPORT)
 ifneq (,$(filter Windows%,$(OS)))
 zstd32 : $(RES32_FILE)
 endif
-zstd32 : $(ZSTDLIB_FULL_SRC) $(ZSTD_CLI_SRC)
+zstd32 : $(ZSTDLIB_FULL_SRC) $(ZSTD_CLI_SRC) $(RUST_STATICLIB_32)
 	$(CC) -m32 $(FLAGS) $^ -o $@$(EXT)
 
 ## zstd-nolegacy: same scope as zstd, with removed support of legacy formats
@@ -265,7 +308,10 @@ endif
 
 ## zstd-small: minimal target, supporting only zstd compression and decompression. no bench. no legacy. no other format.
 CLEAN += zstd-small zstd-frugal
-zstd-small: CFLAGS = -Os -Wl,-s
+# The target-specific CFLAGS assignment would otherwise hide an explicitly
+# requested HUF decoder mode from the C sources while the Rust archive sees it.
+ZSTD_SMALL_HUF_CFLAGS := $(filter -DHUF_FORCE_DECOMPRESS_X1% -DHUF_FORCE_DECOMPRESS_X2%,$(CFLAGS))
+zstd-small: CFLAGS = -Os -Wl,-s $(ZSTD_SMALL_HUF_CFLAGS)
 zstd-frugal zstd-small: $(ZSTDLIB_CORE_SRC) zstdcli.c util.c timefn.c fileio.c fileio_asyncio.c $(RUST_STATICLIB)
 	$(CC) $(FLAGS) -DZSTD_NOBENCH -DZSTD_NODICT -DZSTD_NOTRACE -UZSTD_LEGACY_SUPPORT -DZSTD_LEGACY_SUPPORT=0 $^ -o $@$(EXT)
 

rust/Cargo.toml

@@ -6,5 +6,10 @@ edition = "2021"
 [lib]
 crate-type = ["staticlib"]
 
+[features]
+default = []
+huf-force-decompress-x1 = []
+huf-force-decompress-x2 = []
+
 [dependencies]
 libc = "0.2"

rust/README.md

@@ -41,10 +41,11 @@ source file whose implementation has moved to Rust remains in the original
 makefile source list as a small shim so header configuration and platform
 preprocessor behavior stay available during the transition.
 
-The test and program makefiles make `target/release/libzstd_rs.a` a normal
+The test and program makefiles select an archive directory for the active C
-link prerequisite. They rebuild the Rust archive and relink the executable
+configuration: default, forced HUF X1/X2, and the matching Rust target for
-when a Rust source changes, so original C tests do not accidentally use a stale
+32-bit C binaries. They rebuild the selected archive and relink the executable
-implementation.
+when a Rust source changes, so original C tests do not accidentally use a
+stale or configuration-incompatible implementation.
 
 ## Validation
 

tests/Makefile

@@ -41,12 +41,55 @@ TESTARTEFACT := versionsTest
 CARGO ?= cargo
 RUST_DIR := ../rust
 RUST_MANIFEST := $(RUST_DIR)/Cargo.toml
-RUST_STATICLIB := $(RUST_DIR)/target/release/libzstd_rs.a
 RUST_SOURCES := $(RUST_MANIFEST) $(RUST_DIR)/Cargo.lock \
                 $(shell find $(RUST_DIR)/src -type f -name '*.rs' -print)
 
+# Keep Rust's HUF implementation in lockstep with libzstd.mk's C selection.
+# Forced modes may arrive as libzstd.mk variables or as direct -D flags in
+# MOREFLAGS/CFLAGS/CPPFLAGS, as used by the C-only build matrix.
+RUST_HUF_FORCE_X1 := $(HUF_FORCE_DECOMPRESS_X1)
+RUST_HUF_FORCE_X2 := $(HUF_FORCE_DECOMPRESS_X2)
+ifneq ($(filter -DHUF_FORCE_DECOMPRESS_X1 -DHUF_FORCE_DECOMPRESS_X1=%,$(CPPFLAGS) $(CFLAGS) $(MOREFLAGS)),)
+RUST_HUF_FORCE_X1 := 1
+endif
+ifneq ($(filter -DHUF_FORCE_DECOMPRESS_X2 -DHUF_FORCE_DECOMPRESS_X2=%,$(CPPFLAGS) $(CFLAGS) $(MOREFLAGS)),)
+RUST_HUF_FORCE_X2 := 1
+endif
+
+# A separate target directory per mode prevents a forced build from reusing the
+# default archive, and also gives link targets a configuration-specific input.
+ifneq ($(RUST_HUF_FORCE_X1),0)
+ifneq ($(RUST_HUF_FORCE_X2),0)
+$(error HUF_FORCE_DECOMPRESS_X1 and HUF_FORCE_DECOMPRESS_X2 are mutually exclusive)
+endif
+endif
+
+RUST_HUF_FEATURE :=
+RUST_BUILD_CONFIG := default
+ifneq ($(RUST_HUF_FORCE_X1),0)
+RUST_HUF_FEATURE := huf-force-decompress-x1
+RUST_BUILD_CONFIG := huf-force-decompress-x1
+endif
+ifneq ($(RUST_HUF_FORCE_X2),0)
+RUST_HUF_FEATURE := huf-force-decompress-x2
+RUST_BUILD_CONFIG := huf-force-decompress-x2
+endif
+
+RUST_TARGET_DIR := $(RUST_DIR)/target/$(RUST_BUILD_CONFIG)
+RUST_STATICLIB := $(RUST_TARGET_DIR)/release/libzstd_rs.a
+RUST_TARGET_32 ?= i686-unknown-linux-gnu
+RUST_STATICLIB_32 := $(RUST_TARGET_DIR)/$(RUST_TARGET_32)/release/libzstd_rs.a
+RUST_CARGO_FLAGS := --manifest-path $(RUST_MANIFEST) --release \
+                    --target-dir $(RUST_TARGET_DIR)
+ifneq ($(RUST_HUF_FEATURE),)
+RUST_CARGO_FLAGS += --features $(RUST_HUF_FEATURE)
+endif
+
 $(RUST_STATICLIB): $(RUST_SOURCES)
-	$(CARGO) build --manifest-path $(RUST_MANIFEST) --release
+	$(CARGO) build $(RUST_CARGO_FLAGS)
+
+$(RUST_STATICLIB_32): $(RUST_SOURCES)
+	$(CARGO) build $(RUST_CARGO_FLAGS) --target $(RUST_TARGET_32)
 
 DEBUGFLAGS += -g -Wno-c++-compat
 CPPFLAGS   += -I$(LIB_SRCDIR) -I$(LIB_SRCDIR)/common -I$(LIB_SRCDIR)/compress -I$(LIB_SRCDIR)/legacy \
@@ -259,12 +302,15 @@ poolTests : $(PRGDIR)/util.c $(PRGDIR)/timefn.c poolTests.c $(LIB_SRCDIR)/common
 # These static C test executables exercise Rust replacements. The normal
 # prerequisite is also an archive input, placed after C sources by `$^`, and
 # rebuilding Rust therefore relinks rather than leaving a stale implementation.
-RUST_LINK_TARGETS := $(FULLBENCHS) fuzzer fuzzer32 zstreamtest zstreamtest32 \
+RUST_LINK_TARGETS := fullbench fuzzer zstreamtest \
                      zstreamtest_asan zstreamtest_tsan zstreamtest_ubsan \
                      paramgrill roundTripCrash longmatch largeDictionary \
                      invalidDictionaries legacy decodecorpus poolTests
 $(RUST_LINK_TARGETS): $(RUST_STATICLIB)
 
+RUST_LINK_TARGETS_32 := fullbench32 fuzzer32 zstreamtest32
+$(RUST_LINK_TARGETS_32): $(RUST_STATICLIB_32)
+
 .PHONY: versionsTest
 versionsTest: clean
 	$(PYTHON) test-zstd-versions.py