@@ -962,26 +962,45 @@ fs::read_symlink(const path& p)
fs::path fs::read_symlink(const path& p, error_code& ec)
{
+ path result;
#ifdef _GLIBCXX_HAVE_SYS_STAT_H
stat_type st;
if (::lstat(p.c_str(), &st))
{
ec.assign(errno, std::generic_category());
- return {};
+ return result;
}
- std::string buf(st.st_size, '\0');
- ssize_t len = ::readlink(p.c_str(), &buf.front(), buf.size());
- if (len == -1)
+ std::string buf(st.st_size ? st.st_size + 1 : 128, '\0');
+ do
{
- ec.assign(errno, std::generic_category());
- return {};
+ ssize_t len = ::readlink(p.c_str(), buf.data(), buf.size());
+ if (len == -1)
+ {
+ ec.assign(errno, std::generic_category());
+ return result;
+ }
+ else if (len == (ssize_t)buf.size())
+ {
+ if (buf.size() > 4096)
+ {
+ ec.assign(ENAMETOOLONG, std::generic_category());
+ return result;
+ }
+ buf.resize(buf.size() * 2);
+ }
+ else
+ {
+ buf.resize(len);
+ result.assign(buf);
+ ec.clear();
+ break;
+ }
}
- ec.clear();
- return path{buf.data(), buf.data()+len};
+ while (true);
#else
ec = std::make_error_code(std::errc::not_supported);
- return {};
#endif
+ return result;
}
@@ -24,6 +24,7 @@
#ifndef _GLIBCXX_USE_CXX11_ABI
# define _GLIBCXX_USE_CXX11_ABI 1
+# define NEED_DO_COPY_FILE
#endif
#include <filesystem>
@@ -251,6 +252,7 @@ namespace std::filesystem
}
#ifdef _GLIBCXX_HAVE_SYS_STAT_H
+#ifdef NEED_DO_COPY_FILE
bool
fs::do_copy_file(const char* from, const char* to,
copy_options_existing_file options,
@@ -423,6 +425,7 @@ fs::do_copy_file(const char* from, const char* to,
return true;
#endif // _GLIBCXX_USE_SENDFILE
}
+#endif // NEED_DO_COPY_FILE
#endif // _GLIBCXX_HAVE_SYS_STAT_H
void
@@ -1166,26 +1169,45 @@ fs::read_symlink(const path& p)
fs::path fs::read_symlink(const path& p, error_code& ec)
{
+ path result;
#ifdef _GLIBCXX_HAVE_SYS_STAT_H
stat_type st;
if (::lstat(p.c_str(), &st))
{
ec.assign(errno, std::generic_category());
- return {};
+ return result;
}
- std::string buf(st.st_size, '\0');
- ssize_t len = ::readlink(p.c_str(), &buf.front(), buf.size());
- if (len == -1)
+ std::string buf(st.st_size ? st.st_size + 1 : 128, '\0');
+ do
{
- ec.assign(errno, std::generic_category());
- return {};
+ ssize_t len = ::readlink(p.c_str(), buf.data(), buf.size());
+ if (len == -1)
+ {
+ ec.assign(errno, std::generic_category());
+ return result;
+ }
+ else if (len == (ssize_t)buf.size())
+ {
+ if (buf.size() > 4096)
+ {
+ ec.assign(ENAMETOOLONG, std::generic_category());
+ return result;
+ }
+ buf.resize(buf.size() * 2);
+ }
+ else
+ {
+ buf.resize(len);
+ result.assign(buf);
+ ec.clear();
+ break;
+ }
}
- ec.clear();
- return path{buf.data(), buf.data()+len};
+ while (true);
#else
ec = std::make_error_code(std::errc::not_supported);
- return {};
#endif
+ return result;
}
fs::path
For some paths lstat returns st_size == 0, so use a buffer with non-zero size and then grow it dynamically if it's not big enough. PR libstdc++/79283 * src/filesystem/ops.cc (read_symlink): Handle st_size being zero. * src/filesystem/std-ops.cc (read_symlink): Likewise. (do_copy_file) [!NEED_DO_COPY_FILE]: Avoid multiple definitions. Tested x86+64-linux, committed to trunk. I'll backport the experimental::filesystem::read_symlink part to the branches. commit ef737409818853af3a2b9a8b22984194d8c61de7 Author: Jonathan Wakely <jwakely@redhat.com> Date: Wed Oct 25 02:15:25 2017 +0100 PR libstdc++/79283 fix filesystem::read_symlink for /proc PR libstdc++/79283 * src/filesystem/ops.cc (read_symlink): Handle st_size being zero. * src/filesystem/std-ops.cc (read_symlink): Likewise. (do_copy_file) [!NEED_DO_COPY_FILE]: Avoid multiple definitions.