tcl/changes.md

The source code for Tcl is managed by fossil. Tcl developers coordinate all changes to the Tcl source code at

Tcl Source Code

Release Tcl 9.1a2 arises from the check-in with tag core-9-1-a2.

Highlighted differences between Tcl 9.1 and Tcl 9.0 are summarized below, with focus on changes important to programmers using the Tcl library and writing Tcl scripts.

New commands and options

• New options -backslashes, -commands and -variables for subst command
• New command unicode for Unicode normalization
• New timer command, switch to monotonic clock and microsecond resolution
• Remove expr behavior from lseq Incompatibility
• File paths are now treated as case-insensitive on MacOS Incompatibility
• New command tcl::registry as a synonym for the registry command without needing the registry package to be loaded. The registry module is now part of the core Tcl DLL in all build configurations.
• New lfilter command for selecting items from a list
• Many new functions from C99, specifically: acosh(), asinh(), atanh(), cbrt(), copysign(), dim(), erf(), erfc(), exp2(), expm1(), fma(), gamma(), ldexp(), lgamma(), log1p(), log2(), logb(), nextafter(), remainder(), signbit(), and trunc(), and (for functions that return multiple values in their C99 API) the commands: divmod, frexp, modf, and remquo. (See this page for more information about these functions; the Tcl functions are intentionally only thin wrappers around the functions in the C99 standard.)

New public C API

• Tcl_IsEmpty() — checks if the string representation of a value would be the empty string
• Tcl_GetEncodingNameForUser() — returns name of encoding from user settings
• Tcl_AttemptCreateHashEntry() — version of Tcl_CreateHashEntry() that returns NULL instead of panic'ing on memory allocation errors
• Tcl_ListObjRange(), Tcl_ListObjRepeat(), Tcl_ListObjReverse() — C API for new list operations
• Tcl_UtfToNormalized(), Tcl_UtfToNormalizedDString() — C API for Unicode normalization
• Tcl_UtfToExternalEx() and Tcl_ExternalToUtfEx() — C encoding API supporting output buffers larger than INT_MAX
• New API for monotonic clock and microseconds resolution
• Windows auto_execok enhancements and exec search reform

Changes in interpreter initialization

• Custom applications must call Tcl_FindExecutable or TclZipfs_AppHook to initialize Tcl Potential incompatibility
• Search path for locating Tcl core script and encodings is changed Potential incompatibility

Performance

• Memory efficient internal representations for list operations on large lists.
• Continued 64-bit capacity: Command line arguments larger than 2Gb
• Substantial speedup in interpreter creation
• Support for long paths on Windows

Bug fixes

• Inconsistent glob matching on MacOS
• file normalize does not uniquely identify a file on MacOS
• Inconsistencies between cd and file normalize for volume-relative paths on Windows
• Tcl cannot run from an arbitrary build directory with --disable-zipfs

Updated bundled packages, libraries, standards, data

• Unicode 18.0.0 (draft)