From: Jonathan Wakely <jwakely@redhat.com>
To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org
Subject: [PATCH] PR libstdc++/79283 fix filesystem::read_symlink for /proc
Date: Wed, 25 Oct 2017 13:08:00 -0000 [thread overview]
Message-ID: <20171025124707.GA26781@redhat.com> (raw)
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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.
[-- Attachment #2: patch.txt --]
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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.
diff --git a/libstdc++-v3/src/filesystem/ops.cc b/libstdc++-v3/src/filesystem/ops.cc
index 61d9c89e616..1ec8883fde9 100644
--- a/libstdc++-v3/src/filesystem/ops.cc
+++ b/libstdc++-v3/src/filesystem/ops.cc
@@ -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;
}
diff --git a/libstdc++-v3/src/filesystem/std-ops.cc b/libstdc++-v3/src/filesystem/std-ops.cc
index ff7acbfc1e7..947be7ef4c5 100644
--- a/libstdc++-v3/src/filesystem/std-ops.cc
+++ b/libstdc++-v3/src/filesystem/std-ops.cc
@@ -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
reply other threads:[~2017-10-25 12:47 UTC|newest]
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