From: Tim Chevalier <tjc@igalia.com>
Date: Tue, 29 Jul 2025 14:14:27 -0700
Subject: Fix build and tests for wasm32-wasip2 target (#599)

Trying to build wasi-libc for the `wasm32-wasip2` target and run the
tests, I noticed a few issues:

- `TARGET_TRIPLE` was being used before definition, in the definition of
`OBJDIR`.
- The ?= operator instead of = was being used to set `TARGET_TRIPLE` to
`wasm32-wasip2`.
This always left the target as `wasm32-wasi`, since it was defined to
that in a previous line.
- `builtins` wasn't being built by default, so building the tests would
fail because it was unable to find `libclang_rt.builtins.a`.
- `make test` didn't take the`WASI_SNAPSHOT` variable into
consideration.
- When building tests, `clang --target=wasm32-wasip2` was building a P2
component,
which caused the subsequent `wasm-tools component new` to fail because
the input
was already a component.

This PR fixes these issues. Now I'm able to run the tests with
`WASI_SNAPSHOT=p2`.

(cherry picked from commit 93bd1f6048b163ca9b12336a4758a6f5c11c908c)
---
 Makefile      | 38 ++++++++++++++++++++++----------------
 test/Makefile | 16 ++++++++++++++++
 2 files changed, 38 insertions(+), 16 deletions(-)

diff --git a/Makefile b/Makefile
index 8b90bbf..61b4046 100644
--- a/Makefile
+++ b/Makefile
@@ -23,6 +23,20 @@ MALLOC_IMPL ?= dlmalloc
 BUILD_LIBC_TOP_HALF ?= yes
 # yes or no
 BUILD_LIBSETJMP ?= yes
+
+# Set the default WASI target triple.
+TARGET_TRIPLE ?= wasm32-wasi
+
+# Threaded version necessitates a different target, as objects from different
+# targets can't be mixed together while linking.
+ifeq ($(THREAD_MODEL), posix)
+TARGET_TRIPLE = wasm32-wasip1-threads
+endif
+
+ifeq ($(WASI_SNAPSHOT), p2)
+TARGET_TRIPLE = wasm32-wasip2
+endif
+
 # The directory where we will store intermediate artifacts.
 OBJDIR ?= build/$(TARGET_TRIPLE)
 
@@ -46,19 +60,6 @@ BULK_MEMORY_THRESHOLD ?= 32
 # Variables from this point on are not meant to be overridable via the
 # make command-line.
 
-# Set the default WASI target triple.
-TARGET_TRIPLE ?= wasm32-wasi
-
-# Threaded version necessitates a different target, as objects from different
-# targets can't be mixed together while linking.
-ifeq ($(THREAD_MODEL), posix)
-TARGET_TRIPLE ?= wasm32-wasi-threads
-endif
-
-ifeq ($(WASI_SNAPSHOT), p2)
-TARGET_TRIPLE ?= wasm32-wasip2
-endif
-
 # These artifacts are "stamps" that we use to mark that some task (e.g., copying
 # files) has been completed.
 INCLUDE_DIRS := $(OBJDIR)/copy-include-headers.stamp
@@ -597,7 +598,9 @@ PIC_OBJS = \
 # exists that should be used instead.
 SYSTEM_BUILTINS_LIB := $(shell ${CC} ${CFLAGS} --print-libgcc-file-name)
 SYSTEM_RESOURCE_DIR := $(shell ${CC} ${CFLAGS} -print-resource-dir)
-BUILTINS_LIB_REL := $(subst $(SYSTEM_RESOURCE_DIR),,$(SYSTEM_BUILTINS_LIB))
+BUILTINS_LIB_REL_1 := $(subst $(SYSTEM_RESOURCE_DIR),,$(SYSTEM_BUILTINS_LIB))
+# Substitute '/' for '\' so Windows paths work
+BUILTINS_LIB_REL := $(subst \,/,$(BUILTINS_LIB_REL_1))
 TMP_RESOURCE_DIR := $(OBJDIR)/resource-dir
 BUILTINS_LIB_PATH := $(TMP_RESOURCE_DIR)/$(BUILTINS_LIB_REL)
 BUILTINS_LIB_DIR := $(dir $(BUILTINS_LIB_PATH))
@@ -611,7 +614,10 @@ else
 BUILTINS_URL := https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-25/libclang_rt.builtins-wasm32-wasi-25.0.tar.gz
 
 $(BUILTINS_LIB_PATH):
-	mkdir -p $(BUILTINS_LIB_DIR)
+# mkdir on Windows will error if the directory already exists
+ifeq ("$(wildcard $(BUILTINS_LIB_DIR))","")
+	mkdir -p "$(BUILTINS_LIB_DIR)"
+endif
 	curl -sSfL $(BUILTINS_URL) | \
 		tar xzf - -C $(BUILTINS_LIB_DIR) --strip-components 1
 	if [ ! -f $(BUILTINS_LIB_PATH) ]; then \
@@ -853,7 +859,7 @@ STATIC_LIBS += \
 	$(SYSROOT_LIB)/libsetjmp.a
 endif
 
-libc: $(INCLUDE_DIRS) $(STATIC_LIBS)
+libc: $(INCLUDE_DIRS) $(STATIC_LIBS) builtins
 	touch $@
 
 DUMMY := m rt pthread crypt util xnet resolv
diff --git a/test/Makefile b/test/Makefile
index 4aff0ab..b84ebf3 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -14,6 +14,15 @@ test: run
 # Decide which target to build for and which libc to use.
 TARGET_TRIPLE ?= wasm32-wasi
 
+# See comment in ../Makefile
+ifeq ($(THREAD_MODEL), posix)
+TARGET_TRIPLE = wasm32-wasip1-threads
+endif
+
+ifeq ($(WASI_SNAPSHOT), p2)
+TARGET_TRIPLE = wasm32-wasip2
+endif
+
 # Setup various paths used by the tests.
 OBJDIR ?= build/$(TARGET_TRIPLE)
 DOWNDIR ?= build/download
@@ -135,6 +144,13 @@ $(BUILTINS_STAMP):
 	make -C .. builtins
 	touch $@
 
+# For wasip2, we want clang to generate a core module rather than a component,
+# because `wasm-tools component new` is called subsequently and it expects
+# a core module.
+ifeq ($(TARGET_TRIPLE), wasm32-wasip2)
+LDFLAGS += -Wl,--skip-wit-component
+endif
+
 # Build up all the `*.wasm.o` object files; these are the same regardless of
 # whether we're building core modules or components.
 $(WASM_OBJS): $(INFRA_HEADERS)