Thank you Winston for the solution! The only workaround I come up with is to
set options(encoding = "UTF-8"), which is generally undesirable.
I'm wondering is there any chance this patch will be included in future R
version? I have been running into this problem from time to time and the
latest R 3.2.1 still hasn't handled this issue properly.
Winston Chang wrote
> After a bit more investigation, I think I've found the cause of the bug,
> and I have a patch.
>
> This bug happens with grep(), when:
> * Running on Windows.
> * The search uses fixed=TRUE.
> * The search pattern is a single byte.
> * The current locale has a multibyte encoding.
>
> ===
> Here's an example that demonstrates the bug:
>
> # First, create a 3-byte UTF-8 character
> y <- rawToChar(as.raw(c(0xe6, 0xb8, 0x97)))
> Encoding(y) <- "UTF-8"
> y
> # [1] "渗"
>
> # In my default locale, grep with a single-char pattern and fixed=TRUE
> # returns integer(0), as expected.
> Sys.getlocale("LC_CTYPE")
> # [1] "English_United States.1252"
> grep("a", y, fixed = TRUE)
> # integer(0)
>
> # When the using a multibyte locale, grep with a single-char
> # pattern and fixed=TRUE results in an error.
> Sys.setlocale("LC_CTYPE", "chinese")
> grep("a", y, fixed = TRUE)
> # Error in grep("a", y, fixed = TRUE) : invalid multibyte string at '<97>'
>
>
> ===
>
> I believe the problem is in the main/grep.c file, in the fgrep_one
> function. It tests for a multi-byte character string locale
> `mbcslocale`, and then for the `use_UTF8`, like so:
>
> if (!useBytes && mbcslocale) {
> ...
> } else if (!useBytes && use_UTF8) {
> ...
> } else ...
>
> This can be seen at
> https://github.com/wch/r-source/blob/e92b4c1cba05762480cd3898335144e5dd111cb7/src/main/grep.c#L668-L692
>
> A similar pattern occurs in the fgrep_one_bytes function, at
> https://github.com/wch/r-source/blob/e92b4c1cba05762480cd3898335144e5dd111cb7/src/main/grep.c#L718-L736
>
>
> I believe that the test order should be reversed; it should test first
> for `use_UTF8`, and then for `mbcslocale`. This pattern occurs in a few
> places in grep.c. It looks like this:
>
> if (!useBytes && use_UTF8) {
> ...
> } else if (!useBytes && mbcslocale) {
> ...
> } else ...
>
>
> ===
> This patch does what I described; it simply tests for `use_UTF8` first,
> and then `mbcslocale`, in both fgrep_one and fgrep_one_bytes. I made
> this patch against the 3.1.2 sources, and tested the example code above.
> In both cases, grep() returned integer(0), as expected.
>
> (The reason I made this change against 3.1.2 is because I had problems
> getting the current trunk to compile on both Linux or Windows.)
>
>
> diff --git src/main/grep.c src/main/grep.c
> index 6e6ec3e..348c63d 100644
> --- src/main/grep.c
> +++ src/main/grep.c
> @@ -664,27 +664,27 @@ static int fgrep_one(const char *pat, const char
> *target,
> }
> return -1;
> }
> -if (!useBytes && mbcslocale) { /* skip along by chars */
> - mbstate_t mb_st;
> +if (!useBytes && use_UTF8) {
> int ib, used;
> - mbs_init(&mb_st);
> for (ib = 0, i = 0; ib <= len-plen; i++) {
> if (strncmp(pat, target+ib, plen) == 0) {
> if (next != NULL) *next = ib + plen;
> return i;
> }
> - used = (int) Mbrtowc(NULL, target+ib, MB_CUR_MAX, &mb_st);
> + used = utf8clen(target[ib]);
> if (used <= 0) break;
> ib += used;
> }
> -} else if (!useBytes && use_UTF8) {
> +} else if (!useBytes && mbcslocale) { /* skip along by chars */
> + mbstate_t mb_st;
> int ib, used;
> + mbs_init(&mb_st);
> for (ib = 0, i = 0; ib <= len-plen; i++) {
> if (strncmp(pat, target+ib, plen) == 0) {
> if (next != NULL) *next = ib + plen;
> return i;
> }
> - used = utf8clen(target[ib]);
> + used = (int) Mbrtowc(NULL, target+ib, MB_CUR_MAX, &mb_st);
> if (used <= 0) break;
> ib += used;
> }
> @@ -714,21 +714,21 @@ static int fgrep_one_bytes(const char *pat, const
> char *target, int len,
> if (*p == pat[0]) return i;
> return -1;
> }
> -if (!useBytes && mbcslocale) { /* skip along by chars */
> - mbstate_t mb_st;
> +if (!useBytes && use_UTF8) { /* not really needed */
> int ib, used;
> - mbs_init(&mb_st);
> for (ib = 0, i = 0; ib <= len-plen; i++) {
> if (strncmp(pat, target+ib, plen) == 0) return ib;
> - used = (int) Mbrtowc(NULL, target+ib, MB_CUR_MAX, &mb_st);
> + used = utf8clen(target[ib]);
> if (used <= 0) break;
> ib += used;
> }
> -} else if (!useBytes && use_UTF8) { /* not really needed */
> +} else if (!useBytes && mbcslocale) { /* skip along by chars */
> + mbstate_t mb_st;
> int ib, used;
> + mbs_init(&mb
