https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115481
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Georg-Johann Lay from comment #4) > (In reply to dv from comment #0) > > New versions of avrlibc provide long double math functions, > > In the case it matters: > > 1) avr-libc has long double prototypes in math.h since v2.2. Should GCC 14 support older versions of avr-libc? Or can we assume that anybody trying to build libstdc++ (which requires an explicit --enable-libstdcxx for avr) is using a new avr-libc? Fedora 39 only has avr-libc-2.0.0 so my own test build use an older one. > 2a) When long double is a 32-bit type, then the long double functions are > implemented in avr-libc as aliases to float functions. > > 2b) When long double is a 64-bit type, then the long double functions are > implemented in avr-libgcc. This requires GCC v10+ and an appropriate > configuration (default is long long = 64 bit and switchable to 32 bit) > https://gcc.gnu.org/install/configure.html#avr OK, any fixes to libstdc++ here will only be for GCC 12+ (and to be honest, probably only 14+). > 3) The implementations are not complete, for example log2f is missing, gamma > etc. but log2l is available when long long is 64. > > 4) Available multilib variants ([long] double is 32 and / or 64 bits) can be > selected at configure time, and depending on configuration, [long] double > layout can also be selected at compile time (-mdouble=64 etc.).