Rでデバッグ：R+Emacs+GDB

前に作成した df_make.c を以下のようにコンパイルする

$ MAKEFLAGS="CFLAGS=-g" R CMD SHLIB df_make.c
Windowsの場合
> R CMD SHLIB -d df_make.c

コマンドラインなら R -d gdb あるいは Emacs なら C-u M-x R として引数を -d gdb で指定

(gdb) run

> dyn.load("df_make.so")
> .Call("dfmake", as.character("石田"),as.character("山田"),as.character("加藤"))
  Term Freq
1 石田   10
2 山田   20
3 加藤   30
> 

とりあえず動くのは確認

>   C-c C-c
Program received signal SIGINT, Interrupt.
0x00007ffff716cfd3 in select () from /lib/libc.so.6
(gdb) 
(gdb) b dfmake
Breakpoint 1 at 0x7fffef994b11: file df_make.c, line 12.
(gdb) signal 0
Continuing with no signal.
>

関数 dfmake にブレークポイントを挿入した

> .Call("dfmake", as.character("石田"),as.character("山田"),as.character("加藤"))

Breakpoint 1, dfmake (x=0x1653b78, y=0x1653ba8, z=0x1653bd8) at df_make.c:12
12	  int pc=0;
(gdb) where
#0  dfmake (x=0x1653b78, y=0x1653ba8, z=0x1653bd8) at df_make.c:12
#1  0x00007ffff78e34dc in do_dotcall (call=0x14b4ab0, op=<value optimized out>, args=0x607918, 
    env=<value optimized out>) at dotcode.c:846
#2  0x00007ffff7914c93 in Rf_eval (e=<value optimized out>, rho=<value optimized out>) at eval.c:508
#3  0x00007ffff794a66a in Rf_ReplIteration (rho=0x64e8b0, savestack=0, browselevel=<value optimized out>, 
    state=0x7fffffffd550) at main.c:257
#4  0x00007ffff794a8f9 in R_ReplConsole (rho=0x64e8b0, savestack=0, browselevel=0) at main.c:306
#5  0x00007ffff794ae30 in run_Rmainloop () at main.c:1009
#6  0x000000000040092b in main (ac=<value optimized out>, av=<value optimized out>) at Rmain.c:32
#7  0x00007ffff70acc4d in __libc_start_main () from /lib/libc.so.6
#8  0x0000000000400819 in _start ()
(gdb) n
15	  const char* xx = CHAR(STRING_ELT(x, 0));//解析対象文字列
(gdb) n
16	  const char* yy = CHAR(STRING_ELT(y, 0));//解析対象文字列	
(gdb) n
17	  const char* zz = CHAR(STRING_ELT(z, 0));//解析対象文字列	

(gdb) p R_inspect(x)
@1ae7698 16 STRSXP g0c1 [NAM(2)] (len=1, tl=0)
  @1ae7518 09 CHARSXP g0c1 [gp=0x28] "石田"
$3 = (struct SEXPREC *) 0x1ae7698
(gdb) p xx

$1 = 0x1ae7540 "石田"
(gdb) n
19	  PROTECT(df = allocVector(VECSXP, 2));// ベクトル要素を二つ持つ data.frame

(gdb) info locals
pc = 0
df = 0x14b4ab0
varlabels = 0x7ffff7ddbbe8
tmp = 0x607918
row_names = 0xaefabc970ca4e100
xx = 0x1ae7540 "石田"
yy = 0x1ae75a0 "山田"
zz = 0x1ae7660 "加藤"

(gdb) set var zz ="さとう" // 値を変更
(gdb) info locals
pc = 0
df = 0x14b4ab0
varlabels = 0x7ffff7ddbbe8
tmp = 0x607918
row_names = 0xaefabc970ca4e100
xx = 0x1ae7540 "石田"
yy = 0x1ae75a0 "山田"
zz = 0xa63ad0 "さとう"
(gdb) n
20	  pc++;

(gdb) b 54           // ブレークポイントを 54 行目に
Breakpoint 2 at 0x7fffef994ec2: file df_make.c, line 54.
(gdb) c
Continuing.

Breakpoint 2, dfmake (x=0x1653b78, y=0x1653ba8, z=0x1653bd8) at df_make.c:54
54	  UNPROTECT(pc);

(gdb) p df
$2 = (SEXP) 0x164f160
(gdb) p R_PV(df)
    Term Freq
1   石田   10
2   山田   20
3 さとう   30
$3 = void

(gdb) p Rf_PrintValue(df)
    Term Freq
1   石田   10
2   山田   20
3 さとう   30
$4 = void

(gdb) p Rf_PrintValue(df->attrib)
$class
[1] "data.frame"

$names
[1] "Term" "Freq"

$row.names
[1] "1" "2" "3"

$5 = void

(gdb) p df
$6 = (SEXP) 0xe83098
(gdb) p *df //素の構造
$7 = {sxpinfo = {type = 19, obj = 1, named = 0, gp = 0, mark = 0, debug = 0, trace = 0, spare = 0, 
    gcgen = 0, gccls = 2}, attrib = 0xda3818, gengc_next_node = 0xe830d0, gengc_prev_node = 0xe83060, u = {
    primsxp = {offset = 2}, symsxp = {pname = 0x2, value = 0x1a067b0, internal = 0xe830d0}, listsxp = {
      carval = 0x2, cdrval = 0x1a067b0, tagval = 0xe830d0}, envsxp = {frame = 0x2, enclos = 0x1a067b0, 
      hashtab = 0xe830d0}, closxp = {formals = 0x2, body = 0x1a067b0, env = 0xe830d0}, promsxp = {
      value = 0x2, expr = 0x1a067b0, env = 0xe830d0}}}

(gdb) c // あるいは signal 0 
Continuing.
    Term Freq
1   石田   10
2   山田   20
3 さとう   30
>