$ gdb luatex 8477
GNU gdb (GDB) 7.2-ubuntu
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Reading symbols from /usr/bin/luatex...Reading symbols from /usr/lib/debug/usr/bin/luatex...done.
done.
Attaching to program: /usr/bin/luatex, process 8477
Reading symbols from /lib/libpng12.so.0...(no debugging symbols found)...done.
Loaded symbols for /lib/libpng12.so.0
Reading symbols from /lib/libz.so.1...(no debugging symbols found)...done.
Loaded symbols for /lib/libz.so.1
Reading symbols from /lib/libdl.so.2...Reading symbols from /usr/lib/debug/lib/libdl-2.12.1.so...done.
done.
Loaded symbols for /lib/libdl.so.2
Reading symbols from /usr/lib/libstdc++.so.6...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libstdc++.so.6
Reading symbols from /lib/libm.so.6...Reading symbols from /usr/lib/debug/lib/libm-2.12.1.so...done.
done.
Loaded symbols for /lib/libm.so.6
Reading symbols from /lib/libgcc_s.so.1...(no debugging symbols found)...done.
Loaded symbols for /lib/libgcc_s.so.1
Reading symbols from /lib/libc.so.6...Reading symbols from /usr/lib/debug/lib/libc-2.12.1.so...done.
done.
Loaded symbols for /lib/libc.so.6
Reading symbols from /lib64/ld-linux-x86-64.so.2...Reading symbols from /usr/lib/debug/lib/ld-2.12.1.so...done.
done.
Loaded symbols for /lib64/ld-linux-x86-64.so.2
0x00000000004a24d1 in get_avail () at ../../../source/texk/web2c/luatexdir/tex/textoken.w:154
154	../../../source/texk/web2c/luatexdir/tex/textoken.w: No such file or directory.
	in ../../../source/texk/web2c/luatexdir/tex/textoken.w
(gdb) bt full
#0  0x00000000004a24d1 in get_avail () at ../../../source/texk/web2c/luatexdir/tex/textoken.w:154
        p = 273242622
        t = 273242621
#1  0x0000000000471ded in macro_call () at ../../../source/texk/web2c/luatexdir/tex/expand.w:658
        r = 273242622
        p = 273242621
        q = 273242622
        s = -2109026328
        t = <value optimised out>
        u = 1572864
        v = <value optimised out>
        rbrace_ptr = <value optimised out>
        n = <value optimised out>
        unbalance = 9
        m = 257
        ref_count = 163662
        save_scanner_status = 0
        save_warning_index = 3331
        match_chr = 35
#2  0x0000000000472a45 in get_x_token () at ../../../source/texk/web2c/luatexdir/tex/expand.w:384
No locals.
#3  0x0000000000511819 in test_for_cs () at ../../../source/texk/web2c/luatexdir/tex/conditional.w:176
        m = <value optimised out>
        s = <value optimised out>
        p = 526371
#4  conditional () at ../../../source/texk/web2c/luatexdir/tex/conditional.w:483
        b = <value optimised out>
        r = <value optimised out>
        m = <value optimised out>
        n = <value optimised out>
        p = <value optimised out>
---Type <return> to continue, or q <return> to quit---
        q = <value optimised out>
        save_scanner_status = <value optimised out>
        save_cond_ptr = 74229
        this_if = <value optimised out>
#5  0x0000000000472695 in expand () at ../../../source/texk/web2c/luatexdir/tex/expand.w:236
        t = <value optimised out>
        p = <value optimised out>
        cur_ptr = <value optimised out>
        cv_backup = 1
        cvl_backup = 0
        radix_backup = 0
        co_backup = 0
        backup_backup = 0
        save_scanner_status = 0
#6  0x0000000000472a7d in get_x_token () at ../../../source/texk/web2c/luatexdir/tex/expand.w:391
No locals.
#7  0x000000000048022d in main_control () at ../../../source/texk/web2c/luatexdir/tex/maincontrol.w:892
No locals.
#8  0x0000000000477fa7 in main_body () at ../../../source/texk/web2c/luatexdir/tex/mainbody.w:469
        pdftex_map = "pdftex.map"
#9  0x000000000045818e in main (ac=<value optimised out>, av=<value optimised out>)
    at ../../../source/texk/web2c/luatexdir/luatex.c:460
No locals.
(gdb) info registers
rax            0x104959fe	273242622
rbx            0x104959fd	273242621
rcx            0x104959fe	273242622
rdx            0x2b80e8bbc010	47832660426768
rsi            0x136f35e2	326055394
rdi            0x2b8184356f28	47835268869928
rbp            0x9	0x9
rsp            0x7fff97386740	0x7fff97386740
r8             0x28	40
r9             0x180000	1572864
r10            0x0	0
r11            0x2b80e6dff0b1	47832629244081
r12            0x13fa88	1309320
r13            0x101	257
r14            0x27f4e	163662
r15            0x824acfe8	2185940968
rip            0x4a24d1	0x4a24d1 <get_avail+49>
eflags         0x10202	[ IF RF ]
cs             0x33	51
ss             0x2b	43
ds             0x0	0
es             0x0	0
fs             0x0	0
gs             0x0	0
(gdb) x/16i $pc
=> 0x4a24d1 <get_avail+49>:	movl   $0x0,0x4(%rdx,%rcx,8)
   0x4a24d9 <get_avail+57>:	addl   $0x1,0x963a88(%rip)        # 0xe05f68 <dyn_used>
   0x4a24e0 <get_avail+64>:	pop    %rbx
   0x4a24e1 <get_avail+65>:	retq   
   0x4a24e2 <get_avail+66>:	jmp    0x4a24e8 <get_avail+72>
   0x4a24e4 <get_avail+68>:	nop
   0x4a24e5 <get_avail+69>:	nop
   0x4a24e6 <get_avail+70>:	nop
   0x4a24e7 <get_avail+71>:	nop
   0x4a24e8 <get_avail+72>:	mov    %esi,%eax
   0x4a24ea <get_avail+74>:	mov    $0xcccccccd,%ebx
   0x4a24ef <get_avail+79>:	mov    0x963a6a(%rip),%rdi        # 0xe05f60 <fixmem>
   0x4a24f6 <get_avail+86>:	mul    %ebx
   0x4a24f8 <get_avail+88>:	mov    %edx,%ebx
   0x4a24fa <get_avail+90>:	shr    $0x2,%ebx
   0x4a24fd <get_avail+93>:	lea    0x1(%rbx,%rsi,1),%esi
(gdb) thread apply all backtrace

Thread 1 (process 8477):
#0  0x00000000004a24d1 in get_avail () at ../../../source/texk/web2c/luatexdir/tex/textoken.w:154
#1  0x0000000000471ded in macro_call () at ../../../source/texk/web2c/luatexdir/tex/expand.w:658
#2  0x0000000000472a45 in get_x_token () at ../../../source/texk/web2c/luatexdir/tex/expand.w:384
#3  0x0000000000511819 in test_for_cs () at ../../../source/texk/web2c/luatexdir/tex/conditional.w:176
#4  conditional () at ../../../source/texk/web2c/luatexdir/tex/conditional.w:483
#5  0x0000000000472695 in expand () at ../../../source/texk/web2c/luatexdir/tex/expand.w:236
#6  0x0000000000472a7d in get_x_token () at ../../../source/texk/web2c/luatexdir/tex/expand.w:391
#7  0x000000000048022d in main_control () at ../../../source/texk/web2c/luatexdir/tex/maincontrol.w:892
#8  0x0000000000477fa7 in main_body () at ../../../source/texk/web2c/luatexdir/tex/mainbody.w:469
#9  0x000000000045818e in main (ac=<value optimised out>, av=<value optimised out>)
    at ../../../source/texk/web2c/luatexdir/luatex.c:460
(gdb)