ar: fix modification of existing archives

When modifying an existing archive the code opens the old file, unlinks
it and creates a new file with the same name.  This doesn't work on
Windows where it isn't possible to unlink an open file.  Instead we
create a temporary file for output and change it's name when we're done.

1 files changed, 15 insertions, 1 deletions

diff --git a/archival/ar.c b/archival/ar.c
index f86c52d9b..89e6a1207 100644
--- a/archival/ar.c
+++ b/archival/ar.c
@@ -175,6 +175,7 @@ static int write_ar_archive(archive_handle_t *handle)
 {
         struct stat st;
         archive_handle_t *out_handle;
+        char *temp_fn = NULL;
 
         xfstat(handle->src_fd, &st, handle->ar__name);
 
@@ -183,8 +184,14 @@ static int write_ar_archive(archive_handle_t *handle)
          */
         if (st.st_size != 0) {
                 out_handle = init_handle();
+#if !ENABLE_PLATFORM_MINGW32
                 xunlink(handle->ar__name);
                 out_handle->src_fd = xopen(handle->ar__name, O_WRONLY | O_CREAT | O_TRUNC);
+#else
+                /* can't unlink open file, create temporary output file */
+                temp_fn = xasprintf("%sXXXXXX", handle->ar__name);
+                out_handle->src_fd = xmkstemp(temp_fn);
+#endif
                 out_handle->accept = handle->accept;
         } else {
                 out_handle = handle;
@@ -206,12 +213,19 @@ static int write_ar_archive(archive_handle_t *handle)
                 continue;
 
         /* optional, since we exit right after we return */
-        if (ENABLE_FEATURE_CLEAN_UP) {
+        if (ENABLE_FEATURE_CLEAN_UP || ENABLE_PLATFORM_MINGW32) {
                 close(handle->src_fd);
                 if (out_handle->src_fd != handle->src_fd)
                         close(out_handle->src_fd);
         }
 
+#if ENABLE_PLATFORM_MINGW32
+        if ( temp_fn != NULL ) {
+                xrename(temp_fn, handle->ar__name);
+                free(temp_fn);
+        }
+#endif
+
         return EXIT_SUCCESS;
 }
 #endif /* FEATURE_AR_CREATE */