Fix undefined reference to mag when USE_MAG isn't defined #9290
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The `mag` variable is defined as an `extern` in compass.h but the implementation in compass.c is bounded by `#ifdef USE_MAG`. So if `USE_MAG` is not debined then the `mag` variable is an undefined reference. In imu.c the `imuMahonyAHRSupdate()` function was being passed the elements of `mag` unconditionally like `mag.magADC[X]` so in the case that `USE_MAG` wasn't defined these were invalid null references. Luckily the logic in `imuMahonyAHRSupdate()` was properly bounded so that it never tried to access these variables. But in the case of a debug build the linker is unable to build a reference to these variables since they're never defined.
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I flagged as 4.2 since while it's technically a bug, it only affects people doing DEBUG builds and probably not needed to cherry-pick into 4.1 maintenance. But there's also no reason why it can't apply to 4.1 maintenance. Probably low risk either way. |
mikeller
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Dec 22, 2019
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Dec 22, 2019
Fix undefined reference to mag when USE_MAG isn't defined
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The
magvariable is defined as anexternin compass.h but the implementation in compass.c is bounded by#ifdef USE_MAG. So ifUSE_MAGis not defined then themagvariable is an undefined reference.In imu.c the
imuMahonyAHRSupdate()function was being passed the elements ofmagunconditionally likemag.magADC[X]so in the case thatUSE_MAGwasn't defined these were invalid null references. Luckily the logic inimuMahonyAHRSupdate()was properly bounded so that it never tried to access these variables. But in the case of a debug build the linker is unable to build a reference to these variables since they're never defined and the compile fails.Credit to @kmitchel for finding.