> To be clear, the error I'm seeing with the example is this: > > /usr/libexec/gcc/arm-3ds-none-eabi/ld: warning: cannot find entry symbol _start; defaulting to 0000000000008018 > /usr/libexec/gcc/arm-3ds-none-eabi/ld: /tmp/ccPp7lyA.ltrans0.ltrans.o: in function `f': > /home/gabriel/tmp/t1.c:3: undefined reference to `malloc' > collect2: error: ld returned 1 exit status I would start by adding -Wl,-y,malloc to last gcc command line (the link step with '-o main') to see how linker sees references to malloc. You can do that both with and without -flto to compare successful/failing scenarios. If you have both BFD and Gold linker, try both (-fuse-ld=gold or =bfd). You can also pass -Wl,-v to see the linker command line and compare it with non-LTO compilation (or even native compilation). Does it work if you pass -fno-builtin-malloc to compilation of t.c? It looks like without the option, GCC LTO plugin does not see malloc as an undefined symbol in t.o, the linker does not unpack malloc from libc, and when LTO plugin passes a new object file that references malloc, it's too late. I believe linkers had some hacks to help this case (rescanning libc for new references from LTO object files), but I'm not exactly sure, it's been a while since I looked at a related area. Alexander
