On 25 July 2018 at 12:05, Mike Franklin via D.gnu <d.gnu@puremagic.com> wrote: > On Wednesday, 25 July 2018 at 08:37:28 UTC, Zheng (Vic) Luo wrote: > >> Current implementation of compilers assumes the existence of some symbols >> from libc, which leads to an infinite loop if we want to implement >> primitives like "memset" with our own code because the compiler will >> optimize consecutive set with "memset". This suggests that we cannot write a >> freestanding program without supports from compiler. With "-betterC" flag, >> dmd/gdc/ldc also come into this issue[5], which also applies to C/C++[1] and >> rust [2][3][4]. > > > GDC doesn't seem to be affected. See https://explore.dgnu.org/g/ZJVjAu > i.e. no recursive calls to `memset`, but I don't know if I just got lucky > with my implementation. > >> It would be better to provide a standard flag like "-ffreestanding" (or >> -fno-builtin?) to disable such optimizations to facilitate freestanding >> programming instead of forcing the developers to hack around different >> compiler implementations, so I was wondering is there any progress on this >> problem? > > > According to https://wiki.dlang.org/Using_GDC, `-fno-builtin` is already > there. >
It only goes as far as not recognizing user declared functions as being built-in. The compiler may still generate builtin calls internally, and you may explicitly call any function in the gcc.builtins module. Iain.
