odr | Optical Document Recognition | Computer Vision library

It can be included in multiple compilation units. If you mark the definition inline it should be happy.

This is what I meant with this comment

though boost::system::system_error could invite issues back

The trouble is, error categories are global singleton instances, with object identity (i.e. compared for equality by their address).

You'r ending up with multiple instances in multiple modules. The usual solution is to

• dynamically link to Boost System, so all libraries use the same copy (this does however sometimes run into initialization order issues)
• if that doesn't solve it, make sure all modules actually load the same library (version?)
• In recent boosts I think there's the option to build Boost System completely header-only. This may or may not involve new-fangled C++14 inline, I haven't checked.

If all else fails, do your own translation. There's related issues that might give you ideas:

• Is it possible to convert a boost::system::error_code to a std:error_code?
• Do note that exceptions may run into very similar issues due to RTTI not necessarily matching; exceptions need to be exported types and linked dynamically from the same module for the exception handlers to match the thrown runtime type id.

Is it normal or expected to compare only errorCode.value() against enums?

No it is not. According to some sources Boost as well as standard library promise to map generic error category to errc which is standard - so you could do that, but you still have to figure out whether that is the category, so doesn't help your scenario.

Is it possible for cmake to set an environment variable so it persists after cmake runs?

No. This is not possible. You cannot set an environment variable in the parent process from CMake. The documentation for the set command even cautions you about this.

From here:

This command affects only the current CMake process, not the process from which CMake was called, nor the system environment at large, nor the environment of subsequent build or test processes.

However, you might be able to work around this particular issue via the CMAKE_CXX_COMPILER_LAUNCHER variable:

Normally, a class definition goes in an ".h" file and its member functions' definitions go in a ".cpp" file.

If you want to define member functions in the header, you need to either declare them inline, or write them inside the class definition (which makes them implicitly inline).

We can create a sequence grouped by the 'id' columns and then with pivot_wider reshape to wide

std::bad_alloc is often thrown when there is not enough memory to be allocated. I can't say if this will solve the problem, but your repeated allocations and deallocations of objects are both unnecessary and harmful (causing memory fragmentation).

Instead of

In the uVision project configuration dialog C/C++ tab, select "use C99".

ISO C90 dies not allow declaration of variables in either a for statement or following non -declaritive code in a statement block.

Alternatively move the declaration to the top of the statement block in which it is required. Better to use C99 though - it has been around long enough to be regarded as lowest common denominator standard I think!

Based on the info that you have the LED on PC13, I assume you're using the famous Blue Pill board. In that board, LED connection is inverted because of the special limitations of PC13 - that pin should only sink current, not source. So, in order to turn it on, you need to write 0 to corresponding bit of ODR.

Normally, I'm against the usage of magic numbers. But for STM32F103, using hex literals for GPIO configuration is practical, because one single hex digit uniquely defines the pin mode. One can memorize the meaning of hex literals for GPIO settings, and use them in a compact assignment which defines the 8 pins of a GPIO port at once. If you make GPIO configurations only once, you don't need &= or |= operators.

Also, prefer using BSRR instead of ODR, because it allows atomic modification of output pins.

Here is a LED blink example for Blue Pill board:

If you configure the output to be PUSH/PULL, adding a PULLDOWN resistor will divide the output voltage over the resistor. Do not use PU/PD resistors with PP, because it is always driven and doesn't need a PU/PD.