Incorrect Bitwise Check for Newline Mode Causes Regex Matching Failure in POCO RegularExpression

[sdottaka]

Describe the bug
The regular expression "\\s+$" with RegularExpression::RE_MULTILINE | RegularExpression::RE_NEWLINE_ANYCRLF does not correctly remove trailing whitespace at the end of lines. The issue is caused by improper bitwise checks when setting the newline mode in RegularExpression.cpp. As a result, RE_NEWLINE_ANYCRLF is not correctly recognized, leading to incorrect behavior when matching line endings.

To Reproduce
Steps to reproduce the behavior:

1. Compile and run the following test case:

void RegularExpressionTest::testSubst5()
{
    RegularExpression re("\\s+$", RegularExpression::RE_MULTILINE | RegularExpression::RE_NEWLINE_ANYCRLF);
    std::string s = "ABC 123  \n456 789 \nDEF  ";
    assertTrue(re.subst(s, "", RegularExpression::RE_GLOBAL) == 3);
    assertTrue(s == "ABC 123\n456 789\nDEF");
}

2. Observe that the test fails because the expected substitution does not occur.

Expected behavior
The regular expression should correctly remove trailing whitespace at the end of each line, resulting in the string:

ABC 123
456 789
DEF

Logs
No specific logs are generated, but the test assertion fails.

Screenshots
N/A

Please add relevant environment information:

• OS Type and Version: (e.g., Windows 10 64-bit, macOS 12, Ubuntu 22.04)
• POCO Version: (1.14.1)
• Third-party product type and version: (if applicable)

Additional context
The issue is caused by improper bitwise checks in RegularExpression.cpp. The following patch resolves the issue by ensuring that RE_NEWLINE_ANYCRLF is properly detected:

--- a/Foundation/src/RegularExpression.cpp
+++ b/Foundation/src/RegularExpression.cpp
@@ -75,13 +75,14 @@ RegularExpression::RegularExpression(const std::string& pattern, int options, bo
        pcre2_compile_context* context = pcre2_compile_context_create(nullptr);
        if (!context) throw Poco::RegularExpressionException("cannot create compile context");

-       if (options & RE_NEWLINE_LF)
+       const unsigned int RE_NEWLINE_MASK = 0x00f00000;
+       if ((options & RE_NEWLINE_MASK) == RE_NEWLINE_LF)
                pcre2_set_newline(context, PCRE2_NEWLINE_LF);
-       else if (options & RE_NEWLINE_CRLF)
+       else if ((options & RE_NEWLINE_MASK) == RE_NEWLINE_CRLF)
                pcre2_set_newline(context, PCRE2_NEWLINE_CRLF);
-       else if (options & RE_NEWLINE_ANY)
+       else if ((options & RE_NEWLINE_MASK) == RE_NEWLINE_ANY)
                pcre2_set_newline(context, PCRE2_NEWLINE_ANY);
-       else if (options & RE_NEWLINE_ANYCRLF)
+       else if ((options & RE_NEWLINE_MASK) == RE_NEWLINE_ANYCRLF)
                pcre2_set_newline(context, PCRE2_NEWLINE_ANYCRLF);
        else // default RE_NEWLINE_CR
                pcre2_set_newline(context, PCRE2_NEWLINE_CR);

This ensures that only the correct bits are checked when setting the newline mode, fixing the issue.