Implement SA_RESTART for read and write.

tests/Makefile

@@ -31,6 +31,7 @@ EXPECT_NAMES=\
 	setjmp \
 	sigaction \
 	signal \
+	sa_restart \
 	stdio/all \
 	stdio/buffer \
 	stdio/fgets \

tests/sa_restart.c

@@ -0,0 +1,53 @@
+#include <assert.h>
+#include <signal.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include "test_helpers.h"
+
+void action(int sig, siginfo_t *info, void *context) {
+    assert (sig == SIGUSR1);
+    (void)info;
+    (void)context;
+    char *msg = "Signal handler\n";
+    write(1, msg, strlen(msg));
+    _exit(0);
+}
+
+int main(void) {
+    int status;
+
+    struct sigaction act;
+    act.sa_sigaction = action;
+    act.sa_flags = SA_RESTART;
+    sigemptyset(&act.sa_mask);
+
+    status = sigaction(SIGUSR1, &act, NULL);
+    ERROR_IF(sigaction, status, == -1);
+
+    int fds[2];
+    status = pipe(fds);
+    ERROR_IF(pipe, status, == -1);
+
+    int parent = getpid();
+
+    status = fork();
+    ERROR_IF(fork, status, == -1);
+
+    if (status == 0) {
+        for (int i = 0; i < 1000; i++) {
+            status = kill(parent, SIGUSR1);
+            ERROR_IF(kill, status, == -1);
+        }
+        return 0;
+    }
+
+    char buffer[1];
+    status = read(fds[0], buffer, 1);
+    ERROR_IF(read, status, == -1);
+
+    return 1;
+}