Hi, On 2018-10-03 12:54:52 -0400, Tom Lane wrote: > Andres Freund <and...@anarazel.de> writes: > > It seems the general "use strfromd if available" approach is generally > > useful, even if we need to serialize the precision. > > Agreed. > > > Putting it into an > > inline appears to be helpful, avoids some of the otherwise precision > > related branches. Do you have any feelings about which header to put > > the code in? I used common/string.h so far. > > I do not think it should be in a header, for two reasons: > > (1) The need to use sprintf for portability means that we need very > tight constraints on the precision spec *and* the buffer size *and* > the format type (%f pretty much destroys certainty about how long the > output string is). So this isn't going to be general purpose code. > I think just writing it into float[48]out is sufficient.
Well, the numbers suggest it's also useful to do so from snprintf - it's not that rare that we output floating point numbers from semi performance critical code, even leaving aside float[48]out. So I'm not convinced that we shouldn't do this from within snprintf.c too. Now we could open-code it twice, but i'm not sure I see the point. If we just define the API as having to guarantee there's enough space for the output format, I think it'll work well enough for now? snprintf.c already assumes everything floating point can be output in 1024 chars, no? Greetings, Andres Freund
