Implement missing unistd readv()

system/lib/libc/musl/src/unistd/readv.c

@@ -4,5 +4,13 @@
 
 ssize_t readv(int fd, const struct iovec *iov, int count)
 {
+#if __EMSCRIPTEN__
+	size_t num;
+	if (__wasi_syscall_ret(__wasi_fd_read(fd, (struct __wasi_iovec_t*)iov, count, &num))) {
+		num = -1;
+	}
+	return num;
+#else
 	return syscall_cp(SYS_readv, fd, iov, count);
+#endif
 }

tests/unistd/io.c

@@ -10,6 +10,7 @@
 #include <unistd.h>
 #include <fcntl.h>
 #include <string.h>
+#include <sys/uio.h>
 #include <emscripten.h>
 
 int main() {
@@ -188,5 +189,25 @@ int main() {
   }
   printf("\n");
 
+  // readv
+  printf("\n");
+  memset(readBuffer, 0, sizeof readBuffer);
+  struct iovec iov;
+  iov.iov_base = readBuffer;
+  iov.iov_len = sizeof readBuffer;
+  printf("seek: %d\n", lseek(f, 0, SEEK_SET));
+  printf("read after write: %d\n", bytesRead = readv(f, &iov, 1));
+  printf("errno: %d\n", errno);
+  errno = 0;
+  printf("final: ");
+  for (int i = 0; i < bytesRead; i++) {
+    if (readBuffer[i] == 0) {
+      printf("\\0");
+    } else {
+      printf("%c", readBuffer[i]);
+    }
+  }
+  printf("\n");
+
   return 0;
 }

tests/unistd/io.out

@@ -78,3 +78,8 @@ seek: 0
 read after write: 37
 errno: 0
 final: wri4567890wri\0\0\0\0ite\0\0\0writeme\0\0write
+
+seek: 0
+read after write: 37
+errno: 0
+final: wri4567890wri\0\0\0\0ite\0\0\0writeme\0\0write