2 files changed, 91 insertions, 0 deletions
diff --git a/tests/runner.py b/tests/runner.py
index d16472ad..9d4df744 100755
--- a/tests/runner.py
+++ b/tests/runner.py
@@ -7142,6 +7142,10 @@ def process(filename):
         '''
       self.do_run(src, 'written=0')
 
+    def test_fgetc_ungetc(self):
+      src = open(path_from_root('tests', 'stdio', 'test_fgetc_ungetc.c'), 'r').read()
+      self.do_run(src, 'success', force_c=True)
+
     def test_fgetc_unsigned(self):
       if self.emcc_args is None: return self.skip('requires emcc')
       src = r'''
diff --git a/tests/stdio/test_fgetc_ungetc.c b/tests/stdio/test_fgetc_ungetc.c
new file mode 100644
index 00000000..c69a3d1a
--- /dev/null
+++ b/tests/stdio/test_fgetc_ungetc.c
@@ -0,0 +1,87 @@
+#include <assert.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+static void create_file(const char *path, const char *buffer, int mode) {
+  int fd = open(path, O_WRONLY | O_CREAT | O_EXCL, mode);
+  assert(fd >= 0);
+
+  int err = write(fd, buffer, sizeof(char) * strlen(buffer));
+  assert(err ==  (sizeof(char) * strlen(buffer)));
+
+  close(fd);
+}
+
+void setup() {
+  create_file("file.txt", "cd", 0666);
+}
+
+void cleanup() {
+  unlink("file.txt");
+}
+
+void test() {
+  FILE *file;
+  int err;
+  char buffer[256];
+
+  file = fopen("file.txt", "r");
+  assert(file);
+
+  // pushing EOF always returns EOF
+  rewind(file);
+  err = ungetc(EOF, file);
+  assert(err == EOF);
+
+  // ungetc should return itself
+  err = ungetc('a', file);
+  assert(err == (int)'a');
+
+  // push two chars and make sure they're read back in
+  // the correct order (both by fgetc and fread)
+  rewind(file);
+  ungetc('b', file);
+  ungetc('a', file);
+  err = fgetc(file);
+  assert(err == (int)'a');
+  fread(buffer, sizeof(char), sizeof(buffer), file);
+  assert(!strcmp(buffer, "bcd"));
+
+  // rewind and fseek should reset anything that's been
+  // pushed to the stream
+  ungetc('a', file);
+  rewind(file);
+  err = fgetc(file);
+  assert(err == (int)'c');
+  ungetc('a', file);
+  fseek(file, 0, SEEK_SET);
+  err = fgetc(file);
+  assert(err == (int)'c');
+
+  // fgetc, when nothing is left, should return EOF
+  fseek(file, 0, SEEK_END);
+  err = fgetc(file);
+  assert(err == EOF);
+  err = feof(file);
+  assert(err);
+
+  // ungetc should reset the EOF indicator
+  ungetc('e', file);
+  err = feof(file);
+  assert(!err);
+
+  fclose(file);
+
+  puts("success");
+}
+
+int main() {
+  atexit(cleanup);
+  signal(SIGABRT, cleanup);
+  setup();
+  test();
+  return EXIT_SUCCESS;
+}
+\ No newline at end of file