TCLAP 1.4.0 - changes since 1.2.5

This summary compares TCLAP 1.4.0 with the v1.2.5 tag, not with an earlier 1.4 release candidate. TCLAP remains a header-only library supporting C++98.

Arguments and constraints

• Argument groups replace the old XOR handler: OneOf requires exactly one member, EitherOf permits at most one, and AnyOf groups arguments for display without imposing a selection rule. CmdLine::xorAdd remains as a deprecated convenience; new code should use OneOf. Exclusive members must be optional.
• Argument aliases provide equivalent short flags and long names for one argument, sharing its value, visitor, constraints and group membership. Registration rejects conflicting spellings; detailed help lists aliases.
• PredicateConstraint adapts owned functions and function objects to value constraints. MakeConstraint and MakeRuleConstraint provide factories, with fixed help text or text computed from the stored rule. Null function pointers are rejected at construction.
• Inclusive RangeConstraint and ready-made less-than/greater-than constraints provide ordered bounds, reject unordered comparisons and generate error/help text. Constraints can be passed as const objects; ValuesConstraint accepts a const collection.
• Arguments can be hidden from help while remaining available for parsing.

Help, output and documentation

• Usage follows BSD-style conventions, with clearer required/optional and exclusive groups, type placeholders, and positional arguments shown in parsing order. Empty combined-switch summaries are omitted.
• Improved wrapping, multiline descriptions and handling of long program names; fixed crashes and buffer/length errors in help formatting. Displayed program names omit directory paths and the executable suffix.
• Built-in help, version and error messages support application-provided translation, with a gettext integration example.
• DocBook output supports argument groups, ordered positional operands and aliases, escapes XML data, preserves type labels, and links correctly when included from multiple translation units.
• Updated manual, examples and installation guidance cover parser reuse, borrowed object lifetimes, constraints, end-of-options handling and grouping.

Parsing and robustness

• Delimiters, end-of-options state and optional positional registration checks are scoped to each parser. Reset clears end-of-options state, and positional ordering is checked at registration rather than object construction.
• Failed argument/group registration rolls back parser state and bindings. Duplicate detection uses declared names, flags and aliases rather than descriptions or custom argument equality operators.
• Explicitly empty attached values are passed to the value type: empty strings are accepted, numeric extraction fails, and custom extractors decide their own behavior. Positional arguments invoke their visitors when matched.
• Fixed counted-switch reset and boolean conversion, positional equality, empty argv-vector handling and exception diagnostic storage. Corrected required argument bookkeeping without changing the argument's declared requirement.

Compatibility notes

• Stream-extracted (ValueLike) values reject embedded NUL bytes by default, instead of silently truncating. Define TCLAP_ALLOW_NUL_TRUNCATION=1 before including TCLAP to restore the old behavior; use one setting program-wide. StringLike values, including std::string, retain their string semantics.
• The deprecated mutable ValueArg::getValue() overload, ZshCompletionOutput and XorHandler are removed. Legacy XOR customization helpers are replaced by ArgGroup, and ignore-rest control now belongs to the parser.
• Custom CmdLineInterface implementations and code depending on mutable metadata accessors need adapting to the revised grouping/const interfaces. Help text and some diagnostics differ from 1.2.5; update output comparisons.

Build, installation and testing

• CMake replaces Autotools and requires CMake 3.13 or later. Installed CMake package discovery, pkg-config metadata and CPack packaging are provided; examples, tests and documentation can be disabled independently.
• Out-of-source builds, configurable installation destinations and paths with spaces are supported. Release archives include generated API/manual docs, examples, the test runner, unit tests and fuzz sources/seeds.
• Tests use Python 3 and CTest, with an expanded public-API unit suite and portable C++98 fuzz-seed regression tests. The runner executes the full suite by default and supports selecting a subset. Optional Clang/libFuzzer builds support sanitizer testing.
• GitHub Actions covers Linux GCC/Clang, macOS Clang and Windows MSVC. Updated documentation pages show these workflows and link maintained versions.