[Xen-changelog] [xen stable-4.6] libxl: replace deprecated readdir_r() with readdir()

[patchbot@xxxxxxx]

commit 4afdf4de19c1e7375e09b2227e9373052abbeff7
Author:     Chris Patterson <pattersonc@xxxxxxxxxxxx>
AuthorDate: Fri Jun 3 12:50:09 2016 -0400
Commit:     Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
CommitDate: Wed May 29 12:03:45 2019 +0100

    libxl: replace deprecated readdir_r() with readdir()
    
    Replace the usage of readdir_r() with readdir() to address a
    compilation error under glibc due to the deprecation of readdir_r
    for their next release (2.24) [1, 2].
    
    Remove code specific to usage of readdir_r which is no longer required,
    such as zalloc_dirent().
    
    --
    
    From the GNU libc manual [3]:
    "
     It is expected that future versions of POSIX will obsolete readdir_r and
     mandate the level of thread safety for readdir which is provided by the
     GNU C Library and other implementations today.
    "
    
    There is a filed bug in the Austin Group Defect Tracker [4]  in which 
'dalias'
    proposes (in comment 0001632) that:
    "
       I would like to propose an alternate solution. For readdir, replace the 
text:
        "The readdir() function need not be thread-safe."
       with:
        "If multiple threads call the readdir() function with the same directory
        stream argument and without synchronization to preclude simultaneous
        access, then the behavior is undefined."
    
       With this change, the clunky readdir_r function is no longer needed or
       useful, and should probably be deprecated. As the only reasonable way
       to meet the implementation requirements for readdir is to have the dirent
       buffer in the DIR structure, this change should not require any change to
       existing implementations.
    "
    
    [1] https://sourceware.org/ml/libc-alpha/2016-02/msg00093.html
    [2] https://sourceware.org/bugzilla/show_bug.cgi?id=19056
    [3] 
https://www.gnu.org/software/libc/manual/html_node/Reading_002fClosing-Directory.html
    [4] http://austingroupbugs.net/view.php?id=696
    
    Signed-off-by: Chris Patterson <pattersonc@xxxxxxxxxxxx>
    Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
    Release-acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
    (cherry picked from commit b9daff9d811285f1e40669bc621c2241793f7a95)
---
 tools/libxl/libxl_utils.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/tools/libxl/libxl_utils.c b/tools/libxl/libxl_utils.c
index 408ec858a8..88371655c8 100644
--- a/tools/libxl/libxl_utils.c
+++ b/tools/libxl/libxl_utils.c
@@ -471,14 +471,12 @@ int libxl__remove_directory(libxl__gc *gc, const char 
*dirpath)
         goto out;
     }
 
-    size_t need = offsetof(struct dirent, d_name) +
-        pathconf(dirpath, _PC_NAME_MAX) + 1;
-    struct dirent *de_buf = libxl__zalloc(gc, need);
     struct dirent *de;
 
     for (;;) {
-        int r = readdir_r(d, de_buf, &de);
-        if (r) {
+        errno = 0;
+        de = readdir(d);
+        if (!de && errno) {
             LOGE(ERROR, "failed to readdir %s for removal", dirpath);
             rc = ERROR_FAIL;
             break;
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.6

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