Hello,
during testing of LTO on a gentoo machine:
Linux qemubox 3.12.13-gentoo #2 SMP Fri Mar 28 22:30:38 Local time zone must be set--see zic x86_64 Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz GenuineIntel GNU/Linux
Configure detects:
checking for __builtin_setjmp... yes
checking for setjmp type... __builtin_setjmp
Problem is that ruby calls longjmp with value greater than 1, e.g. TAG_RAISE (0x6). With -flto compiler proves that __builtin_longjmp is always called with such a value and following errors are displayed:
eval.c: In function ‘rb_jump_tag’:
eval.c:668:5: error: ‘__builtin_longjmp’ second argument must be 1
JUMP_TAG(tag);
^
thread.c: In function ‘rb_threadptr_to_kill’:
thread.c:1887:5: error: ‘__builtin_longjmp’ second argument must be 1
TH_JUMP_TAG(th, TAG_FATAL);
^
vm.c: In function ‘vm_exec’:
vm.c:1413:3: error: ‘__builtin_longjmp’ second argument must be 1
JUMP_TAG(state);
^
eval.c: In function ‘setup_exception’:
eval.c:437:34: error: ‘__builtin_longjmp’ second argument must be 1
if (INTERNAL_EXCEPTION_P(mesg)) JUMP_TAG(TAG_FATAL);
^
eval.c:502:2: error: ‘__builtin_longjmp’ second argument must be 1
JUMP_TAG(TAG_FATAL);
^
eval.c: In function ‘rb_raise_jump’:
eval.c:662:5: error: ‘__builtin_longjmp’ second argument must be 1
JUMP_TAG(TAG_RAISE);
^
eval.c: In function ‘rb_longjmp’:
eval.c:521:5: error: ‘__builtin_longjmp’ second argument must be 1
JUMP_TAG(tag);
^
gc.c: In function ‘rb_memerror’:
gc.c:3417:2: error: ‘__builtin_longjmp’ second argument must be 1
JUMP_TAG(TAG_RAISE);
^
In LTO the compiler proves that function t is never used and so that the function is discarded. That introduces problem in configuration, because __builtin_longjmp must be always called with 1 constant.
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