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70 lines
2.2 KiB
Markdown
70 lines
2.2 KiB
Markdown
# Example: C++ run-time type info (RTTI)
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(See the README.md file in the upper level 'examples' directory for more information about examples.)
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This example demonstrates usage of the RTTI feature in ESP-IDF.
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By default, RTTI support is disabled in ESP-IDF. It can be enabled using `CONFIG_COMPILER_CXX_RTTI` configuration option.
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In this example, `sdkconfig.defaults` file sets `CONFIG_COMPILER_CXX_RTTI` option. This enables compile time support for RTTI (`-frtti` compiler flag).
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The example prints demangled type names of a few objects and functions, obtained from `typeinfo().name`. The example also generates several objects of two classes, derived from a common base class. For each object, it is demonstrated that `dynamic_cast` behaves as expected, returning non-NULL when casting to the real object type, and NULL when casting to a different type.
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## How to use example
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### Configure the project
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To run this example, no additional configuration is necessary.
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### Build and Flash
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Build the project and flash it to the board, then run monitor tool to view serial output:
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```
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idf.py -p PORT flash monitor
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```
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(Replace PORT with the name of the serial port to use.)
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(To exit the serial monitor, type ``Ctrl-]``.)
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See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.
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## Example Output
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```
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Type names of a few objects:
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Type name of std::cout is: std::ostream
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Type name of std::cin is: std::istream
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Type of app_main is: void ()
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Type name of a lambda function is: app_main::{lambda(int, int)#1}
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Generating 5 random objects and printing their types:
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obj->name() is: DerivedB
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typeid(*obj).name() is: DerivedB
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dynamic_cast<DerivedA*>(obj)=0
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dynamic_cast<DerivedB*>(obj)=0x3ffb7e88
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obj->name() is: DerivedB
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typeid(*obj).name() is: DerivedB
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dynamic_cast<DerivedA*>(obj)=0
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dynamic_cast<DerivedB*>(obj)=0x3ffb7e9c
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obj->name() is: DerivedA
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typeid(*obj).name() is: DerivedA
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dynamic_cast<DerivedA*>(obj)=0x3ffb7eb0
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dynamic_cast<DerivedB*>(obj)=0
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obj->name() is: DerivedB
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typeid(*obj).name() is: DerivedB
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dynamic_cast<DerivedA*>(obj)=0
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dynamic_cast<DerivedB*>(obj)=0x3ffb7ec4
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obj->name() is: DerivedA
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typeid(*obj).name() is: DerivedA
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dynamic_cast<DerivedA*>(obj)=0x3ffb7ed8
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dynamic_cast<DerivedB*>(obj)=0
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Example finished.
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```
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