libraries/SPI: abs -> std::abs and cast fixes #7362
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SPI library code erroneously assumed that: - abs() is a C function, so include stdlib.h is required. what happens instead is Arduino.h shadows `abs()` with it's own macro - uint32_t() - int32_t() promotes to int32_t, thus needing abs() Fix both issues, leaving existing calculations as-is.
devyte
requested changes
Jun 8, 2020
- restore abs call, cast freq to correctly display the intent - update magic numbers comments - move some spiclk_t magic numbers to func consts
mcspr
changed the title
devyte
approved these changes
Jun 9, 2020
earlephilhower
approved these changes
Jun 9, 2020
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Not to complicate comment chain in #6294 further
SPI library code erroneously assumed that
abs() is a C function, so include stdlib.h is required.what happens instead is Arduino.h shadows
abs()with it's own macrofreq - calFreqorfreq - bestFreqmay produce negative results and requireabs()In the referenced PR, when adding
using std::abs;it confuses GCC by introducing multiple functions named abs(), neither of which have uint32_t argument. As it turns out,uint32_t() - int32_t()promotes touint32_t, where old libc abs() silently converted it back tointFixing casts for
freqto explicitly make it a signed int when comparing with generated values, both of which are signed.edit: noting that abs() isn't a macro and we actually want signedness