Merge branch 'feature/cpp_exceptions_example' into 'master'

examples: add C++ exception handling example

See merge request idf/esp-idf!3178
This commit is contained in:
Ivan Grokhotkov 2018-09-07 10:34:18 +08:00
commit 8893438f08
7 changed files with 142 additions and 0 deletions

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@ -119,4 +119,5 @@ Enabling exception handling normally increases application binary size by a few
If an exception is thrown, but there is no ``catch`` block, the program will be terminated by ``abort`` function, and backtrace will be printed. See :doc:`Fatal Errors <fatal-errors>` for more information about backtraces.
See :example:`system/cpp_exceptions` for an example of C++ exception handling.

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#
# This is a project Makefile. It is assumed the directory this Makefile resides in is a
# project subdirectory.
#
PROJECT_NAME := cpp_exceptions_example
include $(IDF_PATH)/make/project.mk

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# Example: C++ exception handling
(See the README.md file in the upper level 'examples' directory for more information about examples.)
This example demonstrates usage of C++ exceptions in ESP-IDF.
By default, C++ exceptions support is disabled in ESP-IDF. It can be enabled using `CONFIG_CXX_EXCEPTIONS` configuration option.
In this example, `sdkconfig.defaults` file sets `CONFIG_CXX_EXCEPTIONS` option. This enables both compile time support (`-fexceptions` compiler flag) and run-time support for C++ exception handling.
Example source code declares a class which can throw exception from the constructor, depending on the argument. It illustrates that exceptions can be thrown and caught using standard C++ facilities.
## How to use example
### Configure the project
Run `make menuconfig` and set serial port under Serial Flasher Options.
### Build and Flash
Build the project and flash it to the board, then run monitor tool to view serial output:
```
make -j4 flash monitor
```
(To exit the serial monitor, type ``Ctrl-]``.)
See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.
## Example Output
```
app_main starting
In constructor, arg=42
In constructor, arg=0
In destructor, m_arg=42
Exception caught: Exception in constructor
app_main done
```

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from __future__ import print_function
import os
import sys
test_fw_path = os.getenv('TEST_FW_PATH')
if test_fw_path and test_fw_path not in sys.path:
sys.path.insert(0, test_fw_path)
import TinyFW
import IDF
@IDF.idf_example_test(env_tag='Example_WIFI')
def test_examples_system_cpp_exceptions(env, extra_data):
dut = env.get_dut('cpp_exceptions_example', 'examples/system/cpp_exceptions')
# start test
dut.start_app()
lines = ['app_main starting',
'In constructor, arg=42',
'In constructor, arg=0',
'In destructor, m_arg=42',
'Exception caught: Exception in constructor',
'app_main done'
]
for line in lines:
dut.expect(line, timeout=2)
if __name__ == '__main__':
test_examples_system_cpp_exceptions()

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#
# "main" pseudo-component makefile.
#
# (Uses default behaviour of compiling all source files in directory, adding 'include' to include path.)

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/* C++ exception handling example
This example code is in the Public Domain (or CC0 licensed, at your option.)
Unless required by applicable law or agreed to in writing, this
software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
CONDITIONS OF ANY KIND, either express or implied.
*/
#include <iostream>
using std::cout;
using std::endl;
using std::runtime_error;
/* A simple class which may throw an exception from constructor */
class Throwing
{
public:
Throwing(int arg)
: m_arg(arg)
{
cout << "In constructor, arg=" << arg << endl;
if (arg == 0) {
throw runtime_error("Exception in constructor");
}
}
~Throwing()
{
cout << "In destructor, m_arg=" << m_arg << endl;
}
protected:
int m_arg;
};
/* Inside .cpp file, app_main function must be declared with C linkage */
extern "C" void app_main()
{
cout << "app_main starting" << endl;
try {
/* This will succeed */
Throwing obj1(42);
/* This will throw an exception */
Throwing obj2(0);
cout << "This will not be printed" << endl;
} catch (const runtime_error &e) {
cout << "Exception caught: " << e.what() << endl;
}
cout << "app_main done" << endl;
}

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# Enable C++ exceptions and set emergency pool size for exception objects
CONFIG_CXX_EXCEPTIONS=y
CONFIG_CXX_EXCEPTIONS_EMG_POOL_SIZE=1024