test: add WASI test for file resizing

This commit adds a WASI test to cover the following functions:

- __wasi_fd_filestat_set_size()
- __wasi_fd_tell()

PR-URL: #31617
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

test/wasi/c/ftruncate.c

@@ -0,0 +1,39 @@
+#include <sys/stat.h>
+#include <assert.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#define BASE_DIR "/tmp"
+#define OUTPUT_DIR BASE_DIR "/testdir"
+#define PATH OUTPUT_DIR "/output.txt"
+
+int main(void) {
+  struct stat st;
+  int fd;
+
+  (void)st;
+  assert(0 == mkdir(OUTPUT_DIR, 0755));
+
+  fd = open(PATH, O_CREAT | O_WRONLY, 0666);
+  assert(fd != -1);
+
+  /* Verify that the file is initially empty. */
+  assert(0 == fstat(fd, &st));
+  assert(st.st_size == 0);
+  assert(0 == lseek(fd, 0, SEEK_CUR));
+
+  /* Increase the file size using ftruncate(). */
+  assert(0 == ftruncate(fd, 500));
+  assert(0 == fstat(fd, &st));
+  assert(st.st_size == 500);
+  assert(0 == lseek(fd, 0, SEEK_CUR));
+
+  /* Truncate the file using ftruncate(). */
+  assert(0 == ftruncate(fd, 300));
+  assert(0 == fstat(fd, &st));
+  assert(st.st_size == 300);
+  assert(0 == lseek(fd, 0, SEEK_CUR));
+
+  assert(0 == close(fd));
+  return 0;
+}

test/wasi/test-wasi.js

@@ -71,6 +71,7 @@ if (process.argv[2] === 'wasi-child') {
   runWASI({ test: 'exitcode', exitCode: 120 });
   runWASI({ test: 'fd_prestat_get_refresh' });
   runWASI({ test: 'freopen', stdout: `hello from input2.txt${EOL}` });
+  runWASI({ test: 'ftruncate' });
   runWASI({ test: 'getentropy' });
 
   // Tests that are currently unsupported on IBM i PASE.