tar: fix exitcode check for MMU-spawned unpacking helpers

Testcase: tar xvzf EMPTY_FILE

function                                             old     new   delta
open_transformer                                     102     106      +4
get_header_tar                                      1781    1785      +4

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 10 insertions, 9 deletions

diff --git a/archival/libarchive/get_header_tar.c b/archival/libarchive/get_header_tar.c
index bc09756ba..32f842095 100644
--- a/archival/libarchive/get_header_tar.c
+++ b/archival/libarchive/get_header_tar.c
@@ -198,13 +198,13 @@ char FAST_FUNC get_header_tar(archive_handle_t *archive_handle)
          * the message and we don't check whether we indeed
          * saw zero block directly before this. */
         if (i == 0) {
-                xfunc_error_retval = 0;
- short_read:
-                bb_error_msg_and_die("short read");
+                bb_error_msg("short read");
+                /* this merely signals end of archive, not exit(1): */
+                return EXIT_FAILURE;
         }
         if (i != 512) {
                 IF_FEATURE_TAR_AUTODETECT(goto autodetect;)
-                goto short_read;
+                bb_error_msg_and_die("short read");
         }
 
 #else
@@ -221,10 +221,10 @@ char FAST_FUNC get_header_tar(archive_handle_t *archive_handle)
                          */
                         while (full_read(archive_handle->src_fd, &tar, 512) == 512)
                                 continue;
-                        return EXIT_FAILURE;
+                        return EXIT_FAILURE; /* "end of archive" */
                 }
                 archive_handle->tar__end = 1;
-                return EXIT_SUCCESS;
+                return EXIT_SUCCESS; /* "decoded one header" */
         }
         archive_handle->tar__end = 0;
 
@@ -471,5 +471,5 @@ char FAST_FUNC get_header_tar(archive_handle_t *archive_handle)
         free(file_header->tar__uname);
         free(file_header->tar__gname);
 #endif
-        return EXIT_SUCCESS;
+        return EXIT_SUCCESS; /* "decoded one header" */
 }
diff --git a/archival/libarchive/open_transformer.c b/archival/libarchive/open_transformer.c
index 4e44a87e9..4e9826441 100644
--- a/archival/libarchive/open_transformer.c
+++ b/archival/libarchive/open_transformer.c
@@ -79,16 +79,17 @@ void FAST_FUNC open_transformer(int fd, const char *transform_prog)
                 // FIXME: error check?
 #if BB_MMU
                 {
+                        IF_DESKTOP(long long) int r;
                         transformer_aux_data_t aux;
                         init_transformer_aux_data(&aux);
                         aux.check_signature = check_signature;
-                        transformer(&aux, fd, fd_pipe.wr);
+                        r = transformer(&aux, fd, fd_pipe.wr);
                         if (ENABLE_FEATURE_CLEAN_UP) {
                                 close(fd_pipe.wr); /* send EOF */
                                 close(fd);
                         }
                         /* must be _exit! bug was actually seen here */
-                        _exit(EXIT_SUCCESS);
+                        _exit(/*error if:*/ r < 0);
                 }
 #else
                 {