Use anonymous pipes for stdout/stderr redirection.

Closes #2444.

Avoid the overhead of creating and deleting temporary files.
Anonymous pipes have a limited buffer and require an active reader to
ensure the writer does not become blocked. Use a separate thread to
ensure the buffer does not get stuck full.

src/catch2/internal/catch_compiler_capabilities.hpp

@@ -37,6 +37,10 @@
 #    define CATCH_CPP17_OR_GREATER
 #  endif
 
+#  if (__cplusplus >= 202002L) || (defined(_MSVC_LANG) && _MSVC_LANG >= 202002L)
+#    define CATCH_CPP20_OR_GREATER
+#  endif
+
 #endif
 
 // Only GCC compiler should be used in this block, so other compilers trying to

src/catch2/internal/catch_output_redirect.cpp

@@ -14,13 +14,16 @@
 #include <sstream>
 
 #if defined(CATCH_CONFIG_NEW_CAPTURE)
+    #include <system_error>
     #if defined(_MSC_VER)
-    #include <io.h>      //_dup and _dup2
+    #include <fcntl.h> // _O_TEXT
+    #include <io.h> // _close, _dup, _dup2, _fileno, _pipe and _read
+    #define close _close
     #define dup _dup
     #define dup2 _dup2
     #define fileno _fileno
     #else
-    #include <unistd.h>  // dup and dup2
+    #include <unistd.h> // close, dup, dup2, fileno, pipe and read
     #endif
 #endif
 
@@ -60,85 +63,202 @@ namespace Catch {
 
 #if defined(CATCH_CONFIG_NEW_CAPTURE)
 
-#if defined(_MSC_VER)
-    TempFile::TempFile() {
-        if (tmpnam_s(m_buffer)) {
-            CATCH_RUNTIME_ERROR("Could not get a temp filename");
-        }
-        if (fopen_s(&m_file, m_buffer, "w+")) {
-            char buffer[100];
-            if (strerror_s(buffer, errno)) {
-                CATCH_RUNTIME_ERROR("Could not translate errno to a string");
-            }
-            CATCH_RUNTIME_ERROR("Could not open the temp file: '" << m_buffer << "' because: " << buffer);
-        }
+inline void close_or_throw(int descriptor)
+{
+    if (close(descriptor))
+    {
+        throw std::system_error{ errno, std::generic_category() };
     }
-#else
-    TempFile::TempFile() {
-        m_file = std::tmpfile();
-        if (!m_file) {
-            CATCH_RUNTIME_ERROR("Could not create a temp file.");
-        }
+}
+
+inline int dup_or_throw(int descriptor)
+{
+    int result{ dup(descriptor) };
+
+    if (result == -1)
+    {
+        throw std::system_error{ errno, std::generic_category() };
+    }
+
+    return result;
+}
+
+inline int dup2_or_throw(int sourceDescriptor, int destinationDescriptor)
+{
+    int result{ dup2(sourceDescriptor, destinationDescriptor) };
+
+    if (result == -1)
+    {
+        throw std::system_error{ errno, std::generic_category() };
     }
 
+    return result;
+}
+
+inline int fileno_or_throw(std::FILE* file)
+{
+    int result{ fileno(file) };
+
+    if (result == -1)
+    {
+        throw std::system_error{ errno, std::generic_category() };
+    }
+
+    return result;
+}
+
+inline void pipe_or_throw(int descriptors[2])
+{
+#if defined(_MSC_VER)
+    constexpr int defaultPipeSize{ 0 };
+
+    int result{ _pipe(descriptors, defaultPipeSize, _O_TEXT) };
+#else
+    int result{ pipe(descriptors) };
 #endif
 
-    TempFile::~TempFile() {
-         // TBD: What to do about errors here?
-         std::fclose(m_file);
-         // We manually create the file on Windows only, on Linux
-         // it will be autodeleted
+    if (result)
+    {
+        throw std::system_error{ errno, std::generic_category() };
+    }
+}
+
+inline int read_or_throw(int descriptor, void* buffer, size_t size)
+{
 #if defined(_MSC_VER)
-         std::remove(m_buffer);
+    int result{ _read(descriptor, buffer, static_cast<unsigned>(size)) };
+#else
+    int result{ read(descriptor, buffer, size) };
 #endif
+
+    if (result == -1)
+    {
+        throw std::system_error{ errno, std::generic_category() };
     }
 
+    return result;
+}
 
-    FILE* TempFile::getFile() {
-        return m_file;
+inline void fflush_or_throw(std::FILE* file)
+{
+    if (std::fflush(file))
+    {
+        throw std::system_error{ errno, std::generic_category() };
     }
+}
 
-    std::string TempFile::getContents() {
-        std::stringstream sstr;
-        char buffer[100] = {};
-        std::rewind(m_file);
-        while (std::fgets(buffer, sizeof(buffer), m_file)) {
-            sstr << buffer;
-        }
-        return sstr.str();
+jthread::jthread() noexcept : m_thread{} {}
+
+template <typename F, typename... Args>
+jthread::jthread(F&& f, Args&&... args) : m_thread{ std::forward<F>(f), std::forward<Args>(args)... } {}
+
+// Not exactly like std::jthread, but close enough for the code below.
+jthread::~jthread() noexcept
+{
+    if (m_thread.joinable())
+    {
+        m_thread.join();
     }
+}
+
+constexpr UniqueFileDescriptor::UniqueFileDescriptor() noexcept : m_value{} {}
 
-    OutputRedirect::OutputRedirect(std::string& stdout_dest, std::string& stderr_dest) :
-        m_originalStdout(dup(1)),
-        m_originalStderr(dup(2)),
-        m_stdoutDest(stdout_dest),
-        m_stderrDest(stderr_dest) {
-        dup2(fileno(m_stdoutFile.getFile()), 1);
-        dup2(fileno(m_stderrFile.getFile()), 2);
+UniqueFileDescriptor::UniqueFileDescriptor(int value) noexcept : m_value{ value } {}
+
+constexpr UniqueFileDescriptor::UniqueFileDescriptor(UniqueFileDescriptor&& other) noexcept :
+    m_value{ other.m_value }
+{
+    other.m_value = 0;
+}
+
+UniqueFileDescriptor::~UniqueFileDescriptor() noexcept
+{
+    if (m_value == 0)
+    {
+        return;
     }
 
-    OutputRedirect::~OutputRedirect() {
-        Catch::cout() << std::flush;
-        fflush(stdout);
-        // Since we support overriding these streams, we flush cerr
-        // even though std::cerr is unbuffered
-        Catch::cerr() << std::flush;
-        Catch::clog() << std::flush;
-        fflush(stderr);
+    close_or_throw(m_value); // std::terminate on failure (due to noexcept)
+}
 
-        dup2(m_originalStdout, 1);
-        dup2(m_originalStderr, 2);
+UniqueFileDescriptor& UniqueFileDescriptor::operator=(UniqueFileDescriptor&& other) noexcept
+{
+    if (this != &other)
+    {
+        if (m_value != 0)
+        {
+            close_or_throw(m_value); // std::terminate on failure (due to noexcept)
+        }
 
-        m_stdoutDest += m_stdoutFile.getContents();
-        m_stderrDest += m_stderrFile.getContents();
+        m_value = other.m_value;
+        other.m_value = 0;
     }
 
+    return *this;
+}
+
+constexpr int UniqueFileDescriptor::get() { return m_value; }
+
+inline void create_pipe(UniqueFileDescriptor& readDescriptor, UniqueFileDescriptor& writeDescriptor)
+{
+    readDescriptor = {};
+    writeDescriptor = {};
+
+    int descriptors[2];
+    pipe_or_throw(descriptors);
+
+    readDescriptor = UniqueFileDescriptor{ descriptors[0] };
+    writeDescriptor = UniqueFileDescriptor{ descriptors[1] };
+}
+
+inline void read_thread(UniqueFileDescriptor&& file, std::string& result)
+{
+    std::string buffer{};
+    constexpr size_t bufferSize{ 4096 };
+    buffer.resize(bufferSize);
+    size_t sizeRead{};
+
+    while ((sizeRead = read_or_throw(file.get(), &buffer[0], bufferSize)) != 0)
+    {
+        result.append(buffer.data(), sizeRead);
+    }
+}
+
+OutputFileRedirector::OutputFileRedirector(FILE* file, std::string& result) :
+    m_file{ file },
+    m_fd{ fileno_or_throw(m_file) },
+    m_previous{ dup_or_throw(m_fd) }
+{
+    fflush_or_throw(m_file);
+
+    UniqueFileDescriptor readDescriptor{};
+    UniqueFileDescriptor writeDescriptor{};
+    create_pipe(readDescriptor, writeDescriptor);
+
+    // Anonymous pipes have a limited buffer and require an active reader to ensure the writer does not become blocked.
+    // Use a separate thread to ensure the buffer does not get stuck full.
+    m_readThread = jthread{ [readDescriptor{ std::move(readDescriptor) }, &result] () mutable {
+        read_thread(std::move(readDescriptor), result); } };
+
+    dup2_or_throw(writeDescriptor.get(), m_fd);
+}
+
+OutputFileRedirector::~OutputFileRedirector() noexcept
+{
+    fflush_or_throw(m_file); // std::terminate on failure (due to noexcept)
+    dup2_or_throw(m_previous.get(), m_fd); // std::terminate on failure (due to noexcept)
+}
+
+OutputRedirect::OutputRedirect(std::string& output, std::string& error) :
+    m_output{ stdout, output }, m_error{ stderr, error } {}
+
 #endif // CATCH_CONFIG_NEW_CAPTURE
 
 } // namespace Catch
 
 #if defined(CATCH_CONFIG_NEW_CAPTURE)
     #if defined(_MSC_VER)
+    #undef close
     #undef dup
     #undef dup2
     #undef fileno