[555aaditya]

NumberParser::parse("+-5") returns -5. Since #5301, strToInt() skips a leading + and passes the rest to std::from_chars, which accepts a - for signed types. So +-5 (and, for signed types, +-ff in base 16) is accepted as a negative number. The digit loop before #5301 rejected it.

• Foundation/include/Poco/NumericString.h: strToInt() returns false when a - follows the skipped +. A single leading + or - is handled as before.

Tests: StringTest::stringToInt<T>() (all integer types, base 10 and 16) and NumberParserTest::testParseError assert that +-123 is rejected. Both fail without the change and pass with it.

Validation on macOS arm64, Apple clang 21, Debug, ENABLE_COMPILER_WARNINGS=ON (no warnings in the changed file):

• the full Foundation suite with -ignore cppignore.lnx (1004 tests, OK);
• StringTest and NumberParserTest under ASan, and StringTest::testStringToInt and NumberParserTest under UBSan;
• clang-tidy and cppcheck, no findings on the changed lines.

Under UBSan, StringTest::conversionBenchmarks aborts on a signed overflow of gSink in StringTest.cpp:1492. It does the same on main without this change.

Follow-up: the comment in XSD/CodeGen/src/BuiltinTypes.cpp gives "+-5" as an example. The check there is still needed for leading whitespace.

[Copilot]

🟢 Approval recommended

The narrowly scoped guard safely rejects malformed signs and includes regression coverage at both conversion and public API levels.

No open issues 🎉

What changed in this PR

Fixes an integer-parsing regression introduced by #5301 by rejecting a minus sign immediately after a leading plus sign, while preserving valid single-sign inputs.

Changes:

• Adds a targeted guard in strToInt() for malformed +- prefixes.
• Adds regression tests for decimal and hexadecimal conversion and the public NumberParser::parse() API.

File	Description
Foundation/​testsuite/​src/​StringTest.h	Tests rejection of +-123 in bases 10 and 16 across integer types.
Foundation/​testsuite/​src/​NumberParserTest.cpp	Verifies that NumberParser::parse("+-123") throws SyntaxException.
Foundation/​include/​Poco/​NumericString.h	Rejects a minus sign after a skipped leading plus sign.

_{Review effort: Balanced}