Fix make THREAD_MODEL=posix (WebAssembly#311)

* Fixes for the THREAD_MODEL=posix build

* Fix expected symbols from previous commit

* Enable `lock` in `random.c` when threads are enabled

This uses the `_REENTRANT` definition to indicate when the `lock` should
be available.

* Disable `aio.h` when compiling for threads

In talking to @sunfishcode about `aio.h`, this functionality is not yet
a primary concern (it was already disabled in the default,
single-threaded mode). Additionally, this change adds expectation lines
for the new symbols/includes added and removed by `pthread.h`.

This change was reached by running:
```console
$ git diff --no-index expected/wasm32-wasi sysroot/share/wasm32-wasi > patch.diff
$ git apply patch.diff --reject
```

* Specify the TLS model until LLVM 15 is released

The `-ftls-model` configuration can be removed once https://reviews.llvm.org/D130053 makes its way into an upstream release.

* Rename `__wasi_libc_pthread_self` to `__wasilibc_pthread_self`

The symbol is still undefined, though.

* Add different sets of expected output based on THREAD_MODEL

* Re-add trailing whitespace to `predefined-macros.txt`

@sbc100 wanted to retain the whitespace trailing after certain
predefined macro lines. This change restores that whitespace from
upstream and re-generates the POSIX version using the following command:

```console
$ git diff --no-index expected/wasm32-wasi/posix/predefined-macros.txt sysroot/share/wasm32-wasi/predefined-macros.txt | sed 's/sysroot\/share\/wasm32-wasi/expected\/wasm32-wasi\/posix/' | git apply
```

* Protect `preopens.c` against concurrent access

* Only build thread-capable wasi-libc on latest version of Clang

* Use `thrd_sleep` from MUSL instead of aliasing `nanosleep`

* Define `pthread_setcancelstate` in `THREAD_MODEL=posix` builds

There are other options here (e.g., always define the `pthread_*`
symbols with stubs) but until we discuss that this is an intermediate
working step.

* Define a Wasm global to store `pthread_self`

* Remove `g_needs_dynamic_alloc` global

* Document the state of pthread support

* review: de-duplicate symbols based on WebAssembly#314

* review: only define `__wasilibc_cwd_{un}lock` when needed

* review: add #ifdefs to `__pthread_setcancelstate`

* review: add additional #ifdefs to `pthread_self.c`

* review: put lock definition behind #ifdef _REENTRANT

* review: remove pthread_setcancelstate.c

* review: re-fix indentation

* review: alias __clock_nanosleep in bottom half

* review: remove extra line

Co-authored-by: Sam Clegg <[email protected]>

Author: 2 people

.github/workflows/main.yml

@@ -64,6 +64,14 @@ jobs:
         name: ${{ format( 'sysroot-{0}.tgz', matrix.os) }}
         path: sysroot
 
+    - name: Build libc + threads
+      # Only build the thread-capable wasi-libc in the latest supported Clang
+      # version; the earliest version does not have all necessary builtins
+      # (e.g., `__builtin_wasm_memory_atomic_notify`).
+      if: matrix.clang_version != '10.0.0'
+      shell: bash
+      run: make -j4 THREAD_MODEL=posix
+
   # Disable the headerstest job for now, while WASI transitions from the
   # witx snapshots to wit proposals, and we have a few manual edits to the
   # generated header to make life easier for folks.

Makefile

@@ -13,7 +13,7 @@ EXTRA_CFLAGS ?= -O2 -DNDEBUG -ftls-model=local-exec -D_WASI_EMULATED_MMAN -D_WAS
 SYSROOT ?= $(CURDIR)/sysroot
 # A directory to install to for "make install".
 INSTALL_DIR ?= /usr/local
-# single or posix
+# single or posix; note that pthread support is still a work-in-progress.
 THREAD_MODEL ?= posix
 # dlmalloc or none
 MALLOC_IMPL ?= dlmalloc
@@ -167,6 +167,8 @@ LIBC_TOP_HALF_MUSL_SOURCES = \
         linux/wait4.c \
         linux/eventfd.c \
         stat/futimesat.c \
+        legacy/getpagesize.c \
+        thread/thrd_sleep.c \
     ) \
     $(filter-out %/procfdname.c %/syscall.c %/syscall_ret.c %/vdso.c %/version.c, \
                  $(wildcard $(LIBC_TOP_HALF_MUSL_SRC_DIR)/internal/*.c)) \
@@ -212,6 +214,7 @@ LIBC_TOP_HALF_MUSL_SOURCES = \
                  %/cimagf.c %/cimag.c %cimagl.c, \
                  $(wildcard $(LIBC_TOP_HALF_MUSL_SRC_DIR)/complex/*.c)) \
     $(wildcard $(LIBC_TOP_HALF_MUSL_SRC_DIR)/crypt/*.c)
+
 MUSL_PRINTSCAN_SOURCES = \
     $(LIBC_TOP_HALF_MUSL_SRC_DIR)/internal/floatscan.c \
     $(LIBC_TOP_HALF_MUSL_SRC_DIR)/stdio/vfprintf.c \
@@ -254,7 +257,9 @@ ifeq ($(THREAD_MODEL), single)
 CFLAGS += -mthread-model single
 endif
 ifeq ($(THREAD_MODEL), posix)
-CFLAGS += -mthread-model posix -pthread
+# Specify the tls-model until LLVM 15 is released (which should contain
+# https://reviews.llvm.org/D130053).
+CFLAGS += -mthread-model posix -pthread -ftls-model=local-exec
 endif
 
 # Expose the public headers to the implementation. We use `-isystem` for
@@ -373,11 +378,13 @@ MUSL_OMIT_HEADERS += \
     "netinet/if_ether.h" \
     "netinet/ether.h" \
     "sys/timerfd.h" \
-    "sys/sysmacros.h"
+    "libintl.h" \
+    "sys/sysmacros.h" \
+    "aio.h"
 
 ifeq ($(THREAD_MODEL), single)
 # Remove headers not supported in single-threaded mode.
-MUSL_OMIT_HEADERS += "aio.h" "pthread.h"
+MUSL_OMIT_HEADERS += "pthread.h"
 endif
 
 default: finish
@@ -604,7 +611,7 @@ check-symbols: startup_files libc
 
 	# Check that the computed metadata matches the expected metadata.
 	# This ignores whitespace because on Windows the output has CRLF line endings.
-	diff -wur "$(CURDIR)/expected/$(MULTIARCH_TRIPLE)" "$(SYSROOT_SHARE)"
+	diff -wur "$(CURDIR)/expected/$(MULTIARCH_TRIPLE)/$(THREAD_MODEL)" "$(SYSROOT_SHARE)"
 
 install: finish
 	mkdir -p "$(INSTALL_DIR)"

README.md

@@ -3,8 +3,12 @@
 WASI Libc is a libc for WebAssembly programs built on top of WASI system calls.
 It provides a wide array of POSIX-compatible C APIs, including support for
 standard I/O, file I/O, filesystem manipulation, memory management, time, string,
-environment variables, program startup, multithreading, networkign, and many other
-APIs.
+environment variables, program startup, and many other APIs.
+
+WASI Libc is sufficiently stable and usable for many purposes, as most of the
+POSIX-compatible APIs are stable, though it is continuing to evolve to better
+align with wasm and WASI. For example, pthread support is still a work in
+progress.
 
 ## Usage