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* [gcc r12-9908] libstdc++: Make std::filesystem::copy_file work for procfs [PR108178]
@ 2023-10-03 16:11 Jonathan Wakely
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From: Jonathan Wakely @ 2023-10-03 16:11 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:f85947338197b12b77aa5eb0eb2d1b4ea7dbdd54
commit r12-9908-gf85947338197b12b77aa5eb0eb2d1b4ea7dbdd54
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Tue Mar 21 12:29:08 2023 +0000
libstdc++: Make std::filesystem::copy_file work for procfs [PR108178]
The size reported by stat is always zero for some special files such as
those under /proc, which means the current copy_file implementation
thinks there is nothing to copy. Instead of trusting the stat value, try
to read a character from a streambuf and check for EOF.
For the backport, we also need to avoid trying to use sendfile when stat
reports a zero size, so that we use streambufs to copy the file.
libstdc++-v3/ChangeLog:
PR libstdc++/108178
* src/filesystem/ops-common.h (do_copy_file): Check for empty
files by trying to read a character.
* testsuite/27_io/filesystem/operations/copy_file_108178.cc:
New test.
(cherry picked from commit 07a0e108247f23fcb919c61595adae143f1ea02a)
Diff:
---
libstdc++-v3/src/filesystem/ops-common.h | 46 +++++++++++++---------
.../filesystem/operations/copy_file_108178.cc | 33 ++++++++++++++++
2 files changed, 61 insertions(+), 18 deletions(-)
diff --git a/libstdc++-v3/src/filesystem/ops-common.h b/libstdc++-v3/src/filesystem/ops-common.h
index 3a78380c814..789e39522a8 100644
--- a/libstdc++-v3/src/filesystem/ops-common.h
+++ b/libstdc++-v3/src/filesystem/ops-common.h
@@ -501,25 +501,29 @@ _GLIBCXX_BEGIN_NAMESPACE_FILESYSTEM
size_t count = from_st->st_size;
#if defined _GLIBCXX_USE_SENDFILE && ! defined _GLIBCXX_FILESYSTEM_IS_WINDOWS
- off_t offset = 0;
- ssize_t n = ::sendfile(out.fd, in.fd, &offset, count);
- if (n < 0 && errno != ENOSYS && errno != EINVAL)
+ ssize_t n = 0;
+ if (count != 0)
{
- ec.assign(errno, std::generic_category());
- return false;
- }
- if ((size_t)n == count)
- {
- if (!out.close() || !in.close())
+ off_t offset = 0;
+ n = ::sendfile(out.fd, in.fd, &offset, count);
+ if (n < 0 && errno != ENOSYS && errno != EINVAL)
{
ec.assign(errno, std::generic_category());
return false;
}
- ec.clear();
- return true;
+ if ((size_t)n == count)
+ {
+ if (!out.close() || !in.close())
+ {
+ ec.assign(errno, std::generic_category());
+ return false;
+ }
+ ec.clear();
+ return true;
+ }
+ else if (n > 0)
+ count -= n;
}
- else if (n > 0)
- count -= n;
#endif // _GLIBCXX_USE_SENDFILE
using std::ios;
@@ -549,11 +553,17 @@ _GLIBCXX_BEGIN_NAMESPACE_FILESYSTEM
}
#endif
- if (count && !(std::ostream(&sbout) << &sbin))
- {
- ec = std::make_error_code(std::errc::io_error);
- return false;
- }
+ // ostream::operator<<(streambuf*) fails if it extracts no characters,
+ // so don't try to use it for empty files. But from_st->st_size == 0 for
+ // some special files (e.g. procfs, see PR libstdc++/108178) so just try
+ // to read a character to decide whether there is anything to copy or not.
+ if (sbin.sgetc() != char_traits<char>::eof())
+ if (!(std::ostream(&sbout) << &sbin))
+ {
+ ec = std::make_error_code(std::errc::io_error);
+ return false;
+ }
+
if (!sbout.close() || !sbin.close())
{
ec.assign(errno, std::generic_category());
diff --git a/libstdc++-v3/testsuite/27_io/filesystem/operations/copy_file_108178.cc b/libstdc++-v3/testsuite/27_io/filesystem/operations/copy_file_108178.cc
new file mode 100644
index 00000000000..25135834e21
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/filesystem/operations/copy_file_108178.cc
@@ -0,0 +1,33 @@
+// { dg-do run { target c++17 } }
+// { dg-require-filesystem-ts "" }
+
+// C++17 30.10.15.4 Copy [fs.op.copy_file]
+
+#include <filesystem>
+#include <fstream>
+#include <unistd.h> // getpid
+#include <testsuite_fs.h>
+#include <testsuite_hooks.h>
+
+namespace fs = std::filesystem;
+
+void
+test_procfs() // PR libstdc++/108178
+{
+ auto pid = ::getpid();
+ std::string from = "/proc/" + std::to_string(pid) + "/status";
+ if (fs::exists(from))
+ {
+ auto to = __gnu_test::nonexistent_path();
+ fs::copy_file(from, to);
+ std::ifstream f(to);
+ VERIFY(f.is_open());
+ VERIFY(f.peek() != std::char_traits<char>::eof());
+ fs::remove(to);
+ }
+}
+
+int main()
+{
+ test_procfs();
+}
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