Re: recent master core dumps building on FreeBSD i386

[Paul Eggert]

On 10/18/18 9:02 AM, Eli Zaretskii wrote:
> Can you please repeat this experiment, and then, when it crashes, do
> this:
>
>    (gdb) source ./.gdbinit
>    (gdb) frame 2
>    (gdb) p/x a
>    (gdb) xtype
>
> and show us the results?

Also, please try these GDB commands when debugging ./temacs:

b syms_of_threads
r -Q
p &main_thread
disas syms_of_threads
p &Vmain_thread

I'm attaching the output of these commands on Fedora 28 x86-64 compiled 
with 'gcc -m32 -march=native -g3 -O2' (AMD Phenom II X4 910e). Evidently 
your compiler (clang?) is not inlining make_lisp_ptr, but it's still 
useful to know what it's up to. I see that GCC optimizes away not only 
the call to make_lisp_ptr, but also the runtime check 'TAGGEDP (a, type) 
&& XUNTAG (a, type, char) == ptr', I guess because GCC knows that 
main_thread is properly aligned so TAGGEDP must succeed here. clang 
isn't smart enough to do this sort of optimization (at least on Fedora) 
so if you're using clang that might partly explain the problem.

Also, please investigate what the macro GCALIGNED_STRUCT expands to. You 
can use 'gcc -E' to do that.

gdb.txt
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