[committed] libstdc++: Use std::string::__resize_and_overwrite in std::filesystem
Jonathan Wakely
jwakely@redhat.com
Fri Sep 1 15:02:45 GMT 2023
Tested x86_64-linux. Pushed to trunk.
-- >8 --
There are a few places in the std::filesystem code that use a string as
a buffer for OS APIs to write to. We can use the new extension
__resize_and_overwrite to avoid redundant initialization of those
buffers.
libstdc++-v3/ChangeLog:
* src/c++17/fs_ops.cc (fs::absolute) [FILESYSTEM_IS_WINDOWS]:
Use __resize_and_overwrite to fill buffer.
(fs::read_symlink) [HAVE_READLINK]: Likewise.
* src/filesystem/ops-common.h (get_temp_directory_from_env)
[FILESYSTEM_IS_WINDOWS]: Likewise.
---
libstdc++-v3/src/c++17/fs_ops.cc | 45 ++++++++++++------------
libstdc++-v3/src/filesystem/ops-common.h | 7 ++--
2 files changed, 27 insertions(+), 25 deletions(-)
diff --git a/libstdc++-v3/src/c++17/fs_ops.cc b/libstdc++-v3/src/c++17/fs_ops.cc
index c94d260632f..6cdeac17c33 100644
--- a/libstdc++-v3/src/c++17/fs_ops.cc
+++ b/libstdc++-v3/src/c++17/fs_ops.cc
@@ -112,18 +112,17 @@ fs::absolute(const path& p, error_code& ec)
wstring buf;
do
{
- buf.resize(len);
- len = GetFullPathNameW(s.data(), len, buf.data(), nullptr);
+ buf.__resize_and_overwrite(len, [&s, &len](wchar_t* p, unsigned n) {
+ len = GetFullPathNameW(s.data(), n, p, nullptr);
+ return len > n ? 0 : len;
+ });
}
while (len > buf.size());
if (len == 0)
ec = __last_system_error();
else
- {
- buf.resize(len);
- ret = std::move(buf);
- }
+ ret = std::move(buf);
#else
ret = current_path(ec);
ret /= p;
@@ -1187,31 +1186,33 @@ fs::path fs::read_symlink(const path& p, error_code& ec)
return result;
}
- std::string buf(st.st_size ? st.st_size + 1 : 128, '\0');
+ std::string buf;
+ size_t bufsz = st.st_size ? st.st_size + 1 : 128;
do
{
- ssize_t len = ::readlink(p.c_str(), buf.data(), buf.size());
- if (len == -1)
+ ssize_t len;
+ buf.__resize_and_overwrite(bufsz, [&p, &len](char* ptr, size_t n) {
+ len = ::readlink(p.c_str(), ptr, n);
+ return size_t(len) < n ? len : 0;
+ });
+ if (buf.size())
+ {
+ result.assign(std::move(buf));
+ ec.clear();
+ break;
+ }
+ else if (len == -1)
{
ec.assign(errno, std::generic_category());
return result;
}
- else if (len == (ssize_t)buf.size())
+ else if (bufsz > 4096)
{
- if (buf.size() > 4096)
- {
- ec.assign(ENAMETOOLONG, std::generic_category());
- return result;
- }
- buf.resize(buf.size() * 2);
+ ec.assign(ENAMETOOLONG, std::generic_category());
+ return result;
}
else
- {
- buf.resize(len);
- result.assign(buf);
- ec.clear();
- break;
- }
+ bufsz *= 2;
}
while (true);
#else
diff --git a/libstdc++-v3/src/filesystem/ops-common.h b/libstdc++-v3/src/filesystem/ops-common.h
index 2e4331bb682..79dcb756453 100644
--- a/libstdc++-v3/src/filesystem/ops-common.h
+++ b/libstdc++-v3/src/filesystem/ops-common.h
@@ -700,8 +700,10 @@ _GLIBCXX_BEGIN_NAMESPACE_FILESYSTEM
std::wstring buf;
do
{
- buf.resize(len);
- len = GetTempPathW(buf.size(), buf.data());
+ buf.__resize_and_overwrite(len, [&len](wchar_t* p, unsigned n) {
+ len = GetTempPathW(n, p);
+ return len > n ? 0 : len;
+ });
}
while (len > buf.size());
@@ -710,7 +712,6 @@ _GLIBCXX_BEGIN_NAMESPACE_FILESYSTEM
else
ec.clear();
- buf.resize(len);
return buf;
}
#else
--
2.41.0
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