[PATCH] libstdc++: retry removal of dir entries if dir removal fails

[Alexandre Oliva <oliva@adacore.com>]

On some target systems (e.g. rtems6.0), removing directory components
while iterating over directory entries may cause some of the directory
entries to be skipped, which prevents the removal of the parent
directory from succeeding.

Advancing the iterator before removing a member proved not to be
enough, so I've instead arranged for remove_all to retry the removal
of components if the removal of the parent dir fails after removing at
least one entry.  The fail will be permanent only if no components got
removed in the current try.

Regstrapped on x86_64-linux-gnu, also tested with a cross to
aarch64-rtems6.  Ok to install?

PS: The implementation of remove_all has changed completely, compared
with the gcc-11 environment in which the need for this patch came up.  I
have reimplemented it for mainline, and I have attempted to test it in
this environment, but new filesystem tests and subtests that fail on
rtems6.0 have impaired testing and prevented the full pass rate I got
for them with a similar patchset on gcc-11.


for  libstdc++-v3/ChangeLog

	* src/c++17/fs_ops.cc (remove_all): Retry removal of
	directory entries.
---
 libstdc++-v3/src/c++17/fs_ops.cc |   22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/src/c++17/fs_ops.cc b/libstdc++-v3/src/c++17/fs_ops.cc
index 435368fa5c5ff..b3390310132b4 100644
--- a/libstdc++-v3/src/c++17/fs_ops.cc
+++ b/libstdc++-v3/src/c++17/fs_ops.cc
@@ -1286,6 +1286,8 @@ fs::remove_all(const path& p)
 {
   error_code ec;
   uintmax_t count = 0;
+ retry:
+  uintmax_t init_count = count;
   recursive_directory_iterator dir(p, directory_options{64|128}, ec);
   switch (ec.value()) // N.B. assumes ec.category() == std::generic_category()
   {
@@ -1303,7 +1305,7 @@ fs::remove_all(const path& p)
     break;
   case ENOENT:
     // Our work here is done.
-    return 0;
+    return count;
   case ENOTDIR:
   case ELOOP:
     // Not a directory, will remove below.
@@ -1313,6 +1315,18 @@ fs::remove_all(const path& p)
     _GLIBCXX_THROW_OR_ABORT(filesystem_error("cannot remove all", p, ec));
   }
 
+  if (count > init_count)
+    {
+      if (int last = fs::remove(p, ec); !ec)
+	return count + last;
+      else
+	// Some systems seem to skip entries in the dir iteration if
+	// you remove dir entries while iterating, so if we removed
+	// anything in the dir in this round, and failed to remove
+	// the dir (presumably because it wasn't empty), retry.
+	goto retry;
+    }
+
   // Remove p itself, which is either a non-directory or is now empty.
   return count + fs::remove(p);
 }
@@ -1321,6 +1335,8 @@ std::uintmax_t
 fs::remove_all(const path& p, error_code& ec)
 {
   uintmax_t count = 0;
+ retry:
+  uintmax_t init_count = count;
   recursive_directory_iterator dir(p, directory_options{64|128}, ec);
   switch (ec.value()) // N.B. assumes ec.category() == std::generic_category()
   {
@@ -1341,7 +1357,7 @@ fs::remove_all(const path& p, error_code& ec)
   case ENOENT:
     // Our work here is done.
     ec.clear();
-    return 0;
+    return count;
   case ENOTDIR:
   case ELOOP:
     // Not a directory, will remove below.
@@ -1354,6 +1370,8 @@ fs::remove_all(const path& p, error_code& ec)
   // Remove p itself, which is either a non-directory or is now empty.
   if (int last = fs::remove(p, ec); !ec)
     return count + last;
+  if (count > init_count)
+    goto retry;
   return -1;
 }
 

-- 
Alexandre Oliva, happy hacker                https://FSFLA.org/blogs/lxo/
   Free Software Activist                       GNU Toolchain Engineer
Disinformation flourishes because many people care deeply about injustice
but very few check the facts.  Ask me about <https://stallmansupport.org>