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

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_TclListObjReverse - 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

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
• Speedup in interpreter creation