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work around test failure on ARM float min/max roundtrip to&from string in JSON parsing #9

Closed spoonincode closed 2 years ago

spoonincode commented 2 years ago

On ARM Linux, even with latest gcc12, strtof() is returning an out of range error when being fed the string output from fpconv_dtoa() for a std::numeric_limits<float>::min(). This leads to a unit test failure on ARM Linux builds. I am so far unable to come up with a good solution here. Barring writing or integrating a custom string-to-float impl, the best solution seems to be std::from_chars() which does work properly in this situation (and is a better solution in other ways, such as ignoring locale settings which is probably what a library like abieos should do).

However, despite being C++17 std::from_chars<float>() is only present on libstdc++ 11+, and is still completely absent from the latest libc++ 15! So it appears a non-viable option even in the mid-term.

Changing this to strtod() resolves the failure. As @swatanabe has pointed out in a prior conversation on this matter, using strtod() here will increase the rounding error should the string encountered in the JSON not be representable as a float. So even though strtod() otherwise works on other platforms here, I'll ifdef this workaround to just ARM Linux for now.

spoonincode commented 2 years ago

Problem is, since Ubuntu 20 only has gcc 10, it'll probably be ~3 year before we can say Ubuntu 22 is the minimum. Sticking an issue in to stick around for 3+ years :confused: