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http://bugs.exim.org/show_bug.cgi?id=565
Summary: Not an empty string with pcre_copy_named_substring for
unmatched duplicate names
Product: PCRE
Version: 7.2
Platform: Macintosh
OS/Version: All
Status: NEW
Severity: bug
Priority: medium
Component: Code
AssignedTo: ph10@???
ReportedBy: kris.gybels@???
CC: pcre-dev@???
The PCRE API documentation describes the following in the section "DUPLICATE
SUBPATTERN NAMES":
When duplicates are present, pcre_copy_named_substring() and
pcre_get_named_substring() return the first substring corresponding to the
given name that is set. If none are set, an empty string is returned.
However, I found that the code below gives results that seem to contradict the
above. The code matches a string "qux" against the regular expression
"(?<field>foo)|(?<field>bar)". It then gets the value of the named pattern
"field" in a variable field_value, which was previously assigned to hold the
string "ERR". Based on the above description, since "field" has not been
matched, I would expect pcre_copy_named_substring to set field_value[0] to 0,
so that it contains an empty string. But this does not seem to be the case.
Maybe I just misinterpreted the documentation? If my interpretation of the
documentation is correct, I would personally rather see the code fixed to
matched the documentation than the other way around. I think setting the return
string to be empty in case of an unmatched duplicate name makes sense, at least
for the way I have been using the PCRE library.
The full code:
void bug_report()
{
int error_code;
int error_offset;
char * error_description;
pcre * compiled_regexp;
int captured_subpatterns[3*3];
int number_of_substrings;
char field_value[4] = "ERR";
char * match_string = "qux";
int return_value;
compiled_regexp = pcre_compile2("(?<field>foo)|(?<field>bar)",
PCRE_DUPNAMES, &error_code, (const char **) &error_description, &error_offset,
NULL);
number_of_substrings = pcre_exec(compiled_regexp, NULL, match_string,
3, 0, 0, captured_subpatterns, 3*3);
return_value = pcre_copy_named_substring(compiled_regexp, match_string,
captured_subpatterns, number_of_substrings, "field", field_value, 4);
printf("Return value is %i, value of field is: [%s]", return_value,
field_value);
}
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