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system: Add support for accessing system error information.
Add the following LCB syntax: - `reset system error`: Reset system code to "none" (i.e. 0) - `the system error code`: The current numerical error code - `the system error message`: A string describing the current error code.
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‎docs/lcb/notes/feature-system_error.md‎

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# LiveCode Builder Standard Library
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## System error information
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* Two new expressions have been added for accessing platform-specific
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system error status:
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* `the system error code` evaluates to the current numerical system
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error code
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* `the system error message` evaluates to a string describing the
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current system error
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* The new `reset system error` statement clears the current system
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error.
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‎libfoundation/include/foundation-system.h‎

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/* -*-c++-*-
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Copyright (C) 2015 LiveCode Ltd.
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Copyright (C) 2015-2016 LiveCode Ltd.
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This file is part of LiveCode.
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@@ -33,6 +33,7 @@ extern "C" {
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#include <system-library.h>
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#include <system-random.h>
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#include <system-stream.h>
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#include <system-error.h>
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}
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‎libfoundation/include/system-error.h‎

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/* -*-c++-*-
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Copyright (C) 2016 LiveCode Ltd.
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This file is part of LiveCode.
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LiveCode is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License v3 as published by the Free
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Software Foundation.
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LiveCode is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with LiveCode. If not see <http://www.gnu.org/licenses/>. */
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#if !defined(__MCS_SYSTEM_H_INSIDE__)
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# error "Only <foundation-system.h> can be included directly"
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#endif
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/* ================================================================
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* System error handling
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* ================================================================ */
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/* The MCSError library provides an API for accessing and resetting
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* the system error status. This is to support standardized use of
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* the POSIX and Win32 APIs.
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*/
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/* Reset or clear the current system error state. */
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MC_DLLEXPORT void MCSErrorReset (void);
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/* Get the platform-dependent numeric code corresponding to the
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* current system error. */
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MC_DLLEXPORT uint32_t MCSErrorGetCode (void);
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/* Get a platform-dependent string describing a system error code. */
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MC_DLLEXPORT bool MCSErrorGetDescription (uint32_t p_code, MCStringRef& r_description);

‎libfoundation/libfoundation.gyp‎

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'include/foundation-text.h',
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'include/foundation-unicode.h',
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'include/system-commandline.h',
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'include/system-error.h',
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'include/system-file.h',
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'include/system-init.h',
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'include/system-library.h',
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'src/foundation-objc.mm',
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'src/foundation-ffi-js.cpp',
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'src/system-commandline.cpp',
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'src/system-error.cpp',
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'src/system-file.cpp',
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'src/system-file-posix.cpp',
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'src/system-file-w32.cpp',

‎libfoundation/src/system-error.cpp‎

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/* -*-c++-*-
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Copyright (C) 2016 LiveCode Ltd.
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This file is part of LiveCode.
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LiveCode is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License v3 as published by the Free
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Software Foundation.
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LiveCode is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with LiveCode. If not see <http://www.gnu.org/licenses/>. */
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#include "system-private.h"
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#include <foundation-auto.h>
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#if defined(__WINDOWS__)
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/* ================================================================
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* Windows implementations
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* ================================================================ */
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# include <windows.h>
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MC_DLLEXPORT_DEF void
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MCSErrorReset ()
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{
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SetLastError (0);
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}
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MC_DLLEXPORT_DEF uint32_t
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MCSErrorGetCode ()
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{
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return GetLastError ();
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}
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MC_DLLEXPORT_DEF bool
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MCSErrorGetDescription (uint32_t p_code,
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MCStringRef& r_description)
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{
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DWORD t_code = GetLastError ();
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/* No error has been recorded */
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if (0 == t_code)
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{
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return MCStringCopy (kMCEmptyString, r_description);
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}
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LPWSTR t_message_buffer = nil;
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DWORD t_message_len = FormatMessageW (
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(FORMAT_MESSAGE_ALLOCATE_BUFFER |
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FORMAT_MESSAGE_FROM_SYSTEM |
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FORMAT_MESSAGE_IGNORE_INSERTS), /* dwFlags */
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nil, /* lpSource */
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t_code, /* dwMessageId */
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MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), /* dwLanguageId */
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reinterpret_cast<LPWSTR>(&t_message_buffer), /* lpBuffer */
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0, /* nSize */
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nil); /* arguments... */
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bool t_success = true;
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MCAutoStringRef t_description;
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if (t_success)
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t_success = MCStringCreateWithChars(t_message_buffer,
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t_message_len,
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&t_description);
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LocalFree(t_message_buffer);
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return MCStringCopy(*t_description, r_description);
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}
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#else /* !__WINDOWS__ */
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/* ================================================================
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* POSIX implementations
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* ================================================================ */
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#include <errno.h>
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MC_DLLEXPORT_DEF void
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MCSErrorReset ()
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{
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errno = 0;
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}
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MC_DLLEXPORT_DEF uint32_t
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MCSErrorGetCode ()
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{
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return errno;
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}
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MC_DLLEXPORT_DEF bool
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MCSErrorGetDescription (uint32_t p_code,
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MCStringRef& r_description)
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{
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return MCStringCreateWithCString(strerror(p_code),
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r_description);
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}
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#endif /* !__WINDOWS__ */

‎libscript/src/module-system.cpp‎

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/* -*-c++-*-
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Copyright (C) 2015 LiveCode Ltd.
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Copyright (C) 2015-2016 LiveCode Ltd.
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This file is part of LiveCode.
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/* UNCHECKED */ MCSCommandLineGetArguments (r_list);
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}
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/* ================================================================
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* System error information
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* ================================================================ */
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extern "C" MC_DLLEXPORT_DEF void
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MCSystemEvalErrorCode (uint32_t & r_code)
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{
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r_code = MCSErrorGetCode ();
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}
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extern "C" MC_DLLEXPORT_DEF void
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MCSystemEvalErrorDescription (MCStringRef & r_string)
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{
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/* UNCHECKED */ MCSErrorGetDescription (MCSErrorGetCode (), r_string);
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}
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////////////////////////////////////////////////////////////////
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extern "C" bool com_livecode_system_Initialize (void)

‎libscript/src/system.lcb‎

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/*
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Copyright (C) 2015 LiveCode Ltd.
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Copyright (C) 2015-2016 LiveCode Ltd.
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This file is part of LiveCode.
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MCSystemExecGetCommandArguments(output)
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end syntax
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----------------------------------------------------------------
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-- System error information
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----------------------------------------------------------------
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public foreign handler MCSErrorReset() returns nothing binds to "<builtin>"
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public foreign handler MCSystemEvalErrorCode(out Code as UInt32) returns nothing binds to "<builtin>"
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public foreign handler MCSystemEvalErrorDescription(out Description as String) returns nothing binds to "<builtin>"
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/**
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Summary: Clear the system error code.
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Description:
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Reset the system error code to its platform-dependent default ("no
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error") value.
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Tags: System
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*/
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syntax ResetSystemError is statement
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"reset" "system" "error"
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begin
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MCSErrorReset()
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end syntax
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/**
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Summary: The system error code.
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Description:
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Evaluates to the current platform-dependent system error code.
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- On Windows, returns the result of `GetLastError()`.
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- On other platforms, returns the current value of `errno`.
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> **Note:** The system error code may be modified or cleared by any
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> syntax that interacts with the operating system (e.g. by performing
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> input or output). You should check the system error code as soon as
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> possible after any platform operation that might fail.
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Related: SystemErrorDescription
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Tags: System
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*/
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syntax SystemErrorCode is expression
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"the" "system" "error" "code"
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begin
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MCSystemEvalErrorCode(output)
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end syntax
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/**
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Summary: The system error description.
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Description:
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Evaluates to a string describing the current platform-dependent system
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error code.
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> **Note:** The system error code may be modified or cleared by any
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> syntax that interacts with the operating system (e.g. by performing
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> input or output). You should check the system error code as soon as
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> possible after any platform operation that might fail.
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Related: SystemErrorCode
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Tags: System
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*/
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syntax SystemErrorDescription is expression
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"the" "system" "error" "message"
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begin
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MCSystemEvalErrorDescription(output)
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end syntax
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--
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end module

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