Make improvements

- Invent openatemp() API
- Invent O_UNLINK open flag
- Introduce getenv_secure() API
- Remove `git pull` from cosmocc
- Fix utimes() when path is NULL
- Fix mktemp() to never return NULL
- Fix utimensat() UTIME_OMIT on XNU
- Improve utimensat() code for RHEL5
- Turn `argv[0]` C:/ to /C/ on Windows
- Introduce tmpnam() and tmpnam_r() APIs
- Fix more const issues with internal APIs
- Permit utimes() on WIN32 in O_RDONLY mode
- Fix fdopendir() to check fd is a directory
- Fix recent crash regression in landlock make
- Fix futimens(AT_FDCWD, NULL) to return EBADF
- Use workaround so `make -j` doesn't fork bomb
- Rename dontdiscard to __wur (just like glibc)
- Fix st_size for WIN32 symlinks containing UTF-8
- Introduce stdio ext APIs needed by GNU coreutils
- Fix lstat() on WIN32 for symlinks to directories
- Move some constants from normalize.inc to limits.h
- Fix segv with memchr() and memcmp() overlapping page
- Implement POSIX fflush() behavior for reader streams
- Implement AT_SYMLINK_NOFOLLOW for utimensat() on WIN32
- Don't change read-only status of existing files on WIN32
- Correctly handle `0x[^[:xdigit:]]` case in strtol() functions

test/libc/stdio/ungetc_test.c

@@ -16,6 +16,9 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/calls.h"
+#include "libc/nexgen32e/crc32.h"
+#include "libc/stdio/rand.h"
 #include "libc/stdio/stdio.h"
 #include "libc/str/str.h"
 #include "libc/testlib/hyperion.h"
@@ -68,3 +71,28 @@ TEST(ungetwc, testGetWideChar_canBeUndoneWithinReason) {
   EXPECT_STREQ("𐌰𐌱\n", buf);
   EXPECT_EQ(0, fclose(f));
 }
+
+TEST(ungetc, io) {
+  static char b1[BUFSIZ * 2];
+  static char b2[BUFSIZ * 2];
+  for (int i = 0; i < sizeof(b1); ++i) {
+    b1[i] = rand();
+  }
+  FILE *f = tmpfile();
+  fwrite(b1, 1, sizeof(b1), f);
+  rewind(f);
+  for (int i = 0; i < sizeof(b1); ++i) {
+    int c;
+    ASSERT_NE(EOF, (c = fgetc(f)));
+    ASSERT_EQ(c, ungetc(c, f));
+    ASSERT_EQ(c, fgetc(f));
+    b2[i] = c;
+    if (rand() % 10 == 0) {
+      ASSERT_NE(EOF, fflush(f));
+      ASSERT_NE(i, lseek(fileno(f), 0, SEEK_CUR));
+    }
+  }
+  ASSERT_EQ(EOF, fgetc(f));
+  fclose(f);
+  ASSERT_EQ(crc32c(0, b1, sizeof(b1)), crc32c(0, b2, sizeof(b2)));
+}