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libstdc++: Fix error handling in fs::hard_link_count for Windows

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The recent change to use auto_win_file_handle for
std::filesystem::hard_link_count caused a regression. The
std::error_code argument should be cleared if no error occurs, but this
no longer happens. Add a call to ec.clear() in fs::hard_link_count to
fix this.

Also change the auto_win_file_handle class to take a reference to the
std::error_code and set it if an error occurs, to slightly simplify the
control flow in the fs::equiv_files function.

libstdc++-v3/ChangeLog:

	* src/c++17/fs_ops.cc (auto_win_file_handle): Add error_code&
	member and set it if CreateFileW or GetFileInformationByHandle
	fails.
	(fs::equiv_files) [_GLIBCXX_FILESYSTEM_IS_WINDOWS]: Simplify
	control flow.
	(fs::hard_link_count) [_GLIBCXX_FILESYSTEM_IS_WINDOWS]: Clear ec
	on success.
	* testsuite/27_io/filesystem/operations/hard_link_count.cc:
	Check error handling.
This commit is contained in:
Jonathan Wakely 2024-09-02 12:16:49 +01:00 • committed by Jonathan Wakely
parent 819deae0a5
commit 71b1639c67
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2 changed files with 57 additions and 26 deletions
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59
libstdc++-v3/src/c++17/fs_ops.cc
View file

@ -829,23 +829,37 @@ namespace
struct auto_win_file_handle
{
explicit
auto_win_file_handle(const wchar_t* p)
auto_win_file_handle(const wchar_t* p, std::error_code& ec) noexcept
: handle(CreateFileW(p, 0,
FILE_SHARE_DELETE | FILE_SHARE_READ | FILE_SHARE_WRITE,
0, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, 0))
{ }
0, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, 0)),
ec(ec)
{
if (handle == INVALID_HANDLE_VALUE)
ec = std::__last_system_error();
}
~auto_win_file_handle()
{ if (*this) CloseHandle(handle); }
explicit operator bool() const
explicit operator bool() const noexcept
{ return handle != INVALID_HANDLE_VALUE; }
bool get_info()
{ return GetFileInformationByHandle(handle, &info); }
bool get_info() noexcept
{
if (GetFileInformationByHandle(handle, &info))
return true;
ec = std::__last_system_error();
return false;
}
HANDLE handle;
BY_HANDLE_FILE_INFORMATION info;
// Like errno, we only set this on error and never clear it.
// This propagates an error_code to the caller when something goes wrong,
// but the caller should not assume a non-zero ec means an error happened
// unless they explicitly cleared it before passing it to our constructor.
std::error_code& ec;
};
}
#endif
@ -866,23 +880,14 @@ fs::equiv_files([[maybe_unused]] const char_type* p1, const stat_type& st1,
if (st1.st_mode != st2.st_mode || st1.st_dev != st2.st_dev)
return false;
// Need to use GetFileInformationByHandle to get more info about the files.
auto_win_file_handle h1(p1);
auto_win_file_handle h2(p2);
if (!h1 || !h2)
{
if (!h1 && !h2)
ec = __last_system_error();
return false;
}
if (!h1.get_info() || !h2.get_info())
{
ec = __last_system_error();
return false;
}
return h1.info.dwVolumeSerialNumber == h2.info.dwVolumeSerialNumber
&& h1.info.nFileIndexHigh == h2.info.nFileIndexHigh
&& h1.info.nFileIndexLow == h2.info.nFileIndexLow;
// Use GetFileInformationByHandle to get more info about the files.
if (auto_win_file_handle h1{p1, ec})
if (auto_win_file_handle h2{p2, ec})
if (h1.get_info() && h2.get_info())
return h1.info.dwVolumeSerialNumber == h2.info.dwVolumeSerialNumber
&& h1.info.nFileIndexHigh == h2.info.nFileIndexHigh
&& h1.info.nFileIndexLow == h2.info.nFileIndexLow;
return false;
#endif // _GLIBCXX_FILESYSTEM_IS_WINDOWS
}
#endif // NEED_DO_COPY_FILE
@ -1007,10 +1012,12 @@ std::uintmax_t
fs::hard_link_count(const path& p, error_code& ec) noexcept
{
#if _GLIBCXX_FILESYSTEM_IS_WINDOWS
auto_win_file_handle h(p.c_str());
auto_win_file_handle h(p.c_str(), ec);
if (h && h.get_info())
return static_cast<uintmax_t>(h.info.nNumberOfLinks);
ec = __last_system_error();
{
ec.clear();
return static_cast<uintmax_t>(h.info.nNumberOfLinks);
}
return static_cast<uintmax_t>(-1);
#elif defined _GLIBCXX_HAVE_SYS_STAT_H
return do_stat(p, ec, std::mem_fn(&stat_type::st_nlink),

24
libstdc++-v3/testsuite/27_io/filesystem/operations/hard_link_count.cc
View file

@ -30,8 +30,32 @@ void test01()
VERIFY( fs::hard_link_count(p2) == 2 );
}
void
test02()
{
std::error_code ec;
fs::path p1 = __gnu_test::nonexistent_path();
VERIFY( fs::hard_link_count(p1, ec) == -1 );
VERIFY( ec == std::errc::no_such_file_or_directory );
#if __cpp_exceptions
try {
fs::hard_link_count(p1); // { dg-warning "ignoring return value" }
VERIFY( false );
} catch (const fs::filesystem_error& e) {
VERIFY( e.path1() == p1 );
VERIFY( e.path2().empty() );
}
#endif
__gnu_test::scoped_file f1(p1);
fs::hard_link_count(f1.path, ec); // { dg-warning "ignoring return value" }
VERIFY( !ec ); // Should be cleared on success.
}
int
main()
{
test01();
test02();
}