Fix FILE_skip regression

The fseek* family of functions return 0 on success, not the new offset.
This is only true for lseek.

Fixes https://github.com/libarchive/libarchive/issues/2641
Fixes dcbf1e0ededa95849f098d154a25876ed5754bcf

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>

diff --git a/libarchive/archive_read_open_file.c b/libarchive/archive_read_open_file.c
index 6ed18a0c08eb45b109ad25facebaa8ebfb240e74..742923abbee99c6560fde6ad4a5727f2f5dd33bb 100644 (file)
--- a/libarchive/archive_read_open_file.c
+++ b/libarchive/archive_read_open_file.c
@@ -132,7 +132,7 @@ FILE_skip(struct archive *a, void *client_data, int64_t request)
 #else
        long skip = (long)request;
 #endif
-       int64_t old_offset, new_offset;
+       int64_t old_offset, new_offset = -1;
        int skip_bits = sizeof(skip) * 8 - 1;
 
        (void)a; /* UNUSED */
@@ -170,11 +170,14 @@ FILE_skip(struct archive *a, void *client_data, int64_t request)
 #ifdef __ANDROID__
                        new_offset = lseek(fileno(mine->f), skip, SEEK_CUR);
 #elif HAVE__FSEEKI64
-                       new_offset = _fseeki64(mine->f, skip, SEEK_CUR);
+                       if (_fseeki64(mine->f, skip, SEEK_CUR) == 0)
+                               new_offset = _ftelli64(mine->f);
 #elif HAVE_FSEEKO
-                       new_offset = fseeko(mine->f, skip, SEEK_CUR);
+                       if (fseeko(mine->f, skip, SEEK_CUR) == 0)
+                               new_offset = ftello(mine->f);
 #else
-                       new_offset = fseek(mine->f, skip, SEEK_CUR);
+                       if (fseek(mine->f, skip, SEEK_CUR) == 0)
+                               new_offset = ftell(mine->f);
 #endif
                        if (new_offset >= 0)
                                return (new_offset - old_offset);