subprocess: Avoid leaking POSIX name aliases beyond subprocess.h

The commit a32c0f3df4b6bcd1d2e93f19e8f380bb890cd507 introduced code to
silence MSVC's "warning C4996: The POSIX name for this item is
deprecated."

However, it exhibits several issues:
1. The aliases may leak into code outside the `subprocess.hpp` header.
2. They are unnecessarily applied when using the MinGW-w64 toolchain.
3. The fix is incomplete: downstream projects still see C4996 warnings.
4. The implementation lacks documentation.

This change addresses all of the above shortcomings.

Github-Pull: arun11299/cpp-subprocess#112
Rebased-From: 778543b2f2ca7f5d1c4f0241b635bbb265d750dd

Co-authored-by: Luke Dashjr <luke-jr+git@utopios.org>
This commit is contained in:
Hennadii Stepanov 2025-04-27 17:23:20 +01:00
parent 7ecb4e430a
commit df7a52241f
No known key found for this signature in database
GPG key ID: 410108112E7EA81F

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@ -68,10 +68,6 @@ extern "C" {
#include <windows.h>
#include <io.h>
#include <cwchar>
#define close _close
#define open _open
#define fileno _fileno
#else
#include <sys/wait.h>
#include <unistd.h>
@ -81,6 +77,22 @@ extern "C" {
#include <sys/types.h>
}
// The Microsoft C++ compiler issues deprecation warnings
// for the standard POSIX function names.
// Its preferred implementations have a leading underscore.
// See: https://learn.microsoft.com/en-us/cpp/c-runtime-library/compatibility.
#if (defined _MSC_VER)
#define subprocess_close _close
#define subprocess_fileno _fileno
#define subprocess_open _open
#define subprocess_write _write
#else
#define subprocess_close close
#define subprocess_fileno fileno
#define subprocess_open open
#define subprocess_write write
#endif
/*!
* Getting started with reading this source code.
* The source is mainly divided into four parts:
@ -264,7 +276,7 @@ namespace util
FILE *fp = _fdopen(os_fhandle, mode);
if (fp == 0) {
_close(os_fhandle);
subprocess_close(os_fhandle);
throw OSError("_fdopen", 0);
}
@ -383,7 +395,7 @@ namespace util
{
size_t nwritten = 0;
while (nwritten < length) {
int written = write(fd, buf + nwritten, length - nwritten);
int written = subprocess_write(fd, buf + nwritten, length - nwritten);
if (written == -1) return -1;
nwritten += written;
}
@ -411,7 +423,7 @@ namespace util
#ifdef __USING_WINDOWS__
return (int)fread(buf, 1, read_upto, fp);
#else
int fd = fileno(fp);
int fd = subprocess_fileno(fp);
int rbytes = 0;
int eintr_cnter = 0;
@ -573,10 +585,10 @@ struct input
explicit input(int fd): rd_ch_(fd) {}
// FILE pointer.
explicit input (FILE* fp):input(fileno(fp)) { assert(fp); }
explicit input (FILE* fp):input(subprocess_fileno(fp)) { assert(fp); }
explicit input(const char* filename) {
int fd = open(filename, O_RDONLY);
int fd = subprocess_open(filename, O_RDONLY);
if (fd == -1) throw OSError("File not found: ", errno);
rd_ch_ = fd;
}
@ -606,10 +618,10 @@ struct output
{
explicit output(int fd): wr_ch_(fd) {}
explicit output (FILE* fp):output(fileno(fp)) { assert(fp); }
explicit output (FILE* fp):output(subprocess_fileno(fp)) { assert(fp); }
explicit output(const char* filename) {
int fd = open(filename, O_APPEND | O_CREAT | O_RDWR, 0640);
int fd = subprocess_open(filename, O_APPEND | O_CREAT | O_RDWR, 0640);
if (fd == -1) throw OSError("File not found: ", errno);
wr_ch_ = fd;
}
@ -637,10 +649,10 @@ struct error
{
explicit error(int fd): wr_ch_(fd) {}
explicit error(FILE* fp):error(fileno(fp)) { assert(fp); }
explicit error(FILE* fp):error(subprocess_fileno(fp)) { assert(fp); }
explicit error(const char* filename) {
int fd = open(filename, O_APPEND | O_CREAT | O_RDWR, 0640);
int fd = subprocess_open(filename, O_APPEND | O_CREAT | O_RDWR, 0640);
if (fd == -1) throw OSError("File not found: ", errno);
wr_ch_ = fd;
}
@ -803,28 +815,28 @@ public:
void cleanup_fds()
{
if (write_to_child_ != -1 && read_from_parent_ != -1) {
close(write_to_child_);
subprocess_close(write_to_child_);
}
if (write_to_parent_ != -1 && read_from_child_ != -1) {
close(read_from_child_);
subprocess_close(read_from_child_);
}
if (err_write_ != -1 && err_read_ != -1) {
close(err_read_);
subprocess_close(err_read_);
}
}
void close_parent_fds()
{
if (write_to_child_ != -1) close(write_to_child_);
if (read_from_child_ != -1) close(read_from_child_);
if (err_read_ != -1) close(err_read_);
if (write_to_child_ != -1) subprocess_close(write_to_child_);
if (read_from_child_ != -1) subprocess_close(read_from_child_);
if (err_read_ != -1) subprocess_close(err_read_);
}
void close_child_fds()
{
if (write_to_parent_ != -1) close(write_to_parent_);
if (read_from_parent_ != -1) close(read_from_parent_);
if (err_write_ != -1) close(err_write_);
if (write_to_parent_ != -1) subprocess_close(write_to_parent_);
if (read_from_parent_ != -1) subprocess_close(read_from_parent_);
if (err_write_ != -1) subprocess_close(err_write_);
}
FILE* input() { return input_.get(); }
@ -1161,8 +1173,8 @@ inline void Popen::execute_process() noexcept(false)
child_pid_ = fork();
if (child_pid_ < 0) {
close(err_rd_pipe);
close(err_wr_pipe);
subprocess_close(err_rd_pipe);
subprocess_close(err_wr_pipe);
throw OSError("fork failed", errno);
}
@ -1172,14 +1184,14 @@ inline void Popen::execute_process() noexcept(false)
stream_.close_parent_fds();
//Close the read end of the error pipe
close(err_rd_pipe);
subprocess_close(err_rd_pipe);
detail::Child chld(this, err_wr_pipe);
chld.execute_child();
}
else
{
close (err_wr_pipe);// close child side of pipe, else get stuck in read below
subprocess_close(err_wr_pipe);// close child side of pipe, else get stuck in read below
stream_.close_child_fds();
@ -1190,7 +1202,7 @@ inline void Popen::execute_process() noexcept(false)
fdopen(err_rd_pipe, "r"),
err_buf,
SP_MAX_ERR_BUF_SIZ);
close(err_rd_pipe);
subprocess_close(err_rd_pipe);
if (read_bytes || strlen(err_buf)) {
// Call waitpid to reap the child process
@ -1276,13 +1288,13 @@ namespace detail {
// Close the duped descriptors
if (stream.read_from_parent_ != -1 && stream.read_from_parent_ > 2)
close(stream.read_from_parent_);
subprocess_close(stream.read_from_parent_);
if (stream.write_to_parent_ != -1 && stream.write_to_parent_ > 2)
close(stream.write_to_parent_);
subprocess_close(stream.write_to_parent_);
if (stream.err_write_ != -1 && stream.err_write_ > 2)
close(stream.err_write_);
subprocess_close(stream.err_write_);
// Replace the current image with the executable
sys_ret = execvp(parent_->exe_name_.c_str(), parent_->cargv_.data());
@ -1309,15 +1321,15 @@ namespace detail {
#ifdef __USING_WINDOWS__
util::configure_pipe(&this->g_hChildStd_IN_Rd, &this->g_hChildStd_IN_Wr, &this->g_hChildStd_IN_Wr);
this->input(util::file_from_handle(this->g_hChildStd_IN_Wr, "w"));
this->write_to_child_ = _fileno(this->input());
this->write_to_child_ = subprocess_fileno(this->input());
util::configure_pipe(&this->g_hChildStd_OUT_Rd, &this->g_hChildStd_OUT_Wr, &this->g_hChildStd_OUT_Rd);
this->output(util::file_from_handle(this->g_hChildStd_OUT_Rd, "r"));
this->read_from_child_ = _fileno(this->output());
this->read_from_child_ = subprocess_fileno(this->output());
util::configure_pipe(&this->g_hChildStd_ERR_Rd, &this->g_hChildStd_ERR_Wr, &this->g_hChildStd_ERR_Rd);
this->error(util::file_from_handle(this->g_hChildStd_ERR_Rd, "r"));
this->err_read_ = _fileno(this->error());
this->err_read_ = subprocess_fileno(this->error());
#else
if (write_to_child_ != -1) input(fdopen(write_to_child_, "wb"));