Use std::abs for a float-compatible abs() function #2738
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* Other Arduino cores uses a macro to redefine libc abs() to take any type, meaning abs(-3.3) == 3.3 not the normal libc result of 3. * 1e4bf14 (espressif#1783) replaced similar min, max macros with c++ stdlib. However this change includes <algorithm> after the line which defines the abs() macro. <algorithm> includes <cstdlib> which undefines abs() and re-defines it. * This means abs() becomes the plain libc version again which only takes integers, so abs(-3.3) == 3. As reported here: espressif/esp-idf#3405 This fix tries to keep in the spirit of espressif#1783 by using libstdc++. The other option would be to include <cstdlib> before defining the abs() macro, so it doesn't get undef-ed again later on.
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@projectgus My apologies. I deleted my last comment, as I wrongly assumed that the change to using the standard library wouldn't work with floats. |
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@martinl1 No worries, I oversimplified a long story in the PR summary so it's not immediately clear to someone who hasn't followed the whole saga. :) I edited it a bit to try and make it clearer what this change does, vs what was a regression in earlier changes. |
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This has been PITA for a loong time. As far as I remember, we have tried this before and libraries broke. |
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Other Arduino cores uses a macro to redefine libc abs() to take any type, meaning
abs(-3.3) == 3.3not the normal libc result of 3.1e4bf14 (cores: replace max and min macros with imports from std #1783) replaced similar
min,maxmacros with c++ stdlib. However this change includes<algorithm>after the line which defines the abs() macro.<algorithm>includes<cstdlib>which undefinesabs()and re-defines it.As a result, current esp32 Arduino core has a bug compared to other Arduino cores:
abs()is now the plain libc version which only takes integers, soabs(-3.3) == 3. As reported here: float computations (fp32, fp64) evaluate differently vs. ARM Cortex M0+M3+M4 & Mega2560 (IDFGH-1084) esp-idf#3405This fix tries to keep in the spirit of #1783 by using libstdc++ rather than a macro, for the same effect (abs can take any compatible type). The other option would be to include
<cstdlib>before defining theabs()macro, so it doesn't get undef-ed again later on.This will probably also fix #2128 as the
abs()macro is no longer defined.