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Fix Windows temp-file cleanup failing on paths over MAX_PATH #9452

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Fix Windows temp-file cleanup failing on paths over MAX_PATH #9452

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9eedfd2
Fix Windows temp-file cleanup failing on paths over MAX_PATH
alexreinking Sep 15, 2026
9e5ab03
Clean up comments
alexreinking Sep 15, 2026
baa9af0
Use to_long_path in more places.
alexreinking Sep 16, 2026
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41 changes: 34 additions & 7 deletions src/Util.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -104,6 +104,25 @@ std::wstring from_utf8(const std::string &str) {
return wstr;
}

// Prepend \\?\ to the path if it's an absolute drive path and doesn't
// already have it. This is needed for some Windows APIs that don't
// support long paths otherwise.
std::wstring to_long_path(const std::string &str) {
std::wstring wstr = from_utf8(str);
for (auto &c : wstr) {
if (c == L'/') {
c = L'\\';
}
}
bool is_absolute_drive_path = wstr.size() >= 2 &&
((wstr[0] >= L'A' && wstr[0] <= L'Z') || (wstr[0] >= L'a' && wstr[0] <= L'z')) &&
wstr[1] == L':';
if (is_absolute_drive_path && wstr.rfind(LR"(\\?\)", 0) != 0) {
wstr = LR"(\\?\)" + wstr;
}
return wstr;
}

} // namespace
#endif

Expand Down Expand Up @@ -316,7 +335,7 @@ std::string strip_namespaces(const std::string &name) {

bool file_exists(const std::string &name) {
#ifdef _MSC_VER
return _access(name.c_str(), 0) == 0;
return _waccess(to_long_path(name).c_str(), 0) == 0;
#else
return ::access(name.c_str(), F_OK) == 0;
#endif
Expand All @@ -332,7 +351,7 @@ void assert_no_file_exists(const std::string &name) {

void file_unlink(const std::string &name) {
#ifdef _MSC_VER
_unlink(name.c_str());
DeleteFileW(to_long_path(name).c_str());
#else
::unlink(name.c_str());
#endif
Expand All @@ -347,7 +366,7 @@ void ensure_no_file_exists(const std::string &name) {

void dir_rmdir(const std::string &name) {
#ifdef _MSC_VER
std::wstring wname = from_utf8(name);
std::wstring wname = to_long_path(name);
internal_assert(RemoveDirectoryW(wname.c_str()))
<< "RemoveDirectoryW() failed to remove " << name << "; error " << GetLastError() << "\n";
#else
Expand All @@ -359,7 +378,7 @@ void dir_rmdir(const std::string &name) {
FileStat file_stat(const std::string &name) {
#ifdef _MSC_VER
struct _stat a;
if (_stat(name.c_str(), &a) != 0) {
if (_wstat(to_long_path(name).c_str(), &a) != 0) {
user_error << "Could not stat " << name << "\n";
}
#else
Expand Down Expand Up @@ -463,7 +482,7 @@ std::string dir_make_temp() {
name << (int)guid.Data4[i];
}
std::string dir = tmp_dir + name.str();
std::wstring wdir = from_utf8(dir);
std::wstring wdir = to_long_path(dir);
BOOL success = CreateDirectoryW(wdir.c_str(), nullptr);
if (success) {
debug(1) << "temp dir is: " << dir << "\n";
Expand All @@ -489,7 +508,11 @@ std::string dir_make_temp() {
}

std::vector<char> read_entire_file(const std::string &pathname) {
#ifdef _MSC_VER
std::ifstream f(to_long_path(pathname).c_str(), std::ios::in | std::ios::binary);
#else
std::ifstream f(pathname, std::ios::in | std::ios::binary);
#endif
std::vector<char> result;

f.seekg(0, std::ifstream::end);
Expand All @@ -503,7 +526,11 @@ std::vector<char> read_entire_file(const std::string &pathname) {
}

void write_entire_file(const std::string &pathname, const void *source, size_t source_len) {
#ifdef _MSC_VER
std::ofstream f(to_long_path(pathname).c_str(), std::ios::out | std::ios::binary);
#else
std::ofstream f(pathname, std::ios::out | std::ios::binary);
#endif

f.write(reinterpret_cast<const char *>(source), source_len);
f.flush();
Expand Down Expand Up @@ -536,7 +563,7 @@ int run_process(std::vector<std::string> args, const std::string &stdout_path, c
int saved_stdout = -1, saved_stderr = -1;
if (!stdout_path.empty()) {
saved_stdout = _dup(_fileno(stdout));
int fd = _open(stdout_path.c_str(), _O_WRONLY | _O_CREAT | _O_TRUNC | _O_BINARY, _S_IWRITE);
int fd = _wopen(to_long_path(stdout_path).c_str(), _O_WRONLY | _O_CREAT | _O_TRUNC | _O_BINARY, _S_IWRITE);
if (fd == -1) {
if (saved_stdout != -1) {
_close(saved_stdout);
Expand All @@ -555,7 +582,7 @@ int run_process(std::vector<std::string> args, const std::string &stdout_path, c
// writes would clobber each other instead of concatenating.
_dup2(_fileno(stdout), _fileno(stderr));
} else {
int fd = _open(stderr_path.c_str(), _O_WRONLY | _O_CREAT | _O_TRUNC | _O_BINARY, _S_IWRITE);
int fd = _wopen(to_long_path(stderr_path).c_str(), _O_WRONLY | _O_CREAT | _O_TRUNC | _O_BINARY, _S_IWRITE);
if (fd == -1) {
if (saved_stdout != -1) {
_dup2(saved_stdout, _fileno(stdout));
Expand Down
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