nx_metadata_sdk 1.0 Metadata SDK

Public Member Functions | Static Public Member Functions | Static Protected Member Functions | List of all members
nx::kit::OutputRedirector Class Reference

`#include <output_redirector.h>`

Inheritance diagram for nx::kit::OutputRedirector:

## Public Member Functions
| OutputRedirector (const OutputRedirector &)=delete
void | operator= (const OutputRedirector &)=delete

## Static Public Member Functions
static const OutputRedirector & | getInstance ()
static void | ensureOutputRedirection ()

## Static Protected Member Functions
static void | redirectStdoutAndStderrIfNeeded (const char *overridingLogFilesDir=nullptr)

## Detailed Description

The mechanism allows to perform output (stdout, stderr) redirection to files.

To activate redirection, the user must create special files in the directory nx::kit::IniConfig::iniFilesDir(), named as follows: `<executable-name-without-extension>_stdout.log` and/or `<executable-name-without-extension>_stderr.log`

If such a file exists, the respective stream will be appended to the file contents.

Redirection is performed during static initialization, thus, to ensure that it occurs before any other output, this library should be the first in the list of linked libraries of the executable. Note that in Windows due to some MSVC C++ Runtime issues, if any output occurs before the redirection, the redirection may not work (the output disappears at all).

If needed, this mechanism can be disabled defining a macro at compiling output_redirector.cpp: -DNX_OUTPUT_REDIRECTOR_DISABLED.

ATTENTION: If all of the following conditions are met:

1. The shared library is built on Windows as "Debug" with MSVC.
2. The library is loaded dynamically in runtime.
3. The main executable runs as a Windows service. Then the redirected output doesn't go to the file and just disappears. This behavior is due to some unknown MSVC issue.

## Member Function Documentation

## ◆ ensureOutputRedirection()

void nx::kit::OutputRedirector::ensureOutputRedirection | ( |  | ) |
| static

Call from anywhere in the code of the executable that links with this library.

This is needed to guarantee that the static initializer in this library (that performs the redirection) is called, because if no symbols from this library are used in the executable, the linker can optimize away any static initialization in this library.

ATTENTION: This call should be done exactly once to prevent unexpected behavior in the case when more than one copy of the library is linked to the executable. This situation can occur, for example, when one copy of nx::kit library is linked to the executable itself, and another one is linked to the shared library. If ensureOutputRedirection() is called once (in the executable) this works perfectly well, because the linker leaves static initilization in the executable and optimizes it away from the shared library. Otherwise (ensureOutputRedirection() is called both in the executable and in the shared library) it can result in multiple initialization of the Redirector, and some output can be lost.

The documentation for this class was generated from the following files:

- nx_kit/src/nx/kit/output_redirector.h
- nx_kit/src/nx/kit/output_redirector.cpp