Improve some pthreads stub functions, batch 0 (#519)

This is one part of breaking up #518 into smaller PRs. This should be
(IMO) the least-controversial batch of commits

Author: ArcaneNibble

Makefile

@@ -288,12 +288,16 @@ LIBC_TOP_HALF_MUSL_SOURCES += \
         thread/pthread_attr_destroy.c \
         thread/pthread_attr_get.c \
         thread/pthread_attr_init.c \
-        thread/pthread_attr_setstack.c \
         thread/pthread_attr_setdetachstate.c \
+        thread/pthread_attr_setguardsize.c \
+        thread/pthread_attr_setstack.c \
         thread/pthread_attr_setstacksize.c \
         thread/pthread_barrier_destroy.c \
         thread/pthread_barrier_init.c \
         thread/pthread_barrier_wait.c \
+        thread/pthread_barrierattr_destroy.c \
+        thread/pthread_barrierattr_init.c \
+        thread/pthread_barrierattr_setpshared.c \
         thread/pthread_cleanup_push.c \
         thread/pthread_cond_broadcast.c \
         thread/pthread_cond_destroy.c \

expected/wasm32-wasip1-threads/defined-symbols.txt

@@ -992,12 +992,16 @@ pthread_attr_getstack
 pthread_attr_getstacksize
 pthread_attr_init
 pthread_attr_setdetachstate
+pthread_attr_setguardsize
 pthread_attr_setstack
 pthread_attr_setstacksize
 pthread_barrier_destroy
 pthread_barrier_init
 pthread_barrier_wait
+pthread_barrierattr_destroy
 pthread_barrierattr_getpshared
+pthread_barrierattr_init
+pthread_barrierattr_setpshared
 pthread_cond_broadcast
 pthread_cond_destroy
 pthread_cond_init

libc-top-half/musl/src/thread/pthread_attr_setguardsize.c

@@ -2,7 +2,12 @@
 
 int pthread_attr_setguardsize(pthread_attr_t *a, size_t size)
 {
+#ifdef __wasilibc_unmodified_upstream
 	if (size > SIZE_MAX/8) return EINVAL;
+#else
+	/* WASI doesn't have memory protection required for stack guards. */
+	if (size > 0) return EINVAL;
+#endif
 	a->_a_guardsize = size;
 	return 0;
 }

libc-top-half/musl/src/thread/pthread_mutexattr_setrobust.c

@@ -22,6 +22,7 @@ int pthread_mutexattr_setrobust(pthread_mutexattr_t *a, int robust)
 	a->__attr &= ~4;
 	return 0;
 #else
-	return EINVAL;
+	if (robust) return EINVAL;
+	return 0;
 #endif
 }