On Thu, Jun 05, 2025 at 11:29:27PM +0200, Marc Glisse via Gcc-help wrote: > On Thu, 5 Jun 2025, Nicola Giuliani via Gcc-help wrote: > > >What do you think of this particular problem? Does it make any sense to > >you? Can you tell me how to recover the same behavior at linking time > >without turning on the unsafe math optimizations? > > To understand what is going on, add -v to the compile line. This will show > you how the linker (possibly called collect2 or ld) is invoked. Do it once > with -funsafe-math-optimizations and once without. Look at the diff. > Notice the addition of crtfastmath.o. > (if motivated, look at the source > https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=libgcc/config/i386/crtfastmath.c;hb=HEAD > ) The -ffast-math stuff is needed, because this compiler behaviour is simply incorrect without that: by default we want the compiler to generate code that does follow all relevant standards! Segher
