Bug 5818 – 64bit ASM can't have 32-bit stack operands

This is a question rolled into a report (it's affecting me, at least). This excerpt (in core/thread.d for D2; in gc/gcx.d for D1 and D2) - the "push EAX" instruction is not legal x86_64 asm code - according to the GNU 64bit Assembler, which is strong enough an argument for me to follow - so is not compilable with the GDC 64bit compiler (and maybe LDC too). asm { push RAX ; push RBX ; push RCX ; push RDX ; push RSI ; push RDI ; push RBP ; push R8 ; push R9 ; push R10 ; push R11 ; push R12 ; push R13 ; push R14 ; push R15 ; --> push EAX ; // 16 byte align the stack <-- This line causes the error mov sp[RBP],RSP ; } So, what to do? Well, first I think druntime should consider revising this code for a start. And secondly, DMD should be hardened to catch and disallow this. Some thoughts for how to change it: In 32bit mode: pusha (afaik) saves (e)ax, cx, dx, bx, sp, bp, si, di popa restores (e)di, si, bp, bx, dx, cx, ax (note, stack is not popped) In GCC builtins: unwind_init (what is currently being used in place of the above illegal code in GDC) saves only the rbx, r12, r13, r14 and r15 registers. Regards

Infact, examining an object jump output DMD emits a push to RAX, not EAX - so this is just dumb.

Fixed: https://github.com/D-Programming-Language/druntime/commit/d3d75983cdd36622ce02338988c35b0ba8b445e9#src/gc/gcx.d DMD also fixed across several commits that greatly improved the accuracy/strictness of the inline assembler checking for 64 bit code.