[MSVCRT] Reimplement system/_wsystem

The new implementation is closely based on UCRT code and passes all tests for Vista+.

dll/win32/msvcrt/CMakeLists.txt

@@ -131,6 +131,7 @@ list(APPEND MSVCRT_SOURCE
     ${msvcrt_shared_asm}
     reactos/chkesp_failed.c
     reactos/misc.c
+    reactos/system.cpp
     concurrency.c
     console.c
     ctype.c

dll/win32/msvcrt/process.c

@@ -1245,6 +1245,7 @@ int CDECL _pclose(FILE* file)
   return i;
 }
 
+#ifndef __REACTOS__
 /*********************************************************************
  *      _wsystem (MSVCRT.@)
  *
@@ -1308,6 +1309,7 @@ int CDECL system(const char* cmd)
   }
   return res;
 }
+#endif
 
 /*********************************************************************
  *		_loaddll (MSVCRT.@)

dll/win32/msvcrt/reactos/system.cpp

@@ -0,0 +1,123 @@
+/*
+ * PROJECT:     ReactOS msvcrt
+ * LICENSE:     MIT (https://spdx.org/licenses/MIT)
+ * PURPOSE:     Implementation of system / _wsystem
+ * COPYRIGHT:   Copyright (c) Microsoft Corporation.  All rights reserved.
+ * COPYRIGHT:   Copyright 2025 Timo Kreuzer <[email protected]>
+ */
+
+#include <process.h>
+#include <io.h>
+#include <stdlib.h>
+#include <errno.h>
+
+extern "C" int _cdecl _access_s(const char* filename, int mode);
+extern "C" int _cdecl _waccess_s(const wchar_t* filename, int mode);
+
+int _cdecl _taccess_s(const char* filename, int mode)
+{
+    return _access_s(filename, mode);
+}
+
+int _cdecl _taccess_s(const wchar_t* filename, int mode)
+{
+    return _waccess_s(filename, mode);
+}
+
+char* __cdecl _tgetenv(_In_z_ char const* _VarName)
+{
+    return getenv(_VarName);
+}
+
+wchar_t* __cdecl _tgetenv(_In_z_ wchar_t const* _VarName)
+{
+    return _wgetenv(_VarName);
+}
+
+intptr_t __cdecl _tspawnve(int flags, const char* name, const char* const* argv,
+                        const char* const* envv)
+{
+    return _spawnve(flags, name, argv, envv);
+}
+
+intptr_t __cdecl _tspawnve(int flags, const wchar_t* name, const wchar_t* const* argv,
+                        const wchar_t* const* envv)
+{
+    return _wspawnve(flags, name, argv, envv);
+}
+
+intptr_t __cdecl _tspawnvpe(int flags, const char* name, const char* const* argv,
+                         const char* const* envv)
+{
+    return _spawnvpe(flags, name, argv, envv);
+}
+
+intptr_t __cdecl _tspawnvpe(int flags, const wchar_t* name, const wchar_t* const* argv,
+                         const wchar_t* const* envv)
+{
+    return _wspawnvpe(flags, name, argv, envv);
+}
+
+template <typename Character>
+static int __cdecl common_system(Character const* const command) throw()
+{
+    static Character const comspec_name[] = { 'C', 'O', 'M', 'S', 'P', 'E', 'C', '\0' }; // "COMSPEC"
+    static Character const cmd_exe[]      = { 'c', 'm', 'd', '.', 'e', 'x', 'e', '\0' }; // "cmd.exe"
+    static Character const slash_c[]      = { '/', 'c', '\0' }; // "/c"
+
+    Character const * comspec_value = _tgetenv(comspec_name);
+
+    // If the command is null, return TRUE only if %COMSPEC% is set and the file
+    // to which it points exists.
+    if (!command)
+    {
+        if (!comspec_value)
+            return 0;
+
+        return _taccess_s(comspec_value, 0) == 0;
+    }
+
+    Character const* arguments[4] =
+    {
+        comspec_value,
+        slash_c,
+        command,
+        nullptr
+    };
+
+    if (comspec_value)
+    {
+        errno_t const saved_errno = errno;
+        errno = 0;
+
+        int const result = static_cast<int>(_tspawnve(_P_WAIT, arguments[0], arguments, nullptr));
+        if (result != -1)
+        {
+            errno = saved_errno;
+            return result;
+        }
+
+        if (errno != ENOENT && errno != EACCES)
+        {
+            return result;
+        }
+
+        // If the error wasn't one of those two errors, try again with cmd.exe...
+        errno = saved_errno;
+    }
+
+   arguments[0] = cmd_exe;
+   return static_cast<int>(_tspawnvpe(_P_WAIT, arguments[0], arguments, nullptr));
+
+    return 0;
+}
+
+extern "C" int __cdecl system(char const* const command)
+{
+    return common_system(command);
+}
+
+extern "C" int __cdecl _wsystem(wchar_t const* const command)
+{
+    return common_system(command);
+}