How to wrap an existing library in a custom namespace to avoid redeclaration error?

Using Arduino Programming Questions
1

Dear community,

I have a namespace related issue, which I am unable to solve, even with Dr. Google, as I am not familiar with namespaces at all.

With my latest project, I would like to use the following two libraries (installed latest version via library manager) in a sketch running on an Arduino Nano:

  • INA219_WE (voltage and current sensor readout)
  • Low-Power (save some power in between sensor readouts)

Both libraries work well independently.

However, if I import both libraries in the same sketch, I get a redeclaration error:

Sketch

#include <INA219_WE.h>
#include <LowPower.h>

void setup() {
}

void loop() {
}

Error

In file included from <...>\libraryConflictExample\libraryConflictExample.ino:2:0:
<...>\Arduino\libraries\Low-Power/LowPower.h:29:2: error: redeclaration of 'ADC_OFF'
  ADC_OFF,
  ^~~~~~~
In file included from <...>\libraryConflictExample\libraryConflictExample.ino:1:0:
<...>\Arduino\libraries\INA219_WE\src/INA219_WE.h:59:5: note: previous declaration 'INA219_MEASURE_MODE ADC_OFF'
     ADC_OFF         = 0b00000100,
     ^~~~~~~

As the error message indicates, both libraries use the constant ADC_OFF. A similar problem was discussed for different libraries. There, the author fixed the problem by modifying one of the libraries. For compatibility reasons I would like to avoid changing the (external) library code.

In the aforementioned thread @PieterP suggested to "wrap all library code in a namespace".

So what I tried is this:

#include <INA219_WE.h>
namespace LoPo {
  #include <LowPower.h>
}

void setup() {
}

void loop() {
  LoPo::LowPower.idle(LoPo::SLEEP_8S, LoPo::ADC_OFF, LoPo::TIMER2_OFF, LoPo::TIMER1_OFF, LoPo::TIMER0_OFF, 
                      LoPo::SPI_OFF, LoPo::USART0_OFF, LoPo::TWI_OFF);
}

For the library import this works fine, but the function call raises an error:

<...>\AppData\Local\Temp\ccbloPUo.ltrans0.ltrans.o: In function `loop':
<...>\Arduino\libraryConflictExample/libraryConflictExample.ino:10: undefined reference to `LoPo::LowPower'
<...>\Arduino\libraryConflictExample/libraryConflictExample.ino:10: undefined reference to `LoPo::LowPower'
<...>\Arduino\libraryConflictExample/libraryConflictExample.ino:10: undefined reference to `LoPo::LowPowerClass::idle(LoPo::period_t, LoPo::adc_t, LoPo::timer2_t, LoPo::timer1_t, LoPo::timer0_t, LoPo::spi_t, LoPo::usart0_t, LoPo::twi_t)'
collect2.exe: error: ld returned 1 exit status

Hence, I was wondering: Is it possible to wrap the entire contents of a library including function calls in a namespace without touching the external library code? And if yes, how would I do this?

Any help would be appreciated,
Max

2

As a new user I am apparently not allowed to add more than two links in a post (weird restriction).
Hence, here the links to the library codes:

  • INA219_WE (voltage and current sensor readout)
  • Low-Power (save some power in between sensor readouts)
3

That's not what I meant, you need to edit the library source files and add the namespaces there, wrapping the header won't work.

Did you try the enum class solution I mentioned in the other thread?

4

Wow, that was quick!

Based on your answer I now tried to change the LowPower.h: (Is this what you meant?)
old

enum adc_t
{
	ADC_OFF,
	ADC_ON
};

new

enum class adc_t
{
	ADC_OFF,
	ADC_ON
};

Sketch

#include <INA219_WE.h>
#include <LowPower.h>

void setup() {
}

void loop() {
  LowPower.idle(SLEEP_8S, ADC_OFF, TIMER2_OFF, TIMER1_OFF, TIMER0_OFF, 
                      SPI_OFF, USART0_OFF, TWI_OFF);
}

This results in a conversion error:

no known conversion for argument 2 from 'INA219_MEASURE_MODE' to 'adc_t'

Hence, I suspect I have to use ADC_OFF differently in the function call. Can you help?

I was still hoping for a solution without touching the library code, if there is any. Otherwise, I could simply rename the constant in one of the libraries.

EDIT:
OK, it seems I have to change it to adc_t::ADC_OFF
Unfortunately this results in multiple 'ADC_OFF' was not declared in this scope errors. I suspect this is because the author of LowPower.h does not actually assign values to the library's constants. At least I was not able to find any in the git repo. -> I will try editing the other library instead.

5

You have to change this in the library itself as well.
Assigning values is not necessary.

6

OK, thanks for the help.

Remains the question: Is there any way (maybe not namespace but a different approach), which could leave the external libraries untouched?

7

Another option is to not use the low power library , and use Google to find the code to put your device to sleep without it .

1 Like
8

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