ext/iconv/iconv.c: remove incorrect //IGNORE handling

Some iconv implementations allow you to append "//IGNORE" to the
target charset as an indication that it should skip certain
conversions. This is true for the two GNU iconv implementations, and
is apparently based on a Solaris extension. It has also recently been
added to POSIX 2024. Specifically, //IGNORE will cause iconv() to skip
input sequences that are valid but cannot be translated to the target
charset. It does not skip sequences that are invalid inputs; these
still cause an EILSEQ.

There is a minimal check for "//IGNORE" in ext/iconv/iconv.c, based on
a config.m4 check for ICONV_BROKEN_IGNORE. If the iconv implementation
does not support "//IGNORE", PHP will check for it in the target
charset string, and will attempt its own workaround. This workaround
is wrong for two reasons:

  1. The string "//IGNORE" is left in the target charset, so if the
     current iconv implementation doesn't understand it, it's just
     going to fail. This is what happens on musl.

  2. The PHP workaround looks for EILSEQ, and then attempts to skip
     the untranslatable sequence. But with non-GNU iconvs (i.e. all
     affected implementations), this will be backwards. In non-GNU
     implementations, EILSEQ is raised only for invalid input
     sequences, and not for untranslatable ones. Even in POSIX 2024,
     EILSEQ is reserved for input sequences that are invalid rather
     than untranslatable. In other words, sequences that cause an
     EILSEQ should never be ignored.

This commit removes the workaround. It's not quite right, and removing
it doesn't cause any new test failures on musl. It would be nice if
PHP could abstract the //IGNORE magic away from the user, but since it
has been added to POSIX 2024, I think the simplest thing to do is wait
it out. Eventually the other implementations will add support for it,
and then there will be no need to work around its absence.

Author: orlitzky

ext/iconv/iconv.c

@@ -415,24 +415,6 @@ static php_iconv_err_t _php_iconv_appendc(smart_str *d, const char c, iconv_t cd
 }
 /* }}} */
 
-/* {{{ */
-#ifdef ICONV_BROKEN_IGNORE
-static int _php_check_ignore(const char *charset)
-{
-	size_t clen = strlen(charset);
-	if (clen >= 9 && strcmp("//IGNORE", charset+clen-8) == 0) {
-		return 1;
-	}
-	if (clen >= 19 && strcmp("//IGNORE//TRANSLIT", charset+clen-18) == 0) {
-		return 1;
-	}
-	return 0;
-}
-#else
-#define _php_check_ignore(x) (0)
-#endif
-/* }}} */
-
 /* {{{ php_iconv_string() */
 PHP_ICONV_API php_iconv_err_t php_iconv_string(const char *in_p, size_t in_len, zend_string **out, const char *out_charset, const char *in_charset)
 {
@@ -442,7 +424,6 @@ PHP_ICONV_API php_iconv_err_t php_iconv_string(const char *in_p, size_t in_len,
 	size_t bsz, result = 0;
 	php_iconv_err_t retval = PHP_ICONV_ERR_SUCCESS;
 	zend_string *out_buf;
-	int ignore_ilseq = _php_check_ignore(out_charset);
 
 	*out = NULL;
 
@@ -466,16 +447,6 @@ PHP_ICONV_API php_iconv_err_t php_iconv_string(const char *in_p, size_t in_len,
 		result = iconv(cd, (ICONV_CONST char **) &in_p, &in_left, (char **) &out_p, &out_left);
 		out_size = bsz - out_left;
 		if (result == (size_t)(-1)) {
-			if (ignore_ilseq && errno == EILSEQ) {
-				if (in_left <= 1) {
-					result = 0;
-				} else {
-					errno = 0;
-					in_p++;
-					in_left--;
-					continue;
-				}
-			}
 
 			if (errno == E2BIG && in_left > 0) {
 				/* converted string is longer than out buffer */