インサートモードで してファイル名補完を処理した時の動作デバックする時の取っ掛かりbreakpoint
ins_complete() [edit.c:5180] 辺りにbreakpointをセットする。

 5176         else if (ctrl_x_mode == CTRL_X_FILES)
 5177         {
 5178             while (--startcol >= 0 && vim_isfilec(line[startcol]))
 5179                 ;
 5180             compl_col += ++startcol;
 5181             compl_length = (int)curs_col - startcol;
 5182             compl_pattern = addstar(line + compl_col, compl_length,
 5183                                                                 EXPAND_FILES);

b pathcmp してインサートモードで ファイル名補完を開始してbreakした時のバックトレース

(gdb) bt
#0  pathcmp (p=0x23e4ba0 "J4.txt", q=0x23e4bc0 "I1.txt", maxlen=-1)
    at misc2.c:6102
#1  0x00000000004d9758 in pstrcmp (a=0x23e4aa8, b=0x23e4ab0) at misc1.c:9787
#2  0x0000003346637d72 in msort_with_tmp.part.0 () from /lib64/libc.so.6
#3  0x0000003346637b5a in msort_with_tmp.part.0 () from /lib64/libc.so.6
#4  0x0000003346637b44 in msort_with_tmp.part.0 () from /lib64/libc.so.6
#5  0x00000033466380ac in qsort_r () from /lib64/libc.so.6
#6  0x00000000004d9eb9 in unix_expandpath (gap=0x7fff0da465a0, path=
    0x23e46a0 "*", wildoff=0, flags=43, didstar=0) at misc1.c:10001
#7  0x000000000051de2a in mch_expandpath (gap=0x7fff0da465a0, path=
    0x23e46a0 "*", flags=43) at os_unix.c:5471
#8  0x00000000004db08e in gen_expand_wildcards (num_pat=1, pat=0x855008,
    num_file=0x7fff0da46674, file=0x7fff0da46678, flags=43) at misc1.c:10577
#9  0x00000000004d9427 in expand_wildcards (num_pat=1, pat=0x855008, num_file=
    0x7fff0da46674, file=0x7fff0da46678, flags=43) at misc1.c:9323
#10 0x0000000000428ae8 in ins_compl_get_exp (ini=0x855020) at edit.c:4333
#11 0x0000000000429759 in ins_compl_next (allow_get_expansion=1, count=1,
    insert_match=1) at edit.c:4707
#12 0x000000000042ac9e in ins_complete (c=6) at edit.c:5378
#13 0x0000000000423cfb in edit (cmdchar=105, startln=0, count=1) at edit.c:1402
#14 0x00000000004fcc69 in invoke_edit (cap=0x7fff0da46980, repl=0, cmd=105,
    startln=0) at normal.c:9218
#15 0x00000000004fcc02 in nv_edit (cap=0x7fff0da46980) at normal.c:9191
#16 0x00000000004eeed7 in normal_cmd (oap=0x7fff0da46a50, toplevel=1)
    at normal.c:1199
#17 0x00000000005ca166 in main_loop (cmdwin=0, noexmode=0) at main.c:1322
#18 0x00000000005c9ac3 in main (argc=11, argv=0x7fff0da46d88) at main.c:1013

7.3.1004で nfa_regcomp_start() にbreak張って

/\_.*

したときのback trace.

(gdb) bt
#0  nfa_regcomp_start (expr=0xfbad00 "\\_.*", re_flags=1) at regexp_nfa.c:229
#1  0x0000000000543e07 in nfa_regcomp (expr=0xfbad00 "\\_.*", re_flags=1)
    at regexp_nfa.c:3664
#2  0x0000000000544217 in vim_regcomp (expr_arg=0xfbad00 "\\_.*", re_flags=1)
    at regexp.c:7827
#3  0x0000000000556fb5 in search_regcomp (pat=0xfbad00 "\\_.*", pat_save=0,
    pat_use=2, options=0, regmatch=0x7fff7ddfab40) at search.c:216
#4  0x0000000000557925 in searchit (win=0xfa40c0, buf=0xfa59b0, pos=
    0x7fff7ddfad80, dir=1, pat=0xfbad00 "\\_.*", count=1, options=12, pat_use=
    2, stop_lnum=0, tm=0x0) at search.c:560
#5  0x0000000000558f68 in do_search (oap=0x7fff7ddfaf70, dirc=47, pat=
    0xfbad04 "", count=1, options=542, tm=0x0) at search.c:1356
#6  0x00000000004fa4bc in normal_search (cap=0x7fff7ddfaea0, dir=47, pat=
    0xfbad00 "\\_.*", opt=512) at normal.c:6433
#7  0x00000000004fa40b in nv_search (cap=0x7fff7ddfaea0) at normal.c:6400
#8  0x00000000004f13e1 in normal_cmd (oap=0x7fff7ddfaf70, toplevel=1)
    at normal.c:1200
#9  0x00000000005d7652 in main_loop (cmdwin=0, noexmode=0) at main.c:1329
#10 0x00000000005d6faf in main (argc=7, argv=0x7fff7ddfb2a8) at main.c:1020

↑の続き。gdbでcして無限ループに陥った状態で ctrl-c で止めた時の back trace

(gdb) bt
#0  0x0000000000541c2a in nfa_regmatch (start=0xfef2f0, submatch=
    0x7fff7ddfa810, m=0x7fff7ddfa630) at regexp_nfa.c:2989
#1  0x00000000005439ad in nfa_regtry (start=0xfef2f0, col=0)
    at regexp_nfa.c:3528
#2  0x0000000000543dc4 in nfa_regexec_both (line=0xfe064f "", col=0)
    at regexp_nfa.c:3636
#3  0x0000000000544145 in nfa_regexec_multi (rmp=0x7fff7ddfab40, win=0xfa40c0,
    buf=0xfa59b0, lnum=1, col=0, tm=0x0) at regexp_nfa.c:3843
#4  0x000000000054431e in vim_regexec_multi (rmp=0x7fff7ddfab40, win=0xfa40c0,
    buf=0xfa59b0, lnum=1, col=0, tm=0x0) at regexp.c:7918
#5  0x0000000000557b7c in searchit (win=0xfa40c0, buf=0xfa59b0, pos=
    0x7fff7ddfad80, dir=1, pat=0xfbad00 "\\_.*", count=1, options=12, pat_use=
    2, stop_lnum=0, tm=0x0) at search.c:639
#6  0x0000000000558f68 in do_search (oap=0x7fff7ddfaf70, dirc=47, pat=
    0xfbad04 "", count=1, options=542, tm=0x0) at search.c:1356
#7  0x00000000004fa4bc in normal_search (cap=0x7fff7ddfaea0, dir=47, pat=
    0xfbad00 "\\_.*", opt=512) at normal.c:6433
#8  0x00000000004fa40b in nv_search (cap=0x7fff7ddfaea0) at normal.c:6400
#9  0x00000000004f13e1 in normal_cmd (oap=0x7fff7ddfaf70, toplevel=1)
    at normal.c:1200
#10 0x00000000005d7652 in main_loop (cmdwin=0, noexmode=0) at main.c:1329
#11 0x00000000005d6faf in main (argc=7, argv=0x7fff7ddfb2a8) at main.c:1020